Endocrinology Flashcards
What hormones are produced by the adenohypophysis?
FSH/LH Prolactin Growth hormone Thyroid stimulating hormone ACTH (Cortisol)
What is a primary endocrine gland disease?
Where the gland itself does not work correctly
e.g. the thyroid of the adrenal gland
What is a secondary endocrine gland disease?
Where the signal from the pituitary gland doesn’t work so the signal is not sent to the gland
What is a tertiary endocrine gland disease?
Where the hypothalamic releasing hormones don’t work: this is not measured clinically
What is panhypopituitarism?
A decreased production of all anterior pituitary hormones or of specific hormones
Can be congenital or acquired
What is congenital panhypopituitarism? How common is it? What causes it? What are the symptoms?
A deficiency in growth hormones and at least 1 more pituitary hormone. It is rare
Usually due to mutations of transcription factor genes needed for normal pituitary development- e.g. PROP1 mutation
Short stature- plus other features
Hypoplastic anterior pituitry gland on MRI
What are the possible causes of acquired panhypopituitarism?
1) Tumours hypothalamic, pituitary 2) Radiation hypothalamic/pituitary damage 3) Infection e.g. meningitis 4) Traumatic brain injury 5) Infiltrative disease often involves pituitary stalk e.g. neurosarcoidosis 6) Inflammatory (hypophysitis) 7) Pituitary apoplexy haemorrhage (or less commonly infarction) 8) Peri-partum infarction (Sheehan's syndrome)
What hormone is deficient in secondary hypogonadism? What are the symptoms?
FSH/LH
Reduced libido
Secondary amenorrhoea
Erectile dysfunction
What hormone is deficient in secondary hypoadrenalism? What are the symptoms?
ACTH (cortisol deficiency)
Fatigue
What hormone is deficient in secondary hypothyroidism? What are the symptoms?
TSH
Fatigue
Weight gain
What is Sheehan’s syndrome? When and why does this occur?
Post-partum hypopituitarism secondary to hypotension (post-partum haemorrhage)- happens around delivery of baby
Less common in developed countries
Adenohypophysis enlarges in pregnancy (lactotroph hyperplasia)
Post-partum haemorrhage leads to pituitary infarction
What is the presentation of Sheehan’s syndrome?
Lethargy, anorexia, weight loss - TSH/ACTH/(GH) deficiency
Failure of lactation - PRL deficiency
Failure to resume menses post-delivery
Posterior pituitary usually not affected
What is pituitary apoplexy? How does it present?
Intra-pituitary haemorrhage or (less commonly) infarction. It is a medical emergency
SEVERE sudden onset headache, visual field defect- compressed optic chiasm (bitemporal hemianopia)
Cavernous sinus involved; may lead to diplopia or ptosis
What properties of the different pituitary hormones makes them difficult to measure?
Cortisol varies depending on the time of day
T4 circulating half-life of 6 days
FSH/LH are cyclical
GH/ACTH are pulsatile
What biochemical tests can you perform for hypopituitarism?
- Basal plasma concentrations of pituitary or target endocrine gland hormones
- Insulin-induced hypoglycaemia stimulates GH and ACTH release
If you are deficient in ACTH what is used as a replacement and what should you check?
Replace: Hydrocortisone
Check: Serum cortisol
If you are deficient in TSH what is used as a replacement and what should you check?
Replace: Thyroxine
Check: Serum free T4
If a woman is deficient in LH/FSH what is used as a replacement and what should you check?
Replace: HRT (E2 plus progestagen)
Check: Symptom improvement, withdrawal bleeds
If a man is deficient in LH/FSH what is used as a replacement and what should you check?
Replace: Testosterone
Check: Symptom improvement, serum testosterone
If you are deficient in GH what is used as a replacement and what should you check?
Replace: Growth hormone
Check: IGF-1, growth chart (children)
What is the result of growth hormone deficiency in children?
Results in short stature
2SD < mean height for children that age and sex
What are the causes of short stature? (7)
1) Genetic Down's syndrome, Turner's syndrome, Prader-Willi syndrome 2) Emotional deprivation 3) Systemic disease Cystic fibrosis, Rheumatoid arthritis 4) Malnutrition 5) Malabsorption Coeliac disease 6) Endocrine disorders Cushing's syndrome, hypothyroidism, GH deficiency, poorly controlled T1DM 7) Skeletal dysplasias Achondroplasia, osteogenesis imperfecta
What hormone inhibits the release of growth hormone?
Somatostatin
What mutation causes achondroplasia?
Mutation in fibroblast growth factor receptor 3 (FGF3)
What is achondroplasia?
Abnormality in growth plate chondrocytes causing impaired linear growth
Causes average sized trunk with short arms and legs
What is Laron dwarfism? How can it be treated in children?
A mutation in the growth hormone receptor
IGF-1 treatment in childhood can increase height
If a child stays within their predicted height range, but falls off the curve age 11, what is a possible cause of this?
Coeliac disease
What are the possible causes of acquired growth hormone deficiency in adults?
1) Trauma
2) Pituitary tumour
3) Pituitary surgery
4) Cranial radiotherapy
What methods can be used to induce growth hormone release in a growth hormone provocation test?
1) GHRH + Arginine (in combination more effective than each alone) 2) Insulin I.V. via hypoglycaemia 3) Glucagon I.M. 4) Exercise
Measure plasma GH at specific time-points (before and after)
What is the NICE cut-off for GH secretion during insulin-induced hypoglycaemia to require GH replacement?
3μg/L
Somatotrophin is used for growth hormone therapy. How is it administered? When do you get the maximal dose? How is it metabolised and what is the duration of action?
Daily subcutaneous injection; monitor clinical response and adjust dose to IGF-1. Maximal plasma concentration in 2-6 hours.
Hepatic/renal metabolism with short (20 min) half-life
Lasts well beyond clearance. Peak IGF-1 levels at approximately 20 hours
What are the signs and symptoms of GH deficiency in adults?
Reduced lean mass, increased adiposity, increased waist:hip ratio
Reduced muscle strength and bulk = reduced exercise performance
Decreased plasma HDL-cholesterol (good) and raised LDL-cholesterol (bad
Impaired ‘psychological well being’ and reduced quality of life
What are the potential benefits of GH therapy in adults?
Improved body composition- decreased waist circumference, less visceral fat
Improved muscle strength and exercise capacity
More favourable lipid profile (higher HDL and lower LDL)
Increased bone mineral density
Improved psychological well-being and quality of life
What are the potential risks associated with GH therapy in adults?
Increased susceptibility to cancer - no data to support this currently
Expensive - NICE estimated cost of lifelong GH treatment in adult = £42k
What is released in the posterior pituitary?
Vasopressin (ADH)
Oxytocin
Where is vasopressing produced?
In the hypothalamus (released in the neurohypophysis)
What receptor does vasopressin act on?
V2 receptor
What does vasopressin cause synthesis of? Where does this product act?
Synthesis of AQP2
Inserted into the apical membrane of collecting duct cells
How is vasopressin release regulated?
Osmoreceptors in the organum vasculosum are very sensitive to small changes in the osmolarity of the blood, as this area does not have the normal BBB
What happens to the osmoreceptors when there is an increase in the extracellular sodium concentration?
Osmoreceptors shrink, which increases osmoreceptor firing, which in turn causes release of vasopressin from PVN and SON neurones
What is the normal response to water deprivation?
Increased serum osmolarity
Stimulation of osmoreceptors
Increased vasopressin release (and increased thirst)
Increased water reabsorption from renal collecting ducts
Reduced urine volume, increased urine osmolarity, reduction in serum osmolarity
What is diabetes insipidus?
Absence or lack of circulating vasopressin, or end organ resistance to vasopressin
What are the two types of diabetes insipidus?
Cranial (or Central)
Nephrogenic
What are the two types of cranial diabetes insipidus? Which one is more common?
Acquired (more common)
Congenital (rare)
What are possible causes of acquired diabetes insipidus?
1) Traumatic brain injury
2) Pituitary surgery
3) Pituitary tumours, craniopharyngioma
4) Metastasis to the pituitary gland, e.g. breast
5) Granulomatous infiltration of median eminance, e.g. TB, sarcoidosis
What are the possible causes of congenital nephrogenic diabetes insipidus? How common is it?
Rare
e.g. mutation in gene encoding V2 receptor, aquaporin 2 type water channel
What are the possible causes of acquired nephrogenic diabetes insipidus?
Drugs
e.g. lithium
What are the signs and symptoms of diabetes insipidus?
Polyuria
Hypoosmolar urine
Polydipsia
Dehydration if fluid intake not maintained- can lead to death
Possible disruption to sleep with associated problems
What is the mechanism of diabetes insipidus?
1) Inadequate production of/response to VP
2) Large volumes of dilute (hypotonic) urine
3) Increase in plasma osmolarity (and sodium)
4) Reduction in extracellular fluid volume
5) Thirst- polydipsia
6) Extracellular fluid volume expansion
What is psychogenic polydipsia?
Most frequently seen in psychiatric patients. Patients told to drink plenty by healthcare professionals
Excess fluid intake and excess urine output- but with ability to secrete vasopressin in response to osmotic stimuli is preserved
What is the mechanism of psychogenic polydipsia?
1) Polydipsia
2) Expansion of extracellular fluid volume, reduction in plasma osmolarity
3) Less VP secreted by neurohypophysis
4) Large volumes of dilute (hypotonic) urine
5) Extracellular fluid volume returns to normal
What is the normal (hydrated) range for plasma osmolarity?
280-295mOsm/kg H₂O
What is the plasma osmolarity of someone with diabetes insipidus usually over?
290mOsm/kg H₂O
What is the urine osmolarity of someone with psychogenic polydipsia usually under?
270mOsm/kg H₂O
What is involved in a water deprivation test?
Subject deprived of water
Healthy individuals and those with psychogenic polydipsia will start to produce concentrated urine in response. Diabetes insipidus will continue to produce dilute urine
Then administer DDAVP
Cranial DI will start to produce more concentrated urine
Nephrogenic DI will still produce dilute urine
What are the biochemical features of diabetes insipidus? (4)
1) Hypernatraemia
2) Raised urea
3) Increased plasma osmolarity
4) Dilute (hypoosmolar) urine- i.e. low urine osmolarity
What are the biochemical features of psychogenic polydipsia?
1) Mild hyponatraemia (due to excess water intake)
2) Low plasma osmolarity
3) Dilute (hypo-osmolar) urine
Where are V1 receptors located? (6)
1) Vascular smooth muscle
2) Non-vascular smooth muscle
3) Anterior pituitary
4) Liver
5) Platelets
6) CNS
Where are V2 receptors located? (2)
1) Kidney
2) Endothelial cells
What selective vasopressin V2 receptor peptidergic agonist is used in diabetes insipidus?
Desmopressin (DDAVP)
How is desmopressin administered? What must patients starting this drug ensure?
Administered - Nasal spray (normally) - Orally - Subcutaneous injection Patients must not continue to drink large amount of fluid- risk of hyponatraemia
What drug is used to treat nephrogenic diabetes insipidus?
Thiazides
e.g. bendroflumethiazide
What is the possible mechanism of thiazides?
1) Inhibits Na⁺/Cl⁻ transport in distal convoluted tubule (diuretic effect)
2) Volume depletion
3) Compensatory increase in Na⁺ reabsorption from the proximal tubule (plus small decrease in GFR etc)
4) Increased proximal water reabsorption
5) Decreased fluid reaches collecting duct
6) Reduced urine volume
What is SIADH?
Syndrome of inappropriate ADH
The plasma vasopressin concentration is inappropriately high for the existing plasma osmolarity
What is the mechanism for SIADH?
1) Increased vasopressin
2) Increased H₂O reabsorption from renal collecting ducts
3) Expansion of ECF volume [= 6) Hyponatraemia]
4) Atrial natruiretic peptide (ANP) from right atrium
5) Natriuresis
6) Hyponatraemia and euvolaemia
What are the signs or SIADH?
Raised urine osmolarity, decreased urine volume (initially)
Decreases p[NA⁺] (hyponatraemia) mainly due to increased water reabsorption
What are the symptoms of SIADH?
Can be symptomless
If p[Na⁺] <120mM: Generalised weakness, poor mental function, nausea
If p[Na⁺] <110mM: Confusion leading to coma and ultimately death
What are the possible causes of SIADH? (5)
1) CNS Subarachnoid haemorrhage, stroke, tumour, traumatic brain injury 2) Pulmonary disease Pneumonia, bronchiectasis 3) Malignancy Lung (small cell) 4) Drug-related Carbamazepine, SSRIs (selective serotonin reuptake inhibitors) 5) Idiopathic
What treatment is used for SIADH?
Appropriate treatment (e.g. surgery for tumour)
To reduce immediate concern (i.e. hyponatraemia)
1) Immediate: fluid restriction
2) Longer-term: use drugs which prevent vasopressin action in kidneys
e.g. Induce nephrogenic DI- demeclocyline; inhibit action of ADH- V2 receptor antagonists
What are Vaptans? How do they work?
Non-competitive V2 receptor antagonists
Inhibit AQP2 synthesis and transport to apical membrane, preventing renal water reabsorption
Aquaresis- solute-sparing renal excretion of water
Licensed in the UK for treatment of hyponatraemia associated with SIADH
Very expensive- limits their current use
What is the normal fasting glucose level?
4-6mmol/L
What is the diabetic blood glucose level over?
7mmol/L
What is the term for an individual with a fasting glucose level of 6-7mmol/L?
Impaired fasting glucose
What is the normal oral glucose tolerance test result after 120 mins?
7.8mmol/L
What is a diabetic oral glucose tolerance test result over after 120 mins?
11.1mmol/L
Why can’t you measure GH? What is measured instead?
GH is released in pulses ∼6 times per day.
Measure IGF-1 instead
Why must you perform a water deprivation test rather than measuring ADH levels?
ADH breaks down quickly so it cannot be measured accurately
Where is the grey and white matter located in the spinal cord?
Grey matter is in the middle surrounded by white matter
What is contained in the grey matter?
Cell bodies of interneurones and motor neurones
Neuroglia and unmyelinated axons
How is the grey matter arranged? What is the function of each section?
Arranged into dorsal and ventral horns
Dorsal horn receive sensory information from the body via spinal nerves and dorsal roots. This information produces reflex actions or is projected to the brain for processing
Ventral horns contain motor neurones whose axons control muscles of the body.
In the thoracic and upper lumbar region the intermediate horns contain sympathetic preganglionic motor neurones whose axons control visceral functions via the ventral roots and spinal nerves
What does the white matter contain?
Short pathways which interconnect adjacent segments of the spinal cord and longer tracts which convey information from the brain
It is mostly myelinated motor and sensory axons
Is damage to grey or white matter likely to result in more serious consequences?
White matter
How is the lower end of the spinal cord anchored to the coccygeal vertebrae?
The filum terminale (a pial thread)
What consequences result from sacral spine damage?
Loss of bladder and bowel function, spina bifida, neural tube defect
What consequences result from thoracic spine damage?
Loss of lower limb function and incontinence (paraplegia)
What consequences result from cervical spine damage?
Loss of lower limb and upper limb function, incontinence (quadriplegia)
High spinal legion (C1/2) cannot breathe unassisted, as the phrenic nucleus controls the diaphragm which is innervated by C3/4/5
What are the three layers of meninges which cover in the spinal cord? (from outside inwards)
Tough outer dura mater
Arachnoid mater
Delicate pia mater (continuous with the spinal cord)
What is found in the extradural space surrounding the spinal cord?
Fat and a vanour plexus
What is the name for the lateral projections which extend form the pia mater into the dura mater to help stabilise the spinal cord?
Denticulate ligaments
What direction are the tracts found in the dorsal columns in the spinal cord?
Ascending tracts (carrying sensory information)
What somatosensory information is found in the dorsal columns pathway?
Touch, proprioception and vibration
What somatosensory information is found in the spinothalamic pathway?
Pain and temperature
In the dorsal columns pathway if the primary axon enters below spinal level T6 where will it travel? And above?
Below: Fasciculus gracilis
Above: Fasciculus cuneatus
In the dorsal columns pathway where do the secondary fibres cross over?
In the sensory decussation
In the dorsal columns pathway where do secondary axons terminate?
In the ventral posterolateral nucleus (VPL) of the thalamus where they synapse with tertiary neurons
Where do the tertiary neurones of the dorsal columns pathway ascend? Where do they end?
Ascends via the posterior limb of the internal capsule
End in the primary sensory cortex
Where do the primary neurons of the spinothalamic pathway synpase?
In the substantia gelatinosa
What is Lissauer’s tract?
The tract where primary neurones of the spinothalamic pathway ascend before synapsing
Where do the tertiary neurones of the spinothalamic pathway ascend and where do they travel to?
Ascend via the posterior limb of the internal capsule to the primary sensory cortex
Which tract is motor organisation in?
The corticospinal tract
What is the route of the corticospinal tract?
Cortical upper motor neurones descend in the posterior limb of the internal capsule through the crus cerebri, down through the pons and to the medullary pyramids where 95% of the axons cross over at pyramidal decussations.
They then descend as the lateral corticospinal tract
Which spinal tract would result in contralateral loss of sensory information with a mid-thoracic spinal lesion?
Spinothalamic pathway
Which spinal tract would result in ipsilateral loss of sensory information with a mid-thoracic spinal lesion?
Dorsal columns pathway
Which spinal tract would result in ipsilateral deficits with a mid-thoracic spinal lesion?
The corticospinal tract
What determines the degree of deficit following a spinal cord lesion? (3)
1) Loss of neural tissue
2) Vertibral level
The higher the level the more severe the disability
3) Transverse plane
Which and how many tracts are affected
What is hyperreflexia?
Overactive or over responsive reflexes resultant from injury at T5 level and above
What is syringomyelia?
Disorder in which a cyst or cavity forms within the spinal cord. Usually seen in the cervical region, so upper limbs are affected
What is a spinal glioma?
A tumour within the spinal cord
What are the usual causes of hyperpituitarism? What symptoms are associated with this?
Usually due to isolated pituitary tumours but can also be ectopic in origin
Can be associated with visual field and other (e.g. cranial nerve) defects as well as endocrine-related signs and symptoms
What is bitemporal hemianopia? Why does this occur?
A loss of part of the field of vision.
When a suprasellar tumour in the pituitary compresses the optic chiasm so only the fibres which don’t cross over here will provide sensory information
What disorder results from hyperpituitarism where there is excess ACTH?
Cushing’s disease
What disorder results from hyperpituitarism where there is excess TSH?
Thyrotoxicosis
What disorder results from hyperpituitarism where there are excess gonadotrophins?
Precocious puberty in children
What disorder results from hyperpituitarism where there is excess prolactin?
Hyperprolactinaemia
What disorder results from hyperpituitarism where there is excess growth hormone?
Gigantism or Acromegaly
What is the most common functioning pituitary tumour? What does this suppress?
Prolactinoma
Suppresses GnRH pulsatility
What is the pathological cause of hyperprolactinaemia?
Prolactinoma
Often microadenomas <10mm in diameter
What are the physiological causes of hyperprolactinaemia?
Pregnancy or breastfeeding
What are the symptoms of hyperprolactinaemia due to pituitary adenoma in women?
Galactorrhoea (milk production)
Secondary amenorrhoea (or oligomenorrhoea)
Loss of libido
Infertility
What are the symptoms of hyperprolactinaemia due to pituitary adenoma in men?
Galactorrhoea uncommon (since appropriate steroid background is usually inadequate) Loss of libido Erectile dysfunction Infertility
What cell is prolactin secreted from? How is prolactin secretion switched off?
Secreted from lactotrophs in the adenohypophysis
Dopamine from hypothalamic dopaminergic neurones binds to D2 receptors which switches off prolactin secretion
What treatment is used for hyperprolactinaemia? Give examples.
Dopamine receptor D2 agonists decrease prolactin secretion and reduce tumour size
e.g. Cabergoline (and less frequently Bromocriptine) are given orally
What side effects are associated with dopamine receptor agonists?
Nausea and vomitting Postural hypotension Dyskinesias (movement difficulty) Depression Pathological gambling
What does excess growth hormone in childhood result in? What usually causes it?
Gigantism
Usually due to benign growth hormone secreting pituitary adenoma
What does excess growth hormone in adulthood result in? What usually causes it?
Acromegaly
What are the causes of death in Acromegaly?
Cardiovascular disease: 60%
Respiratory complications: 25%
Cancer: 15%
What grows in Acromegaly?
Periosteal bone Cartilage Fibrous tissue Connective tissue Internal organs (cardiomegaly, splenomegaly, hepatomegaly, etc)
What are the clinical features of Acromegaly? (8)
- Excessive sweating (hyperhidrosis)
- Headache
- Enlargement of supraorbital ridges, nose, hands and feet, thickening of lips and general coarseness of features
- Macroglossia
- Mandible grows causing protrusion of lower jaw (prognathism)
- Carpal tunnel syndrome (median nerve compression)
- Barrel chest, kyphosis
- Spade-shaped hands with doughy palms
What are the metabolic effects of Acromegaly?
1) Excess growth hormone (GH)
2) Excess GH inhibits insulin signalling
3) Increased insulin resistance
4) Impaired glucose tolerance
5) Diabetes mellitus
What complications are associated with Acromegaly?
1) Obstructive sleep apnea
2) Hypertension
3) Cardiomyopathy
4) Increased risk of cancer
Why is obstructive sleep apnea associated with Acromegaly?
Bone and soft tissue changes surrounding the upper airway lead to narrowing and subsequent collapse during sleep
Why is hypertension associated with Acromegaly?
Direct effects of GH and/or IGF-1 on the vascular tree
GH-mediated renal sodium reabsorption
Why is cardiomyopathy associated with Acromegaly?
Hypertension, diabetes mellitus, direct toxic effects of excess GH on myocardium
Why is an increased risk of cancer associated with Acromegaly?
Colonic polyps
Regular screening with colonoscopy
What co-secretion is often associated with acromegaly? What does this cause?
Prolactin is often high in acromegaly- may reflect a tumour secreting GH and prolactin
Hyperprolactinaemia will cause secondary hypogonadism
What hormone inhibits GH release from the adenohypophysis?
Somatostatin
What effect does growth hormone have on the liver?
Induces release of somatomedins (mainly IGF-1)
How is acromegaly diagnosed?
GH is pulsatile so random measurement is unhelpful
Instead, measure IGF-1 (will be elevated in Acromegaly)
Failed suppression of GH following oral glucose load (perform oral glucose tolerance test)
What are the treatment options for Acromegaly?
1) Surgery (trans-sphenoidal)
- 1st Line
2) Medical
- Somatostatin analogues
- Dopamine agonists
3) Radiotherapy
Give an example of a somatostatin analogue used in the treatment of Acromegaly. Describe the use of these drugs and their side effects?
Octreotide
Injection: Subcutaneous (short-acting) or monthly depot
Side effects: Nausea, diarrhoea, gallstones (GI)
Reduces GH secretion and tumour size
Pretreatment before surgery may make resection easier
Used post-op if not cured or whilst waiting for radiotherapy
Give an example of a dopamine agonist used in the treatment of Acromegaly.
Cabergoline
What is thyroxine?
Prohormone T4
Converted into the active metabolite T3
What drug is used in thyroid hormone replacement therapy?
1) Levothyroxine sodium (T4)
Usually the drug of choice
2) Liothyronine sodium (T3)
Less commonly used
What is the clinical use of Levothyroxine sodium in primary hypothyroidism? How is it administered and how is the correct dose given?
1) Autoimmune primary hypothyroidism
2) Iatrogenic primary hypothyroidism (e.g. post-thyroidectomy, post-radioactive iodine)
Oral administration
TSH used as a guide for thyroxine dose- suppress TSH into reference range
What is the clinical use of Levothyroxine sodium in secondary hypothyroidism? How is it administered and how is the correct dose given?
e.g. pituitary tumour, post-pituitary surgery or radiotherapy
Oral administration
TSH low due to anterior pituitary failure, so can’t use TSH as a guide to dose. Instead aim for fT4 in the middle of the reference range
What is the clinical use of Liothyronine? How is it administered?
Myxoedema coma- a very rare complication of hypothyroidism
IV administration
Onset of action faster than T4 (then oral when possible)
What symptoms occur with combined thyroid hormone replacement?
Combination T3/T4- some reported improvement in well-being
Complicated by symptoms of ‘toxicity’- palpitations, tremor, anxiety- often combination treatment suppresses TSH
What are the adverse effects of thyroid hormone over-replacement?
Usually associated with low/suppressed TSH
1) Skeletal- increased bone turnover, reduction in bone mineral density, risk of osteoporosis
2) Cardiac- tachycardia, risk of dysrhythmia, particularly atrial fibrillation
3) Metabolism- increased energy expenditure, weight loss
4) Increased β-adrengergic sensitivity- tremor, nervousness
What is the half-life of Levothyroxine?
6 days
What is the half-life of Liothyroxine
2.5 days
What percentage of circulating T4 and T3 are bound to plasma proteins? Which plasma protein mainly binds to these?
Thyroxine binding globulin
∼99.97% of T4
∼99.7% of circulating T3
What conditions increase the amount of plasma binding proteins?
Pregnancy
Patients on prolonged treatment with oestrogens and phenothiazines
What conditions decrease the amount of plasma binding proteins?
Malnutrition
Liver disease
Certain drug treatments
Give examples of co-administered drugs that compete for protein binding sites.
Phenytoin
Salicylates
How much more T4 is in the plasma compared with T3?
10 times
How is free and conjugated T3 and T4 secreted? How long does it take to be cleared?
Secreted in the bile and urine
T3 is cleared in hours
T4 takes 6 days
What are the different classes of drugs used in the treatment of hyperthyroidism?
1) The thionamides (anti-thyroid drugs)
- propylthiouracil (PTU)
- carbimazole (CBZ)
2) Potassium iodide
3) Radioiodine
4) β-blockers
- help with symptoms, don’t help with thyroid hormone function
What are the uses of thionamides?
1) Daily treatments of hyperthyroid conditions
2) Treatment prior to surgery
3) Reduction of symptoms while waiting for radioactive iodine to act
What is the mechanism of action of thionamides?
1) They inhibit thyroperoxidase and peroxidase transaminase which inhibits T3/4 synthesis and secretion
2) May also suppress antibody production in Graves’ disease
3) Reduces conversion of T4 to T3 in peripheral tissue (PTU)
What are the unwanted actions of thionamides?
1) Agranulocytosis/granulocytopenia (reduction or absence of granular leukocytes)- rare and reversible on withdrawal of the drug
2) Rashes (relatively common)- normally associated with one drug, so swapping drug type relieves this
Describe the pharmacokinetics of thionamides.
Orally active
Carbimazole is a prodrug which has to be converted to methimazole
Plasma half-life of 6-15 hours
Crosses placenta and is secreted in breastmilk
Metabolised in the liver and secreted in the urine
Which thionamide crosses the placenta and is secreted in breastmilk less?
Propylthiouracil
PTU
How long is anti-thyroid drug treatment used before it is aimed to stop?
18 months
Why would β-blockers be used in thyrotoxicosis?
Thionamides take several weeks to have clinical effects e.g. reduce tremor, slow heart rate, less anxiety etc
β-blockers (e.g. propranolol) will achieve these effects in the interim
When is potassium iodide used?
1) Preparation of hyperthyroid patients for surgery
2) Severe thyrotoxic crisis
What is the mechanism of action of potassium iodide?
1) Inhibits iodination of thyroglobulin
2) Inhibits H₂O₂ generation
How long does it take for the effects of potassium iodide to be seen?
Hyperthyroid symptoms reduced withing 1-2 days
Vascularity and size of gland reduced within 10-14 days
What are the unwanted effects of potassium iodide?
Allergic reactions
e.g. rashes, fever, angiooedema
How is potassium iodide administered? When are the maximum effects seen?
Oral administration
Maximal effects seen after 10 days continuous administration
What is radioiodine used to treat?
Treats hyperthyroidism
Graves, toxic nodular disease, thyroid cancers
How does radioiodine work?
Accumulates in the colloid; emits β particles, destroying follicular cells
What are the pharmacokinetics of radioiodine?
Discontinue anti-thyroid drugs 7-10 days prior to radioiodine treatment
Administer as a single oral dose
Radioactive half-life of 8 days
Radioactivity negligible after 2 months
What risks are associated with radioiodine treatment?
Must avoid close contact with small children for several weeks after receiving radioiodine
Contra-indicated in pregnancy and breast feeding
What are the symptoms of hypothyroidism?
Hair dry and brittle
- Lethargy, memory impairment, depression
- Oedema of face and eyes
- Thick tongue, slow speech
- Deepening voice
- Cold intolerance, diminished perspiration
- Cardiomegaly, poor heart sounds, hypertension
- Weight gain with reduced appetite and ascites
- Constipation
- Eventually myxodema coma
What is bilateral exophthalmos?
Seen in Graves’ disease, where the antibodies bind to muscles in the back of the eye, causing them to swell
What are the symptoms of hyperthyroidism?
- Fatigue or muscle weakness
- Hand tremors
- Mood swings
- Nervousness or anxiety
- Rapid heartbeat
- Heart palpitations or irregular heartbeat
- Skin dryness
- Trouble sleeping
- Weight loss
- Increased frequency of bowel movements
- Light periods or skipping periods
- Exophthalmos and lid lag (corneal scarring)
What disorder is associated with excess cortisol? Give two examples of drugs used to inhibit steroid biosynthesis.
Cushing’s syndrome
- Metyrapone
- Ketoconazole
What disorder is associated with excess aldosterone? Give two examples of drugs used as an mineralocorticoid receptor antagonist.
Conn’s syndrome
- Spironolactone
- Epleronone
What is metyrapone used to treat? What is it’s action and mechanism?
Used to treat Cushing’s syndrome
- Cortisol synthesis blocked
- ACTH secretion increased
- Plasma deoxycortisol increased
Causes inhibition of 11β-hydroxylase
Steroid synthesis in the zona fasciculata (and reticularis) is arrested at the 11-deoxycortisol stage
11-deoxycortisol has no negative feedback effect on the hypothalamus and pituitary gland
When is metyrapone used?
In the control of Cushing’s syndrome prior to surgery
- to get serum cortisol between (150-300nmol/L)
- improves patient’s symptoms and promotes better post-op recovery
Used to control Cushing’s symptoms after radiotherapy
What are the side effects of metyrapone?
Hypertension on long administration
- deoxycorticosterone accumulates in the zona glomerulosa and has aldosterone-like activity, leading to salt retention
Hirsutism
(excessive hair growth)
What is ketoconazole used to treat? What is it’s action and mechanism?
Used to treat Cushing’s syndrome
Main use as an antifungal agent (withdrawn in 2013 due to hepatotoxicity)
At higher concentrations, inhibits steroidogenesis - off label use
- Blocks action of glucocorticoids, mineralocorticoids and sex steroids
What are the side effects of ketoconazole?
Liver damage- possibly fatal
Monitor liver function weekly, clinically and biochemically
What is spironolactone used to treat? What is it’s action and mechanism?
Primary hyperaldosteronism (Conn's syndrome) It is converted to several active metabolites, including canrenone, a competitive antagonist of the mineralocorticoid receptor Blocks Na⁺ reabsorption and K⁺ excretion in the kidney tubules (K⁺ sparing diuretic)
Where is spironolactone metabolised?
In the liver
What are the side effects of spironolactone?
Menstrual irregularities (+ progesterone receptor) Gynaecomastia (- androgen receptor)
What is epleronone used to treat?
Conn’s syndrome (a mineralocorticoid receptor antagonist
Why is epleronone preferable to spironolactone?
Similar affinity to the mineralocorticoid receptor compared to spironolactone
Less binding to androgen and progesterone receptors compared to spironolactone, so better tolerated
What are the symptoms of Cushing’s syndrome?
Too much cortisol
- Centripetal obesity
- Moon face
- Osteoporosis
- Diabetes
What are the possible causes of Cushing’s syndrome?
1) Taking too many steroids
2) A pituitary tumour
3) Ectopic tumour secreting ACTH
4) Adrenal adenoma
How does a dexamethasone suppression test diagnose Cushing’s syndrome?
Dexamethasone is an artificial steroid
Low dose- it is administered every 6 hours for 48 hours in a 0.5mg dose
-Normal patients will respond by suppressing their cortisol levels to zero but Cushing’s patients will fail to suppress their cortisol levels.
High dose determines the type of pituitary Cushing’s disease
- Only pituitary Cushing’s will suppress their cortisol to 50%; ectopic ACTH and adrenal tumours will not suppress at all
What is Conn’s syndrome?
A benign adrenal cortical tumour in the zona glomerulosa, which causes excessive aldosterone release, leading to hypertension and hypokalaemia
What are the possible causes of adrenocortical failure?
1) Adrenal glands destroyed
- Tuberculous Addison’s disease
- Autoimmune Addison’s disease
2) Congenital adrenal hyperplasia
What are the consequences of adrenocortical failure?
- Fall in blood pressure
- Loss of salt in the urine
- Increased plasma potassium
- Fall in glucose due to glucocorticoid deficiency
- High ACTH resulting in increased pigmentation
- eventual death due to severe hypotension
Why do you get skin pigmentation in Addison’s disease?
As cortisol is not being produced ACTH is increased.
ACTH is produced from a large precursor molecule POMC. POMC is cleaved into ACTH and MSH
MSH = Melanocyte-stimulating hormone which causes increased skin pigmentation
How do you test for Addison’s disease?
FBC = ↑↑↑ K⁺, ↓Na⁺
Meausre cortisol at 9am = low
ACTH = high
Cortisol at time 0 (270-900)
Short synATCHen test (I.M. injection)
Measure cortisol at time 30 and 60 (>600)
In Addison’s flattened response to ACTH
What is the most common cause of Congenital Adrenal Hyperplasia?
21-hydroxylase deficiency
What are the different types of Congenital Adrenal Hyperplasia? What is it?
Complete or Partial
Large adrenal glands with poor function. Inability to synthesise one hormone
What results from Congenital Adrenal Hyperplasia with 21-hydroxylase deficiency?
Deficiency in aldosterone and cortisol
BUT not sex steroids
Causes sex steroids to be made in excess due to increased precursors that get converted into sex steroids (↑ ACTH)
Excess testosterone
What age will someone present with Congenital Adrenal Hyperplasia with 21-hydroxylase deficiency?
Usually by 1 week old
Before birth foetus gets steroids across the placenta
Girls might have ambiguous genitalia
How will a patient present with partial Congenital Adrenal Hyperplasia with 21-hydroxylase deficiency? What are the main problems?
Can make enough aldosterone and cortisol to survive, but they are deficient
Produce excess sex steroids and testosterone
Can present at any age
In girls: Hirsuitism and virilisation
In boys: Precocious puberty
What results from Congenital Adrenal Hyperplasia with 11β-hydroxylase deficiency?
Patient will produce lots of 11-deoxycorticosterone which is a mineralocorticoid and behaves like aldosterone.
It is produced in excess as it does not provide negative feedback so produces hypertension (excess water retention) and hypokalaemia (excess excretion)
Deficient in cortisol and aldosterone
Excess 11-deoxycorticosteron, sex steroids and testosterone
Problems with virilisation
What results from Congenital Adrenal Hyperplasia with 17-hydroxylase deficiency?
Deficient in cortisol and sex steroids
Excess 11-deoxycorticosterone and aldosterone
Problems with hypertension, low K⁺, sex steroid deficiency and glucocorticoid deficiency (low glucose)
What stimulates the hypothalamus to release corticotrophin-releasing hormone?
Circadian rhythm
Stress
What regulates the release of aldosterone?
The Renin-Angiotensin system
In adrenocortical failure what hormones need to be replaced?
Cortisol and aldosterone must be replaced
Androgens do not need to be replaced as the gonads are the main source and they can take over sufficiently
What hormone binds to the glucocorticoid receptor?
Cortisol
What hormone binds to the mineralocorticoid receptor?
Aldosterone and cortisol
Cortisol has higher affinity
Where are glucocorticoid receptors located?
Wide distribution in the body
Where are mineralocorticoid receptors located?
In the kidney
discrete distribution
How is cortisol prevented from binding to aldosterone receptors?
11β-hydroxysteroid dehydrogenase 2 converts cortisol to cortisone which is inactive
Why do patients with Cushing’s syndrome have hypertension and hyperkalaemia?
High cortisol, eventually 11β-HSD becomes saturated and can’t convert any more cholesterol so the cholesterol binds to the mineralocorticoid receptors
= ↑ Na⁺ resorption, ↑ water resorption, ↑ K⁺ excretion
= hypertension, hypokalaemia
What is the receptor selectivity of hydrocortisone?
Glucocorticoid with mineralocorticoid activity at high doses
What is the receptor selectivity of prednisolone?
Glucocorticoid with weak mineralocortiocid activity
What is the receptor selectivity of dexamethasone?
Synthetic glucocorticoid with no mineralocorticoid activity
What is the receptor selectivity of fludrocortisone?
Aldosterone analogue
Used as an aldosterone substitute
What are the routes of administration of corticosteroids?
Oral - Hydrocortisone - Prednisolone - Dexamethasone - Fludrocortisone Parenteral (I.V. or I.M.) - Hydrocortisone - Dexamethasone
What plasma proteins bind corticosteroids?
Cortisol Binding Globulin
Albumins
What is the duration of action of hydrocortisone?
∼8 hours
What is the duration of action of prednisolone?
∼12 hours
What is the duration of action of dexamethasone?
∼40 hours
What drugs are used to treat Addison’s disease?
Patients lack cortisol and aldosterone
Treat with hydrocortisone (replaces cortisol) and fludrocortisone (replaces aldosterone) by mouth
What drugs are used to treat patients with ACTH deficiency
Patients lack cortisol but aldosterone is normal (RAAS)
Treat with hydrocortisone
What is the treatment for Addisonian crisis?
First therapeutic step- I.V. saline (0.9% sodium chloride) to rehydrate patient
High dose hydrocortisone
- I.V. infusion or I.M. every 6 hours
- Has mineralocorticoid effect at high dose (11β-HSD overwhelmed) so no need to replace aldosterone
5% dextrose if hypoglycaemic
What are the objectives of therapy in a patient with Congenital Adrenal Hyperplasia?
- Replace cortisol
- Suppress ACTH and thus, adrenal androgen production
- Replace aldosterone in salt wasting forms
What is the therapy used for Congenital Adrenal Hyperplasia? How is therapy monitored? What are the side effects?
Given cortisol replacement at very high doses compared to Addison’s to reduce ACTH
Measure 17 OH progesterone (high ACTH = high 17 OH prog)
Cushingoid - Glucocorticoid dose is too high
Hirsuitism - Glucocorticoid dose is too low
When do patient’s with glucocorticoid replacement need to increase their dose?
In minor illness double the dose
During surgery- hydrocortisone I.M. with pre-med and at 6-8 hour intervals. oral once eating and drinking
What hormone suppresses GnRH to prevent the release of testosterone?
Inhibin
How long is a menstrual cycle? What are the phases of the cycle?
28 days
- Follicular phase
- Ovulation
- Luteal phase
What happens in the follicular phase of the menstrual cycle?
Low level of LH and FSH stimulate development of follicles. These develop and start to produce oestradiol, progesterone and inhibin. Inhibin gives negative feedback to the hypothalamus
What hormones spike in ovulation?
Oestradiol
Progesterone
What occurs in the luteal phase of the menstrual cycle?
If implantation does not occur the endometrium is shed
If implantation does occur = pregnancy
Luteal phase is the release of an egg and the subsequent hormonal change. Large progesterone spike (plus oestradiol and inhibin) peaking at the middle of the Luteal phase. As progesterone release decreases it initiates menstration
What is infertility?
The inability to conceive after 1 year of regular unprotected sex
What hormone levels would be found in a patient with primary gonadal failure?
High GnRH
High LH
High FSH
Low testosterone/oestradiol
What hormone levels would be found in a patient with hypopituitary disease?
Low LH
Low FSH
Low testosterone/oestradiol
What are the clinical features of male hypogonadism?
Loss of libido Impotence Small testes Decrease muscle bulk Osteoporosis
What are the causes of male hypogonadism? (4)
1) Hypothalamic-pituitary disease
- Hypopituitarism
- Kallman’s syndrome (anosmia + low GnRH)
- Illness/underweight
2) Primary gonadal disease
- Congenital: Klinefelter’s syndrome (XXY)
- Acquired: Testicular torsion, Chemotherapy
3) Hyperprolactinaemia
4) Androgen receptor deficiency
What investigations are conducted if male hypogonadism is suspected?
1) LH, FSH, testosterone
- if all low MRI pituitary
2) Prolactin
3) Sperm count
- Azoospermia = absence of sperm in ejaculate
- Oligospermia = reduced numbers of sperm in ejaculate
4) Chromosomal analysis (Klinefelter’s XXY)
What is the treatment for male hypogonadism?
Replacement testosterone for all patients
For fertility: if hypo/pit disease
- subcutaneous gonadotrophins
Hyperprolactinaemia- dopamine agonist
What are the endogenous sites of androgen production?
1) Interstitial Leydig cells of the testes
2) Adrenal cortex (males and females)
3) Ovaries
4) Placenta
5) Tumours
What are the main actions of testosterone?
1) Development of the male genital tract
2) Maintains fertility in adulthood
3) Control of secondary sexual characteristics
4) Anabolic effects (muscle, bone)
How much of circulating testosterone is protein bound?
98%
What are the products of tissue-specific processing of testosterone? What receptor do these products act on?
1) Dihydrotestosterone (DHT)
acts via the androgen receptor
2) 17β-oestradiol
acts via the oestrogen receptor
What are the different types of amenorrhoea?
1) Primary amenorrhoea
failure to begin spontaneous menstruation by age 16 years
2) Secondary amenorrhoea
absence of menstruation for 3 months in a woman who has previously had cycles
3) Oligomenorrhoea
irregular long cycles
What are the possible causes of amenorrhoea?
1) Pregnancy / lactation
2) Ovarian failure
- premature ovarian failure
- ovariectomy / chemotherapy
- ovarian dysgenesis (Turner’s 45 X)
3) Gonadotrophin failure
- Hypo / pit disease
- Kallmann’s syndrome (anosmia, low GnRH)
- Low BMI
- Post pill amenorrhoea
4) Hyperprolactinaemia
5) Androgen excess: gonadal tumour
What investigations are conducted in a patient with amenorrhoea?
Pregnancy test LH, FSH, oestradiol Day 21 progesterone Prolactin, thyroid function tests Androgens (testosterone, androstenedione, DHEAS) Chromosomal analysis (Turner's 45 X) Ultrasound scan ovaries / uterus
What is the treatment for amenorrhoea?
1) Treat the cause (e.g. low weight)
2) Primary ovarian failure - infertile, HRT
3) Hypothalamic / pituitary disease
- HRT for oestrogen replacement
- Fertility: gonadotrophins (LH and FSH) - part of IVF treatment
What diseases have an increased risk in polycystic ovarian syndrome?
Increased cardiovascular risk
Increased insulin resistance ( >diabetes)
What is the criteria to diagnose PCOS?
Need 2 of the following:
- polycystic ovaries on ultrasound scan
- oligo- / anovulation
- clinical / biochemical androgen excess
What are the clinical features of PCOS?
1) Hirsuitism
2) Menstrual cycle disturbance
3) Increased BMI
What is the treatment for PCOS with regard to fertility?
Metformin
Clomiphene
Gonadotrophin therapy as part of IVF treatment
What is the mechanism of clomiphene?
An anti-oestrogenic in the hypothalamo-pituitary axis
Binds to oestrogen receptors in the hypothalamus thereby blocking the normal negative feedback, resulting in an increase in the secretion of GnRH and gonadotrophins
How is prolactin secretion controlled?
Thyrotrophin-releasing hormone stimulates the pituitary to release prolactin
Dopamine inhibits the release of prolactin
Prolactin has negative feedback on the hypothalamus (inhibits GnRH pulsatility) and on LH actions on ovary / testes
What are the causes of hyperprolactinaemia?
1) Dopamine antagonist drugs
- Anti-emetics (metoclopramide)
- Anti-psychotics (phenothiazines)
2) Prolactinoma
3) Stalk compression due to pituitary adenoma
4) PCOS
5) Hypothyroidism
6) Oestrogens (OCP), pregnancy, lactation
7) Idiopathic
What are the clinical features of hyperprolactinaemia?
Galactorrhoea Reduced GnRH secretion / LH action - hypogonadism Prolactinoma - headache - visual field defect
What is the treatment of hyperprolactinaemia?
1) Treat the cause - stop drugs
2) Dopamine agonist
- Bromocriptine
- Cabergoline
3) Prolactinoma
- Dopamine agonist therapy
- Pituitary surgery rarely needed
A male presents to endocrine clinic who has had bilateral orchidectomy. What would you expect his blood results to show?
Low testosterone
High LH
High FSH
A young woman presents to endocrine clinic who complains of secondary amenorrhoea and galactorrhoea. Her GP measured her prolactin at 4500 (high). What would you expect her blood results to show?
Low LH
Low FSH
Low oestradiol
What is the mechanism of cabergoline? How is it used to treat a prolactinoma?
It is a dopamine agonist. It inhibits prolactin which brings down the prolactin levels and shrinks the tumour
What causes hypothalamic amenorrhoea? Why?
Over-exercising
Severe weight loss
Anorexia
Less fat = less leptin. Leptin produced from adipose tissue linked to amenorrhoea
If you are prescribed cabergoline to treat a prolactinoma when would it be necessary to continue treatment prior to conceiving and when would it be possible to stop taking it? Can you stop taking it indefinitely?
Depends on the size of the prolactinoma
If it is a macroprolactinoma that is touching the optic chiasm then continue cabergoline
If it is a microprolactinoma stop taking cabergoline and monitor headaches and visual field every trimester
How does cabergoline affect a woman who wants to breastfeed? How is cabergoline managed in a woman who wants to breastfeed?
If you are taking cabergoline you cannot breastfeed.
Take cabergoline until 34 weeks then monitor the visual field and headaches to see if the prolactinoma is growing or compressing the optic chiasm
What investigations would be performed on a woman of 30 who has not had a period for 3 months and has a BMI of 18?
Pregnancy test
Blood test (prolactin, LH, FSH, oestrogen, hyper/hypothyroid, androgens- PCOS)
High prolactin- pituitary MRI
Low oestrogen, high LH and FSH = something wrong with ovaries
If a woman presents with the following results what is the interpretation?
High oestrogen
Low LH
Low FSH
Pregnancy
If a woman presents with the following results what is the interpretation?
Low oestrogen
Low LH
Low FSH
High prolactin
Prolactinoma / pituitary tumour
If a woman presents with the following results what is the interpretation?
Low oestrogen
High LH
High FSH
Damage to the gonads
Why must oestradiol be given in higher doses if administered orally? How can this be avoided?
It undergoes extensive first pass metabolism
Can be avoided by administering it intramuscularly or as a transdermal patch
How much of circulating oestrogen is plasma protein bound? What proteins bind oestrogen?
70%
Sex hormone binding globulin or albumin
What are the different types of contraceptive?
1) Combined oral contraceptives
2) Progesterone only contraceptive
3) “Emergency” contraceptive
How does a combined oral contraceptive work to prevent pregnancy?
- Feedback actions of progesterone in the hypothalamus and pituitary
- Progesterone thickens cervical mucus which provides hostile environment to sperm
- Oestrogen up-regulates progesterone receptors, enhancing sensitivity to progesterone
- Oestrogen counteracts the androgenic effects of synthetic progesterone, preventing masculinisation
- Oestrogen contributes to negative feedback at hypothalamus and pituitary, by synergising with progesterone
What are the different types of combined oral contraceptive?
Monophasic: one concentration taken throughout
Triphasic: 3 step-wise changes in oestrogen/progesterone ratio
What are the side effects of oestrogen?
Increased clotting factors (increased thromboembolic disease)
Increased proliferation of endometrium (increased risk of cancer)
Breast discomfort
Increased water and salt retention may cause oedema, increased hypertension)
Nausea (triggering vomiting centre of the brain)
Headaches
Increased weight gain (fat deposition and oedema)
What is the effectiveness of the emergency contraception?
75-85%
What is menopause?
Permanent cessation of menstruation resulting from the loss of ovarian follicular activity and 12 months of amenorrhoea at the time of midlife (arounf 50, range 45-55)
What are the symptoms of menopause?
- Irregular cycles and hot flushes (inc. at night- insomnia)
- Psychosocial symptoms (e.g. depression, mood swings, loss of energy)
- Translucent thin skin
- Decreased libido
- Urogenital atrophy
What complications are associated with menopause?
Osteoporosis: oestrogen deficiency- loss of bone matrix, decrease in bone mass and increased fracture risk
Cardiovascular disease: women are protected against CVD before menopause, but have the same risk as men by 70 years
What are the different types of HRT? When are they used? Give an example of each drug.
Oestrogen-only: Used for women who have had a hysterectomy.
e.g. Premarin
Combined: Used to prevent endometrial hyperplasia in all other women.
e.g. PremPro, CEEs and medroxyprogesterone
What hormone controls tubular fluid reabsorption?
Oestrogen
What hormone controls nutrients and glycoprotein secretion into epididymal fluid?
Androgens
What enzyme converts androgens to oestrogens?
Aromatase
What does the semen contain? How many spermatozoa in the semen?
Semen:
- Spermatozoa (15-120 x 10⁶/ml)
- Seminal fluid (2-5ml)
- Leucocytes
- Potentially viruses (e.g. hepatitis B, HIV)
What percentage of spermatozoa in the ejaculate enter the cervix?
1%
Where is seminal fluid produced?
Small contribution from - Epididymis/testis Mainly from accessory sex glands - Seminal vesicle - Prostate - also bulbourethral glands
What is capacitation of the sperm? What is the process?
Maturation of the sperm so it can achieve fertilising capability
- Loss of glycoprotein coat
- Change in the surface membrane characteristics
- Whiplash movements of the tail
What hormone is capacitation of sperm dependent on? Where does it occur?
Oestrogen-dependent
Takes place in ionic and proteolytic environment of the fallopian tube
Ca²⁺ dependent mechanism
What is the acrosome reaction?
1) Sperm binds to the ZP3 receptors on the glycoprotein coating of the ovum (zona pellucida)
2) This causes a Ca²⁺ influx into the sperm (stimulated by progesterone)
3) The sperm then releases hyaluronidase and proteolytic enzymes
4) Sperm then penetrates the zona pellucida
What does hyaluronidase do?
Breaks polysaccharides
What happens when fertilisation occurs? What is the process?
Triggers a cortical reaction
Cortical granules are located in the cortex (underneath the plasma membrane of the ovum) and these fuse with the membrane once a sperm has entered and release their contents into zona pellucida which causes if to degrade ZP2 and ZP3 which prevents sperm from binding
Where does fertilisation occur?
In the fallopian tube
What are polar bodies?
Produced from unequal division of the ovum; contains only genetic material, no cytoplasm
How long can a fertilised ovum survive before implantation as it travels down the fallopian tube? How does it receive nutrients?
Can last around 9-10 days
Receives nutrients from uterine secretions
How does implantation of a blastocyst occur?
Attachment phase: outer trophoblast cells contact uterine surfece epithelium
Decidualization of underlying stromal tissue (within a few hours)
What hormones are requires for implantation of a blastocyst to occur?
Requires progesterone domination in the presence of oestrogen
What hormones are secreted from the secretory glands in the endometrial lining that promotes adhesion of the blastocyst?
LIF (leukaemia inhibitory factor)
IL11
What is decidualisation? What changes occur?
Endometrial changes due to progesterone
- Glandular epithelial secretion
- Glycogen accumulation in stromal cell cytoplasm
- Growth of capillaries
- Increased vascular permeability (oedema)
What is the first hormone to peak during pregnancy (<10 weeks)
hCG
human chorionic gonadotrophin
What happens to the hormones in the first 5-6 weeks of pregnancy?
Rising circulating progesterone and oestradiol
Essential for developing fetoplacental unit
Inhibits maternal LH and FSH (-ve feedback)
Where is hCG produced?
Produced by the developing blastocyst
At what point during pregnancy does the fetoplacental unit take over oestrogen production?
From day 40
How does the placenta produce oestrogen?
The fetus and mother produce DHEAS which the placenta then converts to oestrogen
What maternal hormones increase during pregnancy?
- ACTH
- Prolactin
- Iodothyronines
- Adrenal steroids
- PTHrp (lactation)
What maternal hormones decrease during pregnancy?
- Gonadotrophins
- TSH
- hGH decreases as the placental hGH-variant increases towards term
What effect does high ACTH have during pregnancy?
Would cause high cortisol, so normal pregnant women can be diagnosed with Cushing’s
Why does prolactin increase during pregnancy? What impact does this have clinically?
High prolactin shuts off the HPG axis so you can’t become pregnant.
Clinically this means you can’t use prolactin levels to monitor a pituitary adenoma. Instead check visual field detects and headache symptoms
What happens to thyroid hormones during pregnancy?
Thyroxine production (and T3 and T4) increases driven by hCG
TSH decreases due to negative feedback
Parathyroid related hormone (PTHrp) is produced by breast tissue and is involved in lactation increases during pregnancy and can cause hypercalcaemia
What happens to gonadotrophins during pregnancy?
Levels decrease due to excess levels of oestrogen
What happens to hGH (growth hormone) during pregnancy?
Decreases as the placental hGH increases towards term
How does oxytocin cause contraction of breast tissue?
Stimulates an influx of calcium
What hormones are involved in lactation?
Suckling stimulates the hypothalamus→pituitary to produce prolactin which stimulates milk synthesis and oxytocin which causes milk ejection
If a patient has low Na⁺ and high K⁺ what does this mean?
They are dehydrated
What is congenital adrenal hyperplasia?
Where a baby does not produce cortisol and aldosterone; less negative feedback so increased ACTH which drives hyperplasia of adrenals
What is the commonest enzyme to be deficient in with congenital adrenal hyperplasia?
21 hydroxylase
Why does virilisation occur with 21 hydroxylase deficiency?
21 hydroxylase deficiency prevents production of cortisol and aldosterone from cholesterol, so all reagents get pushed into testosterone production which causes virilisation
How would you test for 21 hydroxylase insufficiency?
- Would perform a blood test for 17 hydroxyprogesterone (which is proximal to block so expect it to be high- continuing feedback and not being converted)
- High androgens and ACTH
- Low aldosterone
What treatment is used for 21 hydroxylase insufficiency?
Give hydrocortisone (or prednisolone which is longer lasting)
What steroid replacement is needed peri-operatively for pituitary tumour removal surgery?
Need to give hydrocortisone (IV or intermittent IM following natural cycle) then taper dose down gradually
- done in case natural cells are removed
Aldosterone not under control of ACTH so doesn’t need replacement
What advice is given to patients on cortisol replacement?
- Need to double dose if you get ill (cold) for two days
- If you vomit you need to inject or go to A&E- FATAL
How do you assess whether a patient needs long term steroid replacement?
Assess HPA axis when dose has been tapered down
- Insulin tolerence test (administer insulin to make them hypoglycaemic, then see if cortisol levels go up)
How much of the body’s calcium is stored in bone?
> 95%
What is the inorganic mineral component of bone? How much of bone is composed of this?
Calcium hydroxyapatite crystals fill the space between collagen fibrils
65% bone mass
What are the organic components of bone? What percentage of bone is made up of this?
Osteoid- unmineralised bone (35% bone mass)
Type 1 collagen fibres (95%)
What is the function of osteoblasts?
Synthesise osteoid and participate in mineralisation/calcification of osteoid
(Bone deposition)
What is the function of osteoclasts?
Release lysosomal enzymes which break down bone
Bone resorption
What is the function of osteocytes?
Make type I collagen and other extracellular matrix components
How does the differentiation of osteoclasts occur from osteoblasts?
RANKL is expressed on the surface of osteoblasts
RANKL binds to RANK-R to stimulate osteoclast formation and activity
What is osteoprotegerin?
A protein which is a decoy receptor for RANKL; inhibits osteoclast differentiation
What are the two key hormones that regulate bone remodelling and calcium balance?
Parathyroid hormone (PTH) Calcitriol
What stimulates PTH release?
Hypocalcaemia
How is calcitriol produced?
Inactive vitamin D is synthesised in the skin
Converted to calcidiol in the liver
Converted to calcitriol in the kidney
How does hypercalcaemia affect nerve and skeletal muscle excitability?
Ca²⁺ blocks Na⁺ influx, so less membrane excitability
How does hypocalcaemia affect nerve and skeletal muscle excitability?
Enables greater Na⁺ influx, so more membrane excitability
What are the signs and symptoms of hypocalcaemia?
- Parasthesia (hands, mouth, feet, lips)
- Convulsions
- Arrhythmias
- Tetany
What is Chvostek’s Sign? What does this indicate?
The facial nerve is tapped just below the zygomatic arch
Positive response= twitching of facial muscles
Indicates neuromuscular irritability due to hypocalcaemia
What is Trousseau’s sign? What does this indicate?
Inflation of blood pressure cuff for several minutes induces carpopedal spasm (painful spasm)
Neuromuscular irritability due to hypocalcaemia
What are the possible causes of hypocalcaemia?
1) Vitamin D deficiency
2) Low PTH levels = hypoparathyroidism
- Surgical- neck surgery
- Autoimmune
3) PTH resistance
(e. g. Pseudohypoparathyroidism)
4) Renal
- Impaired 1α hydroxylation → decreased production of 1, 25(OH)₂D₃
What are the signs and symptoms of hypercalcaemia?
1) Kidney stones
- polyurea and thirst
- nephrocalcinosis, renal colic, chronic renal failure
2) Abdominal moans - G.I. Effects
- anorexia, nausea, dyspepsia, constipation, pancreatitis
3) Psychic groans
- fatigue, depression, impaired concentration, altered mentation, coma (usually >3mmol/L)
What are the causes of hypercalcaemia?
1) Primary hyperparathyroidism
2) Malignancy- tumours/metastases
(often secrete a PTH-like peptide)
3) Conditions with a high bone turnover
(hyperthyroidism, Paget’s disease of bone- immobilised patient)
4) Vitamin D excess (rare)
What causes hypercalcaemia and high PTH? Why are they both high?
Primary hyperparathyroidism
(adenoma secreting PTH)
PTH increases serum Ca²⁺ which provides negative feedback to parathyroid, ineffective due to autonomous PTH secretion
What Ca²⁺ and PTH levels would you expect to see in hypercalcaemia of malignancy? Why?
High Ca²⁺
Low PTH
Malignancy causes release of PTH-related peptide which behaves exactly like PTH causing increase of serum Ca²⁺
Normal PTH is low because of negative feedback from Ca²⁺
What are the effects of calcitriol?
1) Stimulates intestinal absorption of Ca²⁺ (and Mg²⁺) and PO₄³⁻. This provides the ions necessary for normal bone mineralisation
2) Regulates osteoblast differentiation
3) Increases renal Ca²⁺ reabsorption, decreases PO₄³⁻ reabsorption via FGF23- a hormone produced by bone which increases urine PO₄³⁻ excretion
What does vitamin D deficiency result in, in adults and children? What are the symptoms?
In children: Rickets
In adults: Osteomalacia
Results in softening of bone, bone deformities, bone pain and severe proximal myopathy
Where is vitamin D synthesised?
In the skin by converting UVB light
What part of the process of production of active vitamin D occurs in the liver?
25 hydroxylation
Vitamin D → 25 OH-D
What part of the process of production of vitamin D occurs in the kidneys? What enzyme catalyses this reaction?
1 hydroxylation catalysed by 1α-hydroxylase (stimulated by PTH)
25 OH-D → 1, 25 (OH)₂D
What are the causes of vitamin D deficiency?
1) Diet
2) Lack of sunlight
3) G.I. malabsorption
e. g. coeliac disease, inflammatory bowel disease
4) Renal failure, liver failure
5) Vitamin D receptor defects (autosomal recessive, rare, resistant to vitamin D treatment
What causes secondary hyperparathyroidism?
Low Ca²⁺due to vitamin D deficiency. PTH increases appropriately to try to normalise serum calcium
How do you diagnose a vitamin D deficiency?
- Plasma [25(OH)D₃] usually low
- Plasma [Ca²⁺] low (may be normal if secondary hyperparathyroidism has developed)
- Plasma [PO₄³⁻] low (as vitamin D required to absorb it in the gut)
- [PTH] high (secondary hyperparathyroidism)
- Radiological findings (variable)
e. g. widened osteoid seams
Where is 1α hydroxylase produced?
In the kidney
How does renal failure contribute to hypocalcaemia?
1) Cannot produce 1α hydroxylase, so there is decreased Ca²⁺ absorption causing hypocalcaemia
2) As renal function decreases PO₄³⁻ excretion decreases which causes elevated PO₄³⁻ in the plasma. PO₄³⁻ binds calcium which decreases serum Ca²⁺ further
What are Brown tumours?
Radiolucent bone lesions.
They reflect excessive osteoclastic bone resorption secondary to high PTH
What is 25 hydroxy vitamin D₂?
Ergocalciferol
What is 25 hydroxy vitamin D₃?
Cholecalciferol
What treatment is given to patients with vitamin D deficiency if they have normal renal function?
Give 25 hydroxy vitamin D (25 (OH) D)
Patient can convert this to 1, 25 (OH)₂ D via 1α hydroxylase
What treatment is given to patients with vitamin D deficiency if they have renal failure?
Patient will have inadequate 1α hydroxylase so they cannot activate 25 (OH) D
They must be given Alfacalcidol- 1α hydroxycholecalciferol
What can result from vitamin D excess (intoxication)?
Can lead to hypercalcaemia and hypercalciuria due to increased intestinal absorption of calcium
What can cause vitamin D intoxication?
1) Excessive treatment with active metabolites of vitamin D
e. g. Alfacalcidol
2) Granulomatous disease
e. g. sarcoidosis, leprosy and tuberculosis (macrophages in the granuloma produce 1α hydroxylase to convert 25(OH)D to the active metabolite 1, 25(OH)₂D
What is osteoporosis? How is it measured?
Defined as having a bone mineral density (BMD) that is 2.5 standard deviations or more below the average value for young healthy adults.
Measured by Dual Energy X-ray Absorptiometry (DEXA)
What are the pre-disposing conditions for osteoporosis?
1) Post-menopausal oestrogen deficiency
2) Age-related deficiency in bone homeostasis (men and women)
e. g. osteoblast senescence
3) Hypogonadism in young women and in men
4) Endocrine conditions
- Cushing’s syndrome
- Hyperthyroidism
- Primary hyperparathyroidism
5) Iatrogenic
- Prolonged cause of glucocorticoids
- Heparin
What are the treatment options for osteoporosis?
1) Oestrogen/selective oestrogen receptor modulators
2) Bisphosphonates
3) Denosumab
4) Teriparatide
What are the effects of treating post-menopausal women with pharmacological doses of oestrogen?
- Antiresorptive effects on the skeleton
- Prevents bone loss
Why do post-menopausal women with an intact uterus need additional progesterone when on HRT?
To induce a bleed to prevent endometrial hyperplasia
Why is the use of HRT limited?
- Increased risk of breast cancer
- Venous thromboembolism
What are the different types of SERMs? What do they do? Give examples.
Selective oEstrogen Receptor Modulators:
1) Tissue-selective ER antagonist
e. g. tamoxifen
- Antagonises ERs in breast but has oestrogenic activity in bone
- Oestrogenic effects on endometrium limit it’s use in osteoporosis management
2) Tissue selective ER agonist
e. g. raloxifen (further developed for it’s selectivity on bone)
- Oestrogenic activity in bone. Anti-oestrogenic at breast and uterus
- Risks include venous thromboembolism and stroke
What do bisphosphonates do?
- Bind avidly to hydroxyapatite and ingested by osteoclasts - impair ability of osteoclasts to reabsorb bone
- Decrease osteoclast progenitor development and recruitment
- Promote osteoclast apoptosis
NET RESULT: Reduced bone turnover
What conditions are bisphosphonates used for?
1) Osteoporosis- first line treatment
2) Malignancy
- Associated hypercalcaemia
- Reduce bone pain from metastases
3) Paget’s disease- reduce bony pain
4) Severe hypercalcaemic emergency- I.V. initially (rehydration first)
What are the unwanted actions of bisphosphonates?
1) Oesophagitis
- may require switch from oral to IV preparation
2) Flu-like symptoms (IV)
- often limited to first dose
3) Osteonecrosis of the jaw
- greatest risk in cancer patients receiving IV bisphosphonates
4) Atypical fractures
- may reflect over-suppression of bone remodelling in prolonged bisphosphonate use
How does denosumab inhibit bone resorption? How is it administered?
It is a human monoclonal antibody
- Binds RANKL inhibiting osteoclast formation and activity
- Hence inhibits osteoclast-mediated bone resorption
Administered as a subcutaneous injection every 6 months. 2nd option following bisphosphonates
What is teriparatide?
Recombinant PTH fragment- amino-terminal 34 amino acids of native PTH
Increases bone formation and bone resorption, but formation outweighs resorption
Subcutaneous injection
What are the options for treatment of osteoporosis in the order that they would be given?
1) Bisphosphonates
2) Denosumab
3) Teriparatide
What is Paget’s disease?
Accelerated, localised but disorganised bone remodelling
Excessive bone resorption (↑ osteoclast activity) followed by a compensatory increase in bone formation leads to a formation of woven bone (structurally disorganised)- mechanically weaker than normal adult lamellar bone
Results in:
- Bone fragility
- Bone hypertrophy and deformity
What is the presentation of Paget’s disease?
Most patients are asymptomatic
Characterised by abnormal, large osteoclasts- excessive in number
What are the clinical features of Paget’s disease?
- Skull, thoracolumbar spine, pelvis, femur and tibia most commonly affected
- Arthritis
- Fracture
- Pain
- Bone deformity
- Increased vascularity (warmth over affected bone)
- Deafness- cochlear involvement
- Radiculopathy- due to nerve compression
How is Paget’s disease of bone diagnosed?
- Plasma [Ca²⁺] normal
- Plasma [alkaline phosphatase] usually increased
- Plain xrays:
• Lytic lesions (early)
• Thickened, enlarged, deformed bones (later) - Radionuclide bone scan demonstrates extent and locations of skeletal involvement
What are the treatment options for Paget’s disease?
1) Bisphosphonates
- very helpful for reducing boney pain and disease activity
2) Simple analgesia
If a patient has high calcium and low phosphate with high PTH what would the diagnosis be?
Primary hypoparathyroidism
What is the definitive treatment of primary hyperparathyroidism?
Remove parathyroid with adenoma
What is the likely diagnosis if a patient has high calcium and low PTH?
Malignancy producing PTHrp
What is the treatment for a patient who has a malignancy producing PTHrp resulting in high calcium and low PTH?
Treat with bisphosphonates
What is the key brain area involved in the regulation of food intake?
The arcuate nucleus
How is the arcuate nucleus able to monitor food intake?
Has an incomplete blood-brain barrier which allows access to peripheral hormones. It integrates peripheral and central feeding signals
What are the two neural populations in the arcuate nucleus?
1) Stimulatory
(NPY/Agrp neurons)
2) Inhibitory
(POMC neuron)
What is the role of NPY/Agrp neurons in the arcuate nucleus?
Increase appetite
What is the role of POMC neurons in the arcuate nucleus?
Decrease appetite
How does POMC decrease appetite?
POMC is cleaved to produce α-MSH, an agonist of MC4R.
α-MSH activates MC4R which decreases food intake
Where is the melanocortin 4 receptor located?
MC4R is located in the paraventricular nucleus
How does Agrp work to increase appetite?
It is an endogenous antagonist. It blocks the MC4R receptor and blocks α-MSH signalling which increases food intake
What do POMC and MC4R mutations result in?
Obesity
How does a POMC mutation present?
Hungry all the time
No cortisol regulation
Pale skin and red hair
What was the presentation of the ob/ob mouse?
Similar to a starved animal (minus diabetes and obesity) Recessive mutation - Profoundly obese - Diabetic - Infertile - Stunted linear growth - Decreased body temperature - Decreased energy expenditure - Decreased immune function Missing leptin!
What leptin level will a person with low body fat have?
Low
What effect does central or peripheral administration of leptin have?
- Decreases food intake
- Increases thermogenesis
What effect does leptin have on the arcuate nucleus?
Activates POMC
Inhibits NPY/ Agrp neurons
What leptin level will a person with high body fat have?
High
The presence of leptin tells the brain what?
That the body has sufficient fat reserves for normal functioning
Insulin circulates at levels proportional to what?
Body fat
Ghrelin regulates food intake when combined with what enzyme?
Ghrelin O-acyltransferase
GOAT
What effect does ghrelin have on neurons in the arcuate nucleus?
- Stimulates NPY/Agrp neurons
- Inhibits POMC neurons
- Increases appetite
What do L cells secrete?
L cells sense what is going on in the gut. They cause a wave of Ca²⁺ down the gut and exocytosis of gut hormones
L cells secrete PYY and GLP-1
How big is Peptide YY? What amino acids are in the active form?
36 amino acids long
Cleaved to 3-36 AA in the active form
What effect does PYY have on neurons in the arcuate nucleus?
- Inhibits NPY release
- Stimulates POMC
- Decreases appetite
What does glucagon-like peptide-1 do?
Important in stimulating glucose-stimulated insulin release (incretin role) and also reduces food intake
Why is GLP-1 not used as a treatment for obesity?
Poor half-life
Effective but it is inactivated very easily
What is Saxenda?
A long-acting glucagon-like peptide-1 receptor agonist
What are the limitations of using PYY as a drug target?
It has a narrow therapeutic window:
- Above the correct dose causes nausea
- Below has no effect on appetite
Different people respond to the drug differently. It also has a short half life
What comorbidities are associated with obesity?
- Depression
- Sleep apnoea
- Bowel cancer
- Osteoarthritis
- Gout
- Stroke
- Myocardial infarction
- Hypertension
- Diabetes
- Peripheral vascular disease
As a percentage how likely is obesity inherited?
60-80%
What is the “Thrifty Gene Hypothesis”?
Suggests specific genes were selected to increase metabolic efficiency and fat storage.
It was evolutionary sensible to put on weight
Thin humans didn’t survive famines, so they didn’t pass on their genes to modern humans
What is the “Adaptive Drift Hypothesis”?
Normal distribution of body weight:
- The fat are eaten
- The thin starve
When humans learned to defend against predators obesity was not selected against. Putting on body fat then a neutral change (genetic drift). In current context, the inheritors of these genes become obese
What is cachexia? What type of diabetes is it associated with?
Weakness and wasting of the body die to a chronic condition.
Associated with type 1 diabetes
What type of type I diabetes occurs when a patient is over 40?
Latent autoimmune diabetes in adults (LADA)
What is the mechanism of Maturity Onset Diabetes of the Young?
Single gene mutation in the insulin receptor; presents at a young age phenotypically as Type I or type II
Mutations of transcription factor genes, glucokinase gene
What type of diabetes has a maternal predisposition?
Mitochondrial diabetes
What causes type I diabetes onset?
An environmental trigger initiates autoimmune destruction of islets
What causes type II diabetes onset?
Genetic predisposition and obesity lead to insulin resistance causing hyperglycaemia.
Why do patients with type II diabetes get β-cell failure?
Because they become resistant to insulin the pancreas has to produce so much that the cells start to fail.
What peptide is released with insulin, that is used to detect low insulin release?
C-peptide
What is the Honeymoon phase in type I diabetes?
Where the pancreas produces the last amount of insulin before it completely fails; then the patient permanently has type I diabetes
Which HLA-DR alleles significantly increase the genetic susceptibility to type I diabetes?
HLA-DR3
HLA-DR4
What environmental factors increase the prevalence of type I diabetes?
Season. Onset is more common in autumn and winter. Suggests this could be due to infection
What markers are typically used to measure diabetes?
Islet cell antibodies (ICA)- group O human pancreas
Glutamic acid decarboxylase (GADA) - widespread neurotransmitter
What are the signs and symptoms of type I diabetes?
Symptoms
- Polyuria
- Nocturia
- Polydispia
- Blurred vision
- ‘Thrush’
- Weight loss
- Fatigue
Signs
- Dehydration
- Cachexia
- Hyperventilation
- Smell of ketones
- Glycosuria
- Ketonuria
How is fat stored in adipocytes? What is this fat broken down into?
Triglyceride, broken down into glycerol + fatty acids
What happens to glycerol from adipocytes when triglycerides have been broken down? What hormones stimulate this?
It is transported to the liver where it enters the Kreb’s cycle to produce glucose.
Stimulate by catecholamines and growth hormone
What happens to fatty acids from adipocytes once glycerol has been broken down?
The fatty acids are transported to the liver where they produce ketones
What are ketones used as a marker for?
Insulin deficiency
What are the long term complications associated with diabetes?
- Retinopathy
- Nephropathy
- Neuropathy
- Vascular disease
What is the recommended diet in a type I diabetes patient?
- Reduce calories as fat
- Reduce calories as refined carbohydrate
- Increase calories as complex carbohydrate
- Increase soluble fibre
- Balanced distribution of food over the course of the day with regular meals and snacks
When is insulin treatment administered and how long does it last?
With Meals: - Short acting - Human insulin - Insulin analogue (e.g. Lispro, Aspart, Glulisine) Background - Long acting - Non-c bound to zinc or protamine - Insulin analogue (e.g. Glargine, Determir, Degludec)
How does HbA1c indicate glucose levels? What is this measure used for?
HbA1c red cells reacts with glucose irreversibly. This gives a good long-term measure of glycaemic control and is related to the risk of complications
Lowering HbA1c is associated with a lower risk of complication particularly microvascular complications
What are the acute complications of type I diabetes?
Ketoacidosis
1) Hyperglycaemia
- reduced tissue glucose utilisation
- increased hepatic glucose production
2) Metabolic acidosis
- circulating acetoacetate and hydroxybutyrate
- Exacerbated by osmotic dehydration and poor tissue perfusion
What plasma glucose level defines hypoglycaemia?
<3.6mmol/L
What is severe hypoglycaemia?
Any hypo requiring help of another person to treat
At what glucose level are mental processes impaired?
<3mmol/L
At what glucose level is consciousness impaired?
<2mmol/L
What are the signs and symptoms of increased autonomic activation caused by hypoglycaemia?
- Palpitations (tachycardia)
- Tremor
- Sweating
- Pallor/cold extremities
- Anxiety
What are the signs and symptoms of impaired CNS function caused by hypoglycaemia?
- Drowsiness
- Confusion
- Altered behaviour
- Focal neurology
- Coma
How is hypoglycaemia treated in a conscious patient?
Oral
- Food
- Glucose (solution or tablets)
- complex carbohydrate (to maintain blood glucose after initial treatment)
How is hypoglycaemia treated in an unconscious patient?
- IV dextrose
(e. g. 10% glucose infusion) - 1mg glucagon IM
- Avoid concentrated solutions if possible
(e. g. 50% glucose)
What type of diabetes is ketosis prone?
Type I diabetes mellitus
Although can occur in type II
What fasting blood glucose level is diagnostic of diabetes? What does this increase to following glucose administration?
Fasted: >7.0mmol/L
2 hours: >11.1mmol/L
What are a normal fasting glucose and 2 hour reading following glucose administration?
Fasted: 4-6mmol/L
2 hours: <7.8mmol/L
What range is diagnostic of impaired glucose tolerance for both fasting and 2 hours following glucose administration?
Fasted: 6.1-6.9mmol/L
2 hours: 7.9-11mmol/L
What result would indicate diabetes following a random blood test?
> 11.1mmol/L
In what country is type II diabetes most common?
India
What factors are thought to predispose patients to MODY?
Maturity Onset Diabetes of the Young
- Genetics
- Intrauterine calorie restriction
- Low birth weight
- Some fatty acids damage insulin secretion
What is the inheritance pattern of MODY?
Autosomal dominant
What type of diabetes is more genetic?
Type II diabetes
How many type II diabetes patients are obese?
80%
What happens to cholesterol in type II diabetes?
Patients get dyslipidaemia
How does insulin release usually occur in a healthy patient?
First phase response after eating a meal- regulated by GLP-1 (stored insulin), then gradual release as β-cells produce insulin
What is glucose converted into in muscle?
Glycogen
What process converts glycerol into glucose?
Gluconeogenesis
Where does the liver get most of it’s fatty acids from?
Omental fat
What protein is thought to be responsible for the mechanism of type II diabetes?
Adiponectin
What type of obesity drives changes to metabolism which predispose to type II diabetes?
Central or omental obesity
What is a common side effect of diabetes treatments?
Weight gain
What is the presentation of type II diabetes?
- Osmotic symptoms
- Infections
- Screening test
- Presentation with complications
Acute; hyperosmolar coma
Chronic; ischaemic heart disease, retinopathy
What are the complications of type II diabetes?
1) Microvascular
- retinopathy
- nephropathy
- neuropathy
2) Macrovascular
- Ischaemic heart disease
- Cerebrovascular
- Renal artery stenosis
- PVD
3) Metabolic
- Lactic acidosis
- Hyperosmolar
4) Treatment
- Hypoglycaemia
What is the basic management of type II diabetes mellitus?
1) Education
2) Diet
3) Pharmacological treatment
4) Complication screening
What diet is recommended in type II diabetes mellitus?
- Control total calories/increase exercise (weight)
- Reduce refined carbohydrate (less sugar)
- Increase complex carbohydrate (more rice etc)
- Reduce fat as proportion of calories (less IR)
- Increase unsaturated fat as proportion of fat (IHDL)
- Increase soluble fibre (longer to absorb carbohydrate)
What is monitored during type II diabetes?
- Weight
- Glycaemia
- Blood pressure
- Dyslipidaemia
What is the most effective drug to treat diabetes mellitus?
Metformin
What patients are prescribed metformin? How does metformin work? Give examples.
Overweight patients with type II diabetes where diet alone has not succeeded
Reduces insulin resistance
- Reduced hepatic glucose output
- Increases peripheral glucose disposal
GI side effects
Do not use if severe liver, severe cardiac or mild renal failure
e.g. biguanide
What is the mechanism of action of glibenclamide?
Enters β-cells and blocks K⁺ channel (like glucose); voltage change activates Ca⁺ channel which causes an influx of Ca⁺ which stimulates the release of insulin (mimics and increases the insulin response)
What patients are prescribed sulphonylurea? What are the side effects? Give examples.
Lean patients with type II diabetes where diet alone has not succeeded
Side effects: hypoglycaemia, weight gain
e.g. Glibenclamide
How does arbose work? What are the side effects?
Alpha glucosidase inhibitor
Prolongs absorption of oligosaccharides. Allows insulin secretion to cope, following defective first phase insulin
As effective as metformin
Side effects flatus
How do thiazolidinediones work? What are the side effects? Give an example
Peroxisome proliferator-activated receptor agonists PPAR-Y
Insulin sensitizer, mainly peripheral
Adipocyte differentiation modified, weight gain but peripheral not central
Improvement in glycaemia and lipids
Side effects: older types of hepatitis and heart failure
What hormone is responsible for an increased response to insulin if it is taken orally compared to if it is administered intravenously? What else does this hormone do?
GLP-1 is secreted in response to nutrients which stimulates insulin and suppresses glucagon
Increases satiety
Restores β-cell glucose sensitivity
Why can GLP-1 not be used as a drug to treat diabetes?
It has a short half-life, and is rapidly degraded by enzyme dipeptidyl peptidase-4 (DPPG-4)
How do GLP-1 agonists work? Give examples?
Injectable; long-acting
Decrease [glucagon] and [glucose]
Weight loss
e.g. Exenatide, liraglutide
How do gliptins work?
DPPG-4 inhibitor Increase the half life of exogenous GLP-1 Increase [GLP-1] Decrease [glucagon] and [glucose] Neutral on weight
How does empagliflozin work?
Inhibits Na-Glu transporter, increases glycosuria
Side effects: UTIs
Other than glycaemia what other factors need to be controlled in type II diabetes petients?
Blood pressure
- In possibly 90% of patients
Diabetic dyslipidaemia
- causes ↑ cholesterol; ↑ triglyceride; ↓HDL
What is the most effective method for reduction of incidence in type II diabetes?
Lifestyle changes
What type of diabetes is more prevalent?
Type II
What type of diabetes has acute onset?
Type I
What type of diabetes has gradual onset?
Type II
What type of diabetes is more common in caucaseans?
Type I
What could precipitate diabetic ketoacidosis?
- New diagnosis of type I diabetes mellitus
- Not taking insulin
- Incurrent stress (e.g. pneumonia, heart attack)
- Fasting and not taking enough insulin
What will happen if there is deficient [insulin]?
High hepatic glucose output and deficient muscle glucose uptake
What causes hyperglycaemia?
Insulin deficiency
Stress hormone
What causes ketosis?
Insulin deficiency
Stress hormone
Fasting
Why does HCO₃⁻ concentration decrease with diabetic ketoacidosis?
- Impaired production from the pancreas
- Increased H⁺ buffering
What are the clinical features of diabetic ketoacidosis?
- Dehydration
- Insulin deficiency
- Total body K⁺ deficiency, although plasma [K⁺] high
- Acidotic
- Risk of arrhythmia, infection and dilated stomach
- Polyuria and polydipsia due to osmotic diuresis
- Hyperventilation (Kussmaul)
- Abdominal pain, vomiting
- Coma
- Glycosuria and ketonuria
What investigations are conducted for diabetic ketoacidosis?
- Capillary glucose
- Plasma glucose
- Creatinine, K⁺, Na⁺
- FBC
- Arterial blood gases
- Amylase (triglyceride)
- ECG
- CXR (chest X-ray)
- Septic screen
What is the treatment for diabetic ketoacidosis?
1) Fluid (H₂O 100ml/kg; Na⁺ 8mmol/kg in 24 hours) 2) Insulin 3) Potassium 4) Bicarbonate 5) Other measures - Cardiac monitor (arrhythmias) - Catheterise - Antibiotics - Nasogastric tube (gastroparesis) - Consider heparin - Consider arterial line (very acidotic) and central line (elderly or when cardiac failure)
What are the dangers associated with acidaemia?
- Negative inotropism
- Peripheral vasodilation
- Hypotension
- Cerebral inhibition
What are the dangers associated with bicarbonate?
- Hypokalaemia
- Hypernatraemia
- Rebound alkalosis
- CSF acidosis
- Impaired oxyHb dissociation
How do you prevent diabetic ketoacidosis?
- Education
- Never stop insulin
- Check glucose and modify insulin if ill
- Admit if vomiting
What stimulates and inhibits proteolysis?
Stimulates: Cortisol
Inhibits: Insulin
What stimulates protein synthesis?
Insulin Growth hormone (IGF-1)
What is the hepatic glucose output after a 10 hour fast?
25%
What sites are affected by microvascular complications of diabetes?
1) Retinal arteries
2) Glomerular arterioles (kidney)
3) Vasa nervorum (tiny blood vessels that supply nerves)
What percentage HbA1c is indicative of type II diabetes?
> 6.5%
What factors increase the risk of microvascular complications?
1) Severity of hyperglycaemia
2) Hypertension
3) Genetic
4) Hyperglycaemic memory
5) Tissue damage through originally reversible and later irreversible alterations in proteins
What are the clinical features of background diabetic retinopathy?
- Hard exudates (cheese colour, lipid)
- Microaneurysms (“dots”)
- Blot haemorrhages
What are the clinical features of pre-proliferative diabetic retinopathy?
- Cotton wool spots also called soft exudates
- Represent retinal ischaemia
What are the clinical features of proliferative diabetic retinopathy?
- Visible new vessels
- On disk or elsewhere in retina
What are the clinical features of maculopathy?
- Hard exudates near the macula
- Same disease as background, but happens to be near the macula
- Changes around the macula affect colour vision
- This can threaten direct vision
What is the management procedure for background diabetic retinopathy?
- Improve control of blood glucose
- Warn patient that warning signs are present
What is the management procedure for pre-proliferative diabetic retinopathy?
Suggests general ischaemia; if left alone new vessels will grow
Treated with pan retinal photocoagulation
Also used for proliferative diabetic retinopathy
What is the management procedure for maculopathy?
Needs only a grid of photocoagulation
What are the clinical features of diabetic nephropathy?
- Hypertension
- Progressively increasing proteinuria
- Progressively deteriorating kidney function
- Classic histological features
What histological glomerular changes occur in diabetic nephropathy?
- Mesangial expansion
- Basement membrane thickening
- Glomerulosclerosis
What is the prevalence of diabetic nephropathy in type I diabetes?
20-40%
What are the strategies for intervention in diabetic nephropathy?
1) Hyperglycaemia control
2) Blood pressure control
3) Inhibition of the activity of RAS system
4) Stop smoking
5) Dyslipidaemia control
6) Education
What receptors does Angiotensin 2 act on?
AT₁ and AT₂ receptor
What causes diabetic neuropathy?
The small vessels supplying the nerves, called the vasa nervorum, become blocked
What are the different types of diabetic neuropathy?
1) Peripheral polyneuropathy
2) Mononeuropathy
3) Mononeuritis multiplex
4) Radiculopathy
5) Autonomic neuropathy
6) Diabetic amyotrophy
What is peripheral neuropathy? Who is most likely to get it?
- Longest nerves supply feet
- Loss of sensation
- More common in tall people and patients with poor glucose control
- Danger is that patients will not sense an injury to the foot (e.g. stepping on a nail)
What are the clinical features of peripheral neuropathy?
- Loss of ankle jerks
- Loss of vibration sense (using tuning fork)
- Multiple fractures on foot X-ray (Charcot’s joint)
What is mononeuropathy?
- Usually sudden motor loss
- Wrist drop, foot drop
- Cranial nerve palsy:
• most commonly double vision due to 3rd nerve palsy
What is pupil sparing third nerve palsy?
Eye is usually “down and out” (6th nerve pulls eye out and 4th nerve pulls it down)
Pupil does respond to light
What would cause a third nerve palsy with a fixed dilated pupil?
Could be an aneurysm pressing on the parasympathetic fibres
Patients need a CT as they could have a tumour
What is mononeuritis multiplex?
A random combination of peripheral nerve lesions
What is radiculopathy?
Pain over spinal nerves, usually affecting a dermatome on the abdomen or chest wall
What is an autonomic neuropathy?
Loss of sympathetic and parasympathetic nerves to the GI tract, bladder and cardiovascular system
Difficult to treat
What effect does autonomic neuropathy have on the GI tract?
- Difficulty swallowing
- Delayed gastric emptying
- Constipation/nocternal diarrhoea
- Bladder dysfunction
What effect does autonomic neuropathy have on the cardiovascular system?
- Postural hypotension (can be disabling)
- Cardiac autonomic supply
(case reports of sudden cardiac death)
What are the clinical signs of autonomic neuropathy?
- Measure changes in heart rate in response to Valsalva manoeuvre
- Normally there is a change in heart rate
- Look at ECG and compare R-R intervals
What complications are associated with macrovascular disease?
- Early widespread atherosclerosis
- Ischaemic heart disease
- Cerebrovascular disease
- Peripheral vascular disease
- Renal artery stenosis
What are the stages in atheroma formation?
1) Initial lesion
2) Fatty streak
3) Intermediate
4) Atheroma
5) Fibroatheroma
6) Complicated
What factors increase the risk of macrovascular complications?
- Fasting glucose >6mmol/L
- Waist circumference
Men: >102
Women: >88 - HDL
Men: <1.0
Women: <1.3 - Hypertension >135/80
- Insulin resistance
- Inflammation
- Adipocytokines
- Urine Microalbumin
What effect does hyperglycaemia have on life expectancy?
Significantly reduces life expectancy
Microvascular disease causes morbidity; macrovascular disease causes morbidity and mortality
What is the biggest cause of morbidity and mortality in diabetics?
Ischaemic heart disease
How is cerebrovascular disease different in diabetics?
It occurs earlier than without diabetes and is more widespread
What complications associated with diabetes are caused by peripheral vascular disease?
Diabetic foot and problems with neuropathy
What complications associated with diabetes does renal artery stenosis contribute to?
Hypertension
Renal failure
Why is hyperglycaemia alone not treated in diabetes?
Hyperglycaemia alone has a minor effect on increased risk of cardiovascular disease. Must aggressively treat multiple risk factors (e.g. BP and cholesterol)
What are the non-modifiable risk factors for macrovascular disease?
- Age
- Sex
- Birth weight
- FH/Genes
What are the modifiable risk factors for macrovascular disease?
- Dyslipidaemia
- High blood pressure
- Smoking
- Diabetes
What is the name of the systemic disease of multiple arterial beds?
Macrovascular disease
What is the pathway to foot ulceration in diabetes?
1) Sensory neuropathy
2) Motor neuropathy
3) Limited to joint mobility
4) Autonomic neuropathy
5) Peripheral vascular disease
6) Trauma- repeated minor/discrete episode
7) Reduced resistance to infection
8) Other diabetic complications e.g. retinopathy
What tool is used to predict neuropathy and ulceration in the feet? How does it work?
Nylon microfilament
Bends when you have applied 10g of pressure to the skin
What is used as a marker for joint adjustment in diabetic neuropathy?
Loss of vibration sense
What is used to improve peripheral vascualr disease?
Angioplasty
Describe the neuropathic foot.
Numb, warm, dry, palpable foot pulses, ulcers at points of high pressure loading
Describe the ischaemic foot.
Cold, pulseless, ulcers at the foot margins
Describe the neuro-ischaemic foot.
Numb, cold, dry, pulseless, ulcers at points of high pressure loading and at foot margins
How do you assess the foot of a diabetic patient?
1) Appearance (deformity, callus) 2) Feel (hot/cold, dry) 3) Foot pulses (dorsalis pedis / posterior tibial pulse) 4) Neuropathy (vibration sensation, temperature, ankle jerk reflex, fine touch sensation)
What is the preventative management of diabetic foot?
1) Control diabetes
2) Inspect feet daily
3) Have feet measured when buying shoes
4) Buy shoes with laces and square toe box
5) Inspect inside of shoes for foreign objects
6) Attend chiropodist
7) Cut nails straight across
7) Care with heat
8) Never walk barefoot
What is the management procedure of foot ulceration in a diabetic patient?
1) Relief of pressure
- bed rest (risk of DVT, heel ulceration)
- redistribution of pressure / total contact cast
2) Antibiotics, possibly long term
3) Debridement
4) Revascularisation
- angioplasty
- arterial bypass surgery
5) Amputation
What are the symptoms of osteomyelitis in the diabetic foot?
- Hot red foot with ulcer
- Forefoot: MTP’s IPs
- Hindfoot: calcaneus
- MRI: marrow oedema in forefoot and hindfoot near ulcer
What are the symptoms of active Charcot’s in the diabetic foot?
- Hot red foot with no ulcer
- Midfoot: subarticular
- MRI: marrow oedema in midfoot subchondral
When you eat a meal insulin binds to a receptor on adipocytes. What is then taken into the cell?
Glucose via GLUT4
Potassium
Phosphate
What symptoms presents in diabetic ketoacidosis to compensate for acidic blood?
Air hunger
blow off carbon dioxide
Why is it impossible that a patient with type II diabetes is not ketotic?
Because they produce high levels of insulin because they are resistant, which turns off ketogenesis
What is the diagnosis if a patient has
Fasting glucose: 7.4mM
Following GTT, 2 hour value: 7.7mM
Type II diabetes
What treatment has been proven to prevent diabetes in the diabetes prevention programme?
Metformin (Biguanide) Lifestyle changes (diet and exercise)
