Endocrinology Flashcards
Which hormones are secreted by the anterior pituitary gland?
- FSH (follicle stimulating hormone)
- LH (Luteinising hormone)
- ACTH (adrenocorticotrophic hormone)
- TSH (thyroid stimulating hormone)
- GH (growth hormone)
- PRL (Prolactin)
What hormones are released by the posterior pituitary gland?
- ADH (anti-diuretic hormone)
- Oxytocin
What are the causes of hyperprolactinaemia? (high levels of prolactin)
- Pregnancy, suckling
- Prolactinoma (benign pituitary adenoma)
- PCOS
- Primary hypothyroidism (TRH increases)
- Anti-emetics such as Metoclopramide and Domperidone (dopamine receptor antagonist)
And antipsychotics which are also dopamine antagonists
What stimulates prolactin release from the anterior pituitary gland?
TRH (thyrotropin releasing hormone)
What inhibits prolactin release?
Dopamine (secreted from the hypothalamus)
what are the symptoms of prolactinoma?
- menstrual cycle dysfunction
- galactorrhoea
What is the treatment for a prolactinoma?
- Bromocriptine or Cabergoline
Both are dopamine receptor agonists (increasing dopamine levels and thus inhibiting prolactin release) - If a macroprolactinoma or failed medical therapy then surgical resection of the tumour
How do Domperidone and Metoclopramide cause hyperprolactinaemia?
They block dopamine receptors –> less dopamine –> less inhibition of prolactin –> prolactin levels go up
Where is GnRH (gonadotropin releasing hormone) released from and what is its function?
- Released from the hypothalamus
- Stimulates the anterior pituitary to secrete FSH and LH
What is the classical eye finding in a pituitary adenoma?
A. Bitemporal hemianopia
Occurs due to compression of the optic chiasm and causes tunnel vision
What are the symptoms of a non-functioning pituitary adenoma?
A non-functioning pituitary adenoma is usually benign and is non-secretory
However it can cause:
1. Visual symptoms due to compression
2. Headache
3. Hypopituitarism due to pressure of the normal tissue
4. The “stalk effect” causing slightly elevated levels of prolactin (not as high as in prolactinoma)
What are the symptoms of hyperprolactinaemia in women?
- amenorrhoea
- infertility
- galactorrhoea
- osteoporosis
high Prolactin inhibits GnRH - the inhibiting ovulation
What are the symptoms of hyperprolactinaemia in men?
- Impotence
- loss of libido
- galactorrhoea
What are the symptoms of hypercalcaemia?
Bones - aching bones, muscle weakness
Groans - Abdominal pain, nausea, vomiting, constipation, pancreatitis
Stones - Kidney stones, urinary frequency
Psychiatric moans - confusion, mood changes
What are the blood results in primary hyperparathyroidism?
- High calcium
- Low phosphate
- HIGH ALP (increased bone turnover)
- PTH is high or inappropriately NORMAL (in a healthy patient, PTH would be low in response to high calcium levels for example in bony mets - PTH would be surpassed)
What are the blood results in secondary hyperparathyroidism?
Typically occurs in vit D deficiency and chronic kidney disease - which impairs Vit D activation - thus causing low calcium levels
- Low calcium
- High phosphate
- PTH high (to try and increase Ca levels)
What hormones are secreted by the hypothalamus
- thyrotropin-releasing hormone (TRH)
- gonadotropin-releasing hormone (GnRH)
- Growth hormone-releasing hormone (GHRH)
- corticotropin-releasing hormone (CRH)
- somatostatin (GH inhibiting hormone)
- dopamine
All are released from the hypothalamus and act on the anterior pituitary.
What is the most common form of pituitary tumour?
A prolactinoma (benign adenoma - causing hypersecretion of prolactin)
The hormone prolactin has a negative effect on which hormone?
High prolactin exerts negative feedback on Gonadotropin releasing hormone (GnRH) - it inhibits GnRH which in turn inhibits FSH and LH thus inhibiting ovulation in breast-feeding mothers - natural contraception while breast feeding.
In prolactinoma it leads to infertility and low libido.
The hormone TRH released from the hypothalamus stimulates the anterior pituitary gland to produce which 2 hormones?
thyroid-stimulating hormone (TSH) and prolactin
What is Sheehan syndrome?
Sheehan syndrome is hypopituitarism caused by ischemic necrosis of anterior pituitary gland due to blood loss and hypovolaemic shock.
Most commonly due to post partum haemorrhage
What is the cause of acromegaly?
- A (benign) pituitary adenoma that secretes excess growth hormone
- GH stimulates the release of insulin-like growth factor 1
What is the treatment for acromegaly?
- Transphenoidal surgery
- Octreotide (somatostatin analogue) which supresses GH production
What is toxic multinodular goitre?
- 2nd most common cause of hyperthyroidism
- 2 ore more functioning thyroid nodules that secret excess thyroid hormone
What is Grave’s Disease ?
- An autoimmune disorder causing hyperthyroidism
- Most common cause of hyperthyroidism
- TSH receptor stimulating antibodies
What are the classic symptoms of phaeochromocytoma?
episodes/spells of
- headaches
- palpitations
- diaphoresis
- severe hypertension
Excess adrenaline and noradrenaline
What is a “thyroid storm?”
- severe, acute hyperthyroid state
- Low TSH, high T3/T4
- Tachycardia
- Pyrexia
- precepitated by an acute event such as infection or surgery.
- Typically in an untreated or partially treated patient
- Can occur after radioactive iodine therapy
What is sick euthyroid
- Thyroid function tests show low T3/T4, normal TSH
- May be mistaken for hypothyroidism but pt is clinically euthyroid and the abnormal results are due to acute illness/fasting/trauma/sepsis
What is paraneoplastic Cushing syndrome?
Most commonly associated with small cell lung cancer - ACTH secreting tumour –> stimulates the adrenal gland to produce access cortisol —> Cushing disease
What is the mechanism of hypercalcaemia of malignancy?
1) Paraneoplastic syndrome - cancer cells secrete PTH related protein - typically seen in squamous cell lung ca. PTH low, PTHrP high, Ca2+ high
2) Direct boen destruction by metastases
Low PTH
Low PTHrP
High Ca2+
What is the first step in the management of DKA?
IV fluids - sodium chloride 0.9%
What is the most common pituitary tumour?
prolactinoma
TRH thyrotropin releasing hormone stimulates with hormones to be released from anterior pituitary
TSH
and
Prolactin
What is the function of calcitonin
calcitonin TONES down calcium levels
Used in the treatment of hypercalaemia
Released from thyroid gland
Hashimotos thyroiditis
autoimmune destruction of the thyroid gland
High TSH
T3/T4 low
it is a type of primary hypothyroidism
How do you diagnose Hashimoto’s thyroiditis?
Bloods test - antithyroid peroxidase (anti-TPO) antibody
What eye sign of hyperthyroidism is ONLY present in Grave’s disease?
exophthalmos
occurs due to the autoimmune process causing inflammation around the eye socket
Lid lag can occur with all forms of hyperthyroidism
What is another sign specific to grave’s disease?
pretibial myxedema
Occurs due to increased glycosaminoglycan deposition in the skin
What are some complications of hyperthyroidism?
- thyroid storm
- atrial fibrillation
- osteoporosis
What is the most common type of thyroid cancer?
Papillary thyroid cancer
Has the best Prognosis of all thyroid cancers
Presence of psammoma bodies
Medullary thyroid cancer
5% of all thyroid cancers
A cancer of the parafollicular cells of the thyroid which secret calcitonin
This cancer is associated with MEN IIa and IIb.
What is diabetes insipidus
Insufficient ADH or lack of response to ADH
Intracranial -e.g. posterior pituitary gland not producing ADH
Nephrogenic: kidneys do not respond to ADH
Thus you are unable to re-absorb water properly from the kidneys and unable to concentrate urine
You get:
- polyuria
- polydipsia - increased thirst
- hypernatraemia
- dehydration
How do you diagnose diabetes insipidus?
water deprivation test - which is basically Fluid restriction
Normal response: urine becomes more concentrated/urine osmolality increases
Diabetes inspires: unable to concentrate urine despite fluid restriction - urine output remains high and urine Is still dilute - urine osmolality remains low
How do you differentiate between the different causes of diabetes insipidus?
Administration of desmopressin (ADH analogue)
Intracranial DI - good response to demsopressin and urine concentrates - urine osmolality increases
Nephrogenic DI - no response to desmopressin because the ADH receptors on the kidneys are not working
What is the treatment for nephrogenic diabetes insipidus?
thiazide diuretic
What is the definition of subclinical hypothyroidism?
- high TSH
- Normal thyroxine levels
in a symptomatic patient
What can you use to treat peripheral neuropathy in diabetes?
Neuropathic pain agents such as
- duloxetine - but not recommended if eGFR <30
- amitriptyline
- pregabalin
- gabapentin
What are the important side effects of Metformin?
GI upset
Lactic acidosis (especially if AKI/renal failure)
Can cause B12 deficiency
What is the first line management of hypoglycaemia in an unconscious patient?
20% glucose given IV
Glucagon IM can be given if no venous access but the above is first line
What is Addison’s disease? what is the cause?
Adrenal insufficiency - low aldosterone, cortisol production from adrenal glands
- Most commonly autoimmune - thus ACTH is high
- In developing countries caused by military TB affecting the adrenal gland.
What are the clinical features of Addison’s disease?
- high ACTH
- hyponatraemia (due to low aldosterone)
- hyperkalaemic metabolic acidosis
- hypoglycaemia
- hypotension (due to low aldosterone)
- hyperpigmentation (due to to high ACTH)
- oesinophilia
What is the formula for working out serum osmolarity?
2na + urea + glucose
How does diabetic amyotrophy present?
- an asymmetrical neuropathy affecting peripheral nerves
- Wasting of proximal leg muscles - quads, hips, buttocks
- loss of reflexes
What is the mechanism of microvascular damage in the diabetes?
Microvascular complications triad:
1. neuropathy
2. nephropathy
3. retinopathy
All are affected by “non enzymatic glycosylation” of the basement membrane
Eyes and nerves are also damaged due to “osmotic damage” caused by high glucose levels
What are the features of Conn’s syndrome
Primary Hyperaldosteronism
- HTN
- hypokalaemia
- hypokalaemic metabolic alkalosis
- renin low
- high aldosterone to renin ratio
Cause: aldosterone secreting adenoma
Congenital adrenal hyperplasia
- caused by the enzyme deficiency so aldosterone and cortisol are not produced in the adrenal gland
21 alpha hydroxyls deficiency is most common deficiency - low aldosterone
- Low cortisol
- Hyperkalaemic metabolic acidosis
- Hypotension
- Increased androgen production due to alternative pathways being used
Ambiguous genitalia in females
Precocious puberty in boys
What are the main causes of hypercalcaemia?
- primary hyperparathyroidism
- malignancy (due to PTH related protein or bone mets)
- myeloma
- paget disease
- Zollinger Ellison syndrome
- Hyperthyroidism can cause increased bone turnover
- Sarcoidosis
- Addison’s disease to increased reabsorption of fluid and electrolytes including calcium in the nephron
- Excessive Vit D or calcium supplements
What is the cause of primary hyperparathyroidism?
80% due to single hyper functioning adenoma
20% are due to diffuse hyperplasia of all 4 glands
Also associated with Men 1 and 2a
