Endocrinology Flashcards
What does the anterior pituitary gland release?
FSH
LH
ACTH (adrenocorticotropic hormone)
TSH
Prolactin
GH
What does the posterior pituitary release?
Oxytoxin
ADH
What are the components of the Thyroid axis?
TRH (from hypothalamus)
TSH
T3/T4 (triiodothyronine / thyroxine)
What are the components of the adrenal axis?
Diurnal variation (peak at early morning)
CRH (corticotrophin release hormone)
ACTH
Cortisol (from adrenal gland - stress hormone)
What are the actions of cortisol in the body?
- Inhibits immune system
- Inhibits bone formation
- Raises blood glucose
- Increases alertness
- Increases metabolism
What are the components of the growth hormone axis?
GHRH (somatostatin inhibits, ghrelin promotes)
GH
Insulin-like growth factor (IGF-1) from liver
What is the action of growth hormone?
- Stimulates muscle growth
- Increases bone density
- Stimulates cell regeneration and reproduction
- Stimulates growth of internal organs
When is PTH released?
Low serum calcium and low magnesium (and high serum phosphate) to increase calcium resorption
What does PTH do?
Increases activity and number of osteoclasts in the bone, causing resorption into the blood, increasing serum calcium.
Stimulates an increase in calcium reabsoption in the kidneys
What is the additional function of PTH?
Stimulates the kidneys to convert vitamin D3 into calcitriol (active form of vit D) which promotes calcium absoption from food in small intestine
Where is Renin secreted from?
Juxtaglomerular cells in the afferent and efferent arterioles in kidbey (sense blood pressure - secrete less if BP is high)
What is the role of renin?
Enzyme converts angiotensinogen (from liver) into angiotension I
What are the two actions of angiotention II?
Acts on blood vessels to vasoconstrict and stimulates the release of aldosterone form adrenal glands
What does aldosterone result in?
Acts on nephrons to increase sodium reabsorption in distal tubules, potassium secretion in distal tubules and hydrogen secretion from collecting ducts
Hypernatraemia
Hypokalaemia
What is Cushing’s syndrome vs Cushing’s disease?
Syndrome = signs & symptoms after prolonged elevated cortisol
Disease = pituitary adenoma secreting excessive ACTH
What is the causality between Cushings disease and Cushing syndrome?
Disease can cause syndrome but syndrome isnt always caused by disease
What are the features of Cushing’s syndrome?
Moon face
Central obesity
Abdo striae
Buffalo hump
Proximal limb muscle wasting
Hypertension
Cardiac hypertrophy
Hyperglycaemia
Insomnia
Osteoporosis
Easy brusing
What are the other effects of high level of stress hormone?
Hypertension
Cardiac hypertrophy
Hyperglycaemia (type 2 diabetes)
Depression
Insomnia
Osteoporosis
Easy bruising / poor skin healing
What are some causes of Cushing’s syndrome?
- Exogenuos steroids
- Cushings Disease
- Adrenal adenoma (not pituitary)
- Paraneoplastic cushings
What is the most common cause of paraneoplastic Cushings?
SCLC (excess ACTH from cancer)
What is the choice of test for Cushing’s?
Dexamethasone Suppression Test
How does the dexamethasone suppression test work?
Patient is given low dose of dexamethosone (synthetic glucocorticoid steroid) at night and cortisol/ACTH is measured in the morning to see if its been suppressed
In the high dose Dexamathasone Suppression test (8mg vs 1mg - done if low dose test abnormal) what is the difference between Cushing’s Disease and an Adrenal Adenoma?
Cushing’s disease still shows some response to negative feedback whereas Adrenal Adenomas do not (however ACTH is supressed)
In ectopic ACTH neither cortisol or ACTH will be supressed
Complete the following:
What is the other investigation for Cushing’s?
24 hour urinary free cortisol (doesn’t indicate underlying cause and cumbersome)
What is the imaging of choice for Cushing’s syndrome?
What will blood tests show?
MRI brain for pituitary adenomas
Chest CT for small cell lung cancer
Abdo CT for adrenal tumours
Bloods
FBC (raised WCC) and electrolytes (potassium may be low if aldosterone also secreted by adrenal adenoma)
What is the treatment of Cushing’s?
Trans-sphenoidal surgery for pituitary adenoma
Surgical removal of adrenal tumour / tumour producing ectopic ACTH
If surgical removal of cause not possible then can remove both adrenal glands and give replacement steroids for life
What hormones are particularily lacking in adrenal insufficiency?
Cortisol and aldosterone
What is Addison’s disease?
Specific condition where the adrenal glands have been damaged resulting in a reduction of cortisol and aldosterone (mainly autoimmune cause)
Aka primary adrenal insufficiency
What is secondary adrenal insufficiency commonly due to?
Inadequate ACTH resulting in low cortisol
E.g. from sugery to remove pituitary tumour, infection, loss of blood, radiotherapy
What is Sheehan’s syndrome?
Massive blood loss during childbirth leading to pituitary gland necrosis (causes secondary adrenal insufficiency)
What is teritary adrenal insufficiency?
Inadequate CRH released by the hypothalamus usually the result of the patient being on long term steroids (more than 3 weeks) causing suppression of the hypothalamus.
When steroids are stopped then hypothalamus doesn’t ‘wake up’ quick enough, so steroids shouldnt be stopped abruptly
What are some symptoms of adrenal insufficiency?
- Fatigue
- Nausea
- Cramps
- Abdo pain
- Reduced libido
What are some signs of adrenal insufficiency?
Bronze skin due to ACTH stimulating melanocytes to produce melanin
Postural hypotension
What are some investigations for adrenal insufficiency?
Hyponatraemia (key clue)
Hyperkalaemia
Early morning cortisol (often falsely normal)
SHORT SYNACTHEN TEST (for diagnosis)
What antibodies are present for autoimmune Addison’s?
Adrenal cortex antibodies and 21-hydroxylase antibodies
What imaging can be used for Adrenal insufficency?
CT/MRI for adrenal tumour, haemorrhage
MRI pituitary for further info about pituitary
What are the ACTH levels in primary adrenal failure and secondary adrenal failure?
Primary = ACTH high
Secondary = ACTH low
What is the short syntacthen test ?
Give patient synacthen (synthetic ACTH) in morning
Blood cortisol measured at baseline, 30 mins, 60 mins after.
Should rise, if not (at least double) then primary adrenal insufficiency (Addison’s disease)
What is the treatment for adrenal insufficiency?
Hydrocortisone is a glucocorticoid to replace cortidol
Fludrocortisone is a mineralcorticoid to replace aldosterone
What are patients with adrenal insifficiency given in addition?
Steroid card and emergency ID tag (indicate they are dependent on steroids)
Doses doubles during acute illness
How do patients with Addisonian crisis present (acute presentation of severe addisons)?
- Reduced consciousness
- Hypotension
- Hypoglycaemia, hyponatraemia, hyperkalaemia
When can an Addison’s crisis occur?
Long term steroids stopped abruptly
Infection
Trauma
Other acute illness
What are the management options for a patient with an Addisonian Crisis?
- Intensive monitoring if unwell
- Parenteral steroids (IV hydrocortisone 100mg stat then 100mg every 6 hours)
- IV fluid resuscitation
- Correct hypoglycaemia
- Monitor U&Es
What are the TFTs in hyperthyroidism?
TSH is suppressed so low TSH, apart from in pituitary adenoma which secretes TSH
How are the TFTs in hypothyroidism?
TSH is high (exception is pituitary/hypothamic cause when TSH will be low)
Label the following:
What antibodies are present in Grave’s and Hashimoto’s disease?
anti-TPO (antithyroid peroxidase) antibodies
anti-thyroglobulin antibodies (limited use as present in normal individuals)
What antibodies are present in Grave’s disease?
TSH receptor antibodies
What imaging is available for thyroid problems?
Thyroid ultrasound - diagnose thyroid nodules, and for biopsy guide (distinguish between cystic and solid nodules)
Radioisotope scans - for hyperthyroidism and thyroid cancers (diffuse uptake of iodine in Graves, focal is adenomas/toxic multinodular goitre, ‘cold’ aka abnormally low is thyroid cancer) gamma camera is used to detect gamma rays from radioactive iodine
What is Graves’ disease?
Autoimmune condition where TSH receptor antibodies (mimic TSH) cause a primary hyperthyroidism
What is toxic multinodular goitre (Plummer’s disease)?
Nodules develop on the gland acting independently of the normal feedback system and continuously produce excessive thyroid hormone
When is exopthalmos seen?
Grave’s disease
What is pretibial myxoedema?
Specific to Grave’s disease where there are deposits of mucin under the skin and on the anterior aspect of the leg - discoloured, wavy, oedematous appearance of the skin over this area (reaction to the TSH receptor antibodies)
What are some causes of hyperthyroid?
Grave’s disease
Toxic multinodular goitre
Solitary toxic thryoid nodule
Thyroiditis (e.g. De Quervain’s, Hashimoto’s, postpartum and drug-induced thyroiditis)
What are some universal features of hyperthyroidism?
- Anxiety and irritabilty
- Sweating and heat intolerance
- Tachycardia
- Weight loss
- Fatigue
- Losse stools
- Sexual dysfunction
What are some unique features of Grave’s disease?
- Diffuse Goitre (without nodules)
- Graves eye disease
- Exopthalmos
- Myxoedema
What are some unique features of toxic multinodular goitre?
- Goitre with firm nodules
- Most patients >50
- Second most common form of thyrotoxicosis (after Graves’)
What is a single abnomal thyroid nodule called?
Adenoma (benign - treated with surgical removal)
What is De Quervain’s Thyroiditis?
Viral infection with fever, neck pain and tenderness, dysphagia and features of hyperthyroidism.
Hyperthyroid phase followed by a hypothyroid phase as the TSH levels fall due to negative
Self limiting condition and supportive treatment is with NSAIDs for pain and beta-blockers for symptoms
What is a Thyroid Storm?
Rare presentation of hyperthyroidism‘thyrotoxicosis crisis’
Severe presentation of hyperthyroidism with pyrexia, tachycardia and delerium (requires admission)
What is the first line antithyroid drug?
Carbimazole - remission is usually achieved in 18 months of treatment
Titration block = careful titration for normal levels
Block and replace = blocks all production and patient take levothyroxine
What are the other treatments for hyperthyroidism?
Propylthiouracil - second line used in similar way to carbimazole (small risk of severe hepatic reaction)
Radioactive iodine treatment - (drinking single dose of radioactive iodine) radiation destroys the thyroid cells - can be left hypothyroid after and require levothyroxine replacement
Beta blockers (blocks adrenaline symptoms - propanolol is non selective so works everywhere)
Surgery (thyroidectomy) - requires levothyroxine for life
What are the ‘rules’ for radioactive iodine treatment?
- Patient must not be pregnant to allowed to get pregnancy in 6 months
- No close contact with children/pregnant women 3 weeks after
- Limit contact with anyone for several days after
What are some causes of hypothyroidism?
Hashimoto’s Thyroititis (anti-TPO and antithyroglobulin antibodies - with goitre followed by atrophy of thyroid gland)
Iodine deficiency
Secondary to treatment of hyperthyroidism (carbimazole, propylthiouracil, radioactive iodine, thyroid surgery)
What medications can inhibit the production of thyroid hormones?
Lithium
Amiodarone
What are some central causes (secondary) hypothyroidism?
Pituitary gland fails to produce enough TSH (associated with lack of ACTH) - hypopituitarism:
- Tumours
- Infection
- Vascular (e.g. Sheehan syndrome)
- Radiation
How do patients with hypothyroidism present?
- Weight gain
- Fatigue
- Dry skin
- Coarse hair
- Fluid retention (oedema, ascites)
- Heavy / irregular periods
- Constipation
What is the management of hypothyroidism?
Levothyroxine (synthetic T4) which is metabolised to T3 in the body
Initially measure monthly until stable then less frequently until symptomatic
What does the body want to keep blood glucose between?
4.4 and 6.1
Where is Insulin made?
Beta cells in the Islets of Langerhans in the pancreas
How does insulin reduce blood sugar?
Causes cells in the body to absorb glucose and causes formation of glycogen stores (in muscle and liver)
Where it glucagon made?
Alpha cells in the Islets of Langerhans in the pancreas
What does Glycogen do?
Tells the liver to break down stored glycogen into glucose (glycogenolysis)
Also promotes gluconeogenesis