ENDO 128 Gen Endocrine Flashcards
What hormones are secreted from the Thyroid Gland?
T3 & T4
Calcitonin
Where are the parathyroid glands and what do the secrete?
4 glands that sit on the thyroid, secretes PTH
What hormones are released from the adrenal medulla?
Adrenaline and Noradrenaline
What stimulates production and release of T3 and T4 and where is it secreted from?
TSH from the anterior pituitary
What are the actions of TSH?
Increase iodine uptake by the thyroid, stimulates T3 and T4 production, stimulates thyroid growth
What is TSH release stimulated by and controlled by?
Stimulated by TRH from hypothalamus and controlled by negative feedback of T3 and T4 levels
Name some general actions of thyroid hormones
Increases basal metabolic rate: 0xygen use and heat production
Stimulates protein degradation/production
Potentiate insulin effects: glycogenolysis, glucose use
CVS: increase CO, HR, force and syst BP
vasodilatation so decrease diastolic BP
What is the function of Calcitonin?
To prevent hypercalcaemia by inhibiting osteoclasts in bone
What hormone stimulates the release of cortisol from the adrenal gland?
ACTH from anterior pituitary
What does CRH do?
Stimulate ACTH release from anterior pituitary
What is the disease of Cortisol insufficiency?
Addison’s Disease
What is the disease of excess cortisol?
Cushing’s syndrome
Where are adrenaline and noradrenaline stored?
In chromaffin cells in the adrenal medulla
What is phaecromocytoma?
Tumour of the adrenal medulla causing constant secretion of catecholamines
What are some of the signs and symptoms of phaecromocytoma?
Anxiety, forceful heartbeat, hypertension and tremor
What is the function of aldosterone and where is it released from?
Released from the adrenal cortex an acts to regulate sodium and fluid volume
What is Conn’s syndrome?
hyperaldosteronism - excess sodium and water retention therefore increasing blood pressure
What are some causes of hyperthyroidism?
Grave’s disease - autoantibody that stimulates thyroid release
Pituitary adenoma releasing TSH
Thyroid follicular cell tumour
Name some of the clinical presentations of hyperthyroidism
weight loss despite increased appetite, increased resting heart rate, bounding pulse, heat intolerance, eye protrusion, atrial fibrillation
What are some causes of hypothyroidism?
Hashimoto’s thyroiditis - an organ speific autoimmune disease against thyroid epithelial cells
Pituitary hypofunction -lack of TSH (non producing pituitary adenoma)
Thyroid hormone resistance
Name some clinical presentations of hypothyroidism
myxodema (thickening and swelling of the skin), tiredness, lethargy, weight gain, slow mental state, hypothermia and constipation
Describe some of the mechanisms of Cushing’s syndrome
Pituitary adenoma - produces excess ACTH = Cushing’s Disease
Adrenal cortex adenoma
Excess ACTH or glucocorticoid administration
Briefly describe the clinical features of Cushing’s syndrome
Central obesity, depression, hirsutism, bruising, thick skin, striae
How would you investigate suspected Cushing’s syndrome?
- 24 hour urinary free cortisol
- 9am cortisol level
- 48hour low dose dexamethasone test
- High dose dexamethasone test
What would lack of cortisol suppression of a 48 hour low dose dexamethasone test indicate?
Cushing’s syndrome
What would suppression and non-suppression of cortisol indicate in a high dose dexamethasone test?
Suppression: pituitary dependant tumour
Failure: ectopic source of ACTH or adrenal tumour
Describe the clinical features of an Addisonian crisis
Hypotension
Hyponatraemia, hyokalaemia, hypoglycaemia and dehydration
How would you investigate Suspected Addison’s
Short ACTH stimulation test: absent or impaired cortisol response
Electrolytes and urea
Adrenal auto-antibodies
9hour plasma ACTH level
What response would you expect to see in a 9 hour plasma ACTH test for Addison’s
High ACTH with low/normal cortisol = confirmed primary hypoadrenalism
What are some of the causes of Hypercalcaemia?
Excessive PTH secretion
Malignancy
Excess Vitamin D
Drugs e.g. thiazide diuretics, lithium, vitamin A
What are some fo the clinical features of hypercalcaemia?
Stones (renal and billiary); Bones (pain); Groans (abdominal pain, nausea and vomiting); Thrones (polyuria); Psychic moans (depression, coma)
Possible arrhythmias
What are some causes of hypocalcaemia
Increased phosphate levels (CKD); hypoparathyroidism, vitamin D deficiency, PTH resistance, Drugs, Acute pancreatitis, Low plasma albumin
What are some of the clinical features of hypocalcaemia
Neuromuscular irritability: parasthesia, circumoral numbness, cramps, anxiety and tetany
Chvostek’s sign: tapping on facial nerve causes ipsilateral facial muscles to twitch
Trousseau’s sign: When inflating BP cuff above systolic for 3 minutes induces tetanic spasm of fingers and wrist
How would you investigate hypocalcaemia?
Serum and urine creatinine, PTH levels, PTH antibodies, Vitamin D and magnesium levels
How might an androgen deficiency present in an adult?
Small/absent testes, gynaecomastia, sexual dysfunction, small prostate, reduced hair growth
What is PTH released in response to?
falling plasma calcium
How does PTH work?
By increasing loss of phosphate
Increasing calcium reabsorption
Increasing metabolism to active Vitamin D
Stimulates calcium flux from bone by activating osteoclasts
What does Vitamin D do?
increases whole body calcium
increases uptake of calcium in gut
Name some actions of cortisol (glucocorticoids)
Carbohydrate, protein and lipid metabolism (glucose production)
Increases vascular tone and permeability
Sodium and potassium retention
immunosuppressive
