What is the action of metyrapone?
Inhibits 11beta-hydroxylase; steroid synthesis in zona fasciculata and reticularis is arrested at 11-deoxycortisol level -> no negative feedback effect on hypothalamus/pit. gland
What are the uses of metyrapone?
Cortisol synth blocked, ACTH secretion increased and plasma deoxycortisol increased; Control of Cushing's syndrome before procedure (adjusting oral dose to cortisol levels in serum, improving patient's symptoms and promotes better post-op recovery; control of Cushing's symptoms after radiotherapy
What are the unwanted actions of metyrapone?
Hypertension on long-term admin; hirsuitism (due to build up of precursors which are shuffled into the androgen arm of synthesis)
What is the use of Ketoconazole?
Main use as anti-fungal agent, withdrawn due to risk of hepatotoxicity; at high conc, inhibits steroidogenesis; treatment and control of symptoms prior to surgery and are orally active
What is the method of action of ketoconazole?
Blocks multiple steps inc. cortisol synthesis
What are the unwanted actions of ketoconazole?
Liver damage -> possible fatal; monitor liver function weekly, clinically and biochemically
What are the uses of spironolactone?
Primary hyperaldosteronism (conn's syndrome)
What is the mechanism of action of spironolactone?
Converted to several active metabolites inc. canrenone and competitive antagonist of MR; blocks Na reab and K excretion in kidney tubules
What are the pharmacokinetics of spironolactone?
Orally active, highly protein bound and metabolised in liver
What are the unwanted actions of spironolactone?
Menstrual irregularities (+progesterone receptor); gynaecomastia (androgen receptor antagonist)
What is epleronone?
Mineralocorticoid receptor antagonist ithe similar affinity as spironolacton; less binding to androgen and progesterone receptors compared to spironolactone
What are the key features and symptoms of Cushing's syndrome?
Too much cortisol, centripetal obesity, moon face and buffalo hump, proximal myopathy, hypertension and hypokalaemia, red striae, thin skin, bruising, osteoporosis, diabetes
What are the causes of Cushing's syndrome?
Taking too many steroids, pit dependent Cushing's disease, ectopic ACTH from lung cancer, adrenal adenoma secreting cortisol
What investigations are carried out to determine cause of Cushing's?
24h urine collection for urinary free cortisol, blood diurnal cortisol levels (need to check when asleep as that's when they should be at the lowest), low dose dexamethasone (given every 6hrs reducing pit cortisol to 0 if normal but then if failure to suppress dexamethosone occurs then any cause of Cushing's works)
How do you treat Cushing's (surgical and medical)?
Enzyme inhibitors, receptor blocking drugs, pit surgery (transphenoidal hypophysectomy), bilateral adrenalectomy, unilateral adrenalectomy for adrenal mass; metyrapone, ketoconazole
What are phaeochromocytomas?
Tumours of adrenal medulla which secrete catecholamines (A or NA)
What are the clinical features of phaeo?
Severe hypertension in young people which can cause MI or stroke, episodic severe hypertension after abdominal palpation, high adrenaline can cause ventricular fibrillation and death
How do you manage phaeo?
Eventually need surgery, but patient needs careful prep as anaesthetic can precipitate a hypertensive crisis; alpha blockade (1st therapeutic), IV fluid as alpha blockade commences, beta blockade added to prevent tachycardia
How do you diagnose Cushing's?
Basal cortisol (9am) of 800 nM and at end of low dose dexamethasone suppression test: 680 nM
What is Conn's syndrome with biochemical symptoms?
Benign adrenal cortical tumour (zona glomerulosa), aldosterone in excess, hypertension, hypokalaemia
How do you diagnose Conn's syndrome?
Primary hyperaldosteronism -> RAS should be suppressed (excludes 2ry hyperaldosteronism)
How do you treat Conn's syndrome?
Aldosterone receptor antagonist -> spironolactone or surgery to remove adenome; if bilateral adrenal hyperplasia then stay on spironolactone
What are some key facts of phaeochromocytoma?
10% extra-adrenal (symp chain), 10% malignant, 10% bilateral
What are the pathways to make a mineralocorticoid, glucocorticoid and steroid hormones from cholesterol?
NB: main source of sex steroids is in the gonads
What are the 2 general causes of adrenocortical failure?
Adrenal glands destroyed and enzymes in the steroid synthetic pathway not working
What are the names of the causes of adrenocortical failure?
Tuberculous Addison's disease (commonest worldwide), autoimmune Addison's disease (UK commonest), congenital adrenal hyperplasia
What are the consequences of adrenocortical failure?
Fall in BP, loss of salt in urine, increased plasma potassium, fall in glucose due to glucocorticoid deficiency, high ACTH resulting in increased pigmentation, eventual death due to severe hypotension
What is POMC and where is it synthesised?
Pro-opio melanocortin and is synthesised in pit, broken down to ACTH and MSH (causes melanocytes to produce melanin which causes the increased pigmentation in Addison's patients) and endorphins and enkephalins and other peptides
What are the tests for Addison's?
9am cortisol = low, ACTH = high -> short syn"ACTH"en test, give 250 micrograms syncathen IM and measure cortisol response
What are a typical Addison's patient's cortisol before and after synacthen?
Cortisol 9am = 100 (270-900) -> after IM syncathen, cortisol at 9.30 = 150 (>600) -> very little rise in cortisol as adrenal glands are destroyed so cannot produce any more cortisol