Adrenal glands Flashcards
what are the layers of the adrenal gland structure and what so they produce?
CORTEX
- zona glomerulus : mineralocorticoids like aldosterone SALT.
- zona fasiculata : Glucocorticoids like cortisol SUGAR.
- zona reticularis : glucocorticoids and androgen SEX.
MEDULLA
- chromaffin cells : adrenaline and noradrenaline.
what are some characteristics of steroid hormones?
- synthesised from cholesterol in adrenal glands and gonads.
- lipid soluble.
- binds to nuclear receptor family receptors to modulate gene transcription.
- eg : gluco/mineralocoticoids, androgens, oestrogens, progestins.
how do corticosteroids exert action by regulating gene trasncription?
- diffuse across plasma membrane and binds to glucocorticoid receptor causing dissociation of chaperone proteins.
- receptor ligand complex translocated to nucleus.
- receptor binds to glucocorticoid response element GRE or other transcription factors.
describe aldosterone and its effects.
- mineralocorticoid which is a steroid lipophilic hormone carried with albumin.
- receptors intracellular and regulated gene transcription.
- in nephron promoted NA+/K+ pump expression so reabsorption of Na+ and excretion of K+ influencing water retention, increasing Blood vol and pressure.
RAAS system!!! LOOK OVER SLIDE.
what causes hyperaldosteronism?
- primary defect in adrenal cortex : bilateral idiopathic adrenal hyperplasia, Conn’s syndrome (adenoma), low renin.
- secondary overactive RAAS : renin producing tumour, renal artery stenosis, high renin levels.
how does hyperaldosteronism present and how would you treat?
- signs : high BP, low ventricular hypertrophy, stroke, hypernatraemia, hypokalamia.
- treatment : adenomas removed by surgery, spironolactone which is a mineralocorticoid receptor antagonist.
describe the features and actions of cortisol.
- most abundant corticosteroid counting for 95% of glucocorticoid activity,
- steroid hormone carried in plasma by transcortin.
- negative feedBack to hypothalamus inhibits CRH & ACTH.
- regulates gene transcription, synthesised in response to ACTH.
actions : increased protein breakdown, lipolysis of fat, gluconeogenesis, anti-inflammatory, depression of immune response, resistance to stress by increasing available glucose.
describe briefly the pathway of stress in the hypothalamic-pituitary-adrenal axis.
- stress –> hypothalamus –> CRH –> anterior pituitary –> ACTH –> adrenal cortex –> cortisol –> target tissue.
what are the overall glucocorticoid actions on metabolism?
- increased glucose production.
- breakdown of proteins.
- redistribution of fats in abdomen, buffalo hump, moon face.
what external and endogenous causes of cushing’s syndrome?
and what are the signs?
- external : prescribed glucocorticoids.
- endogenous : cushing’s disease and adenoma secreting ACTH, cortisol producing adrenal tumour (adrenal cushing’s), non-pituitary adrenal tumours producing ACTH like small cell cancer.
- signs : moon face, buffalo hump, abdominal obesity, purple striae, acute weight gain, hyperglycaemia etc.
what is the significance of steroid drugs?
eg: prednisolone, dexamathasone.
- anti-inflammatory and immunomodulatory.
used to treat inflammatory disorders like asthma, inflammatory bowel disease, RA, auto immune diseases. - suppress immunity in organ transplantation.
- side effects : high cortisol effects.
SHOULD BE GRADUALLY REDUCED NOT STOPPED IMMEDIATELY.
what is addison’s disease?
- chronic adrenal insufficiency commonly caused by destructive atrophy from autoimmune response (used to be TB complication).
- presents as postural hypotension, lethargy, weight loss, anorexia, increased skin pigmentation (decreased cortisol causing increased POMC & MSH) hypoglycaemia.
what is an addisonian crisis?
- life threatening emergency due to adrenal insufficiency precipitated by severe stress, salt depravation, infection, trauma, abrupt steroid drug withdrawal.
- symptoms nausea, vomiting, pyrexia, hypotension.
- treatment being fluid replacement, cortisol.
describe importance of androgens.
- DHEA which is an androgen is converted to testosterone in testes pre-pubery release of testosterone alone.
- in females these are converted to oestrogen by other tissue which is the only source after menopause. or purely used to promote libido.
- promotes axillary and pubic hair growth in both sexes.
describe the special structure of the adrenal meduall.
- modified sympathetic ganglion on ANS with chromaffin cells that lack axons but act as postganglionic nerve fibres to release AD & NAD to blood.
LOOK AT SLIDES.
