3 Adrenal Gland Flashcards
what is the pathway in which cortisol is produced?
CRH released by hypothalamus which travels and stimulates anterior pituitary to release ACTH, adrenal gland then stimulated which secretes cortisol
how does cortisol take part in negative feedback?
the cortisol produced acts upon pituitary to stop production of ACTH and hypothalamus to stop CRH
what does ACTH stand for?
adrenocorticotrophin hormone
what is the gene responsible for ACTH production?
POMC gene
what is the transcription factor of the POMC gene?
Tpit
how are different products produced from the POMC gene?
peptides produced from specific peptidase cleavage
how does ACTH act on the adrenal gland?
on the MC2 receptor which is a G protein receptor in the adrenal gland
how might a ACTH deficiency be caused?
mutations in Tpit causing less regulation of POMC gene expression
what are the specific peptidases that cleave the POMC gene?
PC1 and PC2
how is beta endorphin produced from the POMC gene?
POMC cleaved into N-POC and beta lipotropin, the beta lipotropin is then cleaved into gamma lipotropin and beta endorphin
what hormones are produced from cleavage of N-POC?
ACTH and MSH
how is the production of beta endorphin useful in production of ACTH?
produced in a stress response so acts as a pain reliever in fight or flight
what effects does MSH have?
exerts effects through G protein receptors including MC1 receptor in skin to alter pigmentation
how can ACTH production be tested for?
measure cortisol levels, synacthen tests, dexamethasone suppression test
how does the dexamethasone test work?
it is an analogue of cortisol and so can be used to test the function of the negative feedback and test for excess ACTH levels
what does the cortex of the adrenals produce?
glucocorticoids, mineralocorticoids, androgens
what does the medulla of the adrenals produce?
catechalomines
what is an example of a glucocorticoid?
cortisol
what are the functions of glucocorticoids?
increase glycogenolysis and gluconeogenesis, sensitise arterioles to noradrenaline, initiation of diuresis
what is an example of a mineralocorticoid?
aldosterone
what are the functions of aldosterone?
also released with ACTH and causes reabsorption of sodium in distal tubules, alter distribution of sodium and potassium in the body
what do androgens do?
promote formation of secondary sexual hair
what does the zona fasciculate pathway form?
cortisol and corticosterone
what does the zona golmerulosa pathway form?
aldosterone
what does the zona reticular pathway form?
androstenedione
what do all adrenal steroid production pathways come from?
cholesterol
how is aldosterone production regulated?
when renin converts angiotensinogen to angiotensin I and then enzymes convert this to angiotensin II, this acts on adrenals to regulate aldosterone production
what is Addisons disease?
hypofunction of adrenal gland caused by inflammation
what are the causes of Addisons disease?
autoimmune adrenalitis, tuberculosis, adrenalectomy
what are the less common causes of Addisons?
secondary tumour deposits, amyloiditis, adrenal haemorrhage
what are the common clinical features of Addisons?
tiredness, weakness, weight loss, nausea, loss of body hair
what is cushings disease?
hyperfunction of adrenal gland causing excess cortisol
what is andrenogenital syndrome?
excess androgens
what is conns syndrome?
excess aldosterone
what causes conns syndrome?
adrenal adenoma, bilateral hypertrophy of zona glomerulosa cells
what are the clinical features of conns syndrome?
hypertension, muscle weakness, polydipsia and polyuria
what are the causes of Cushings syndrome?
pituitary hyper secretion of ACTH, adrenal adenoma/carcinoma, ectopic secretion of ACTH by tumours
what are the clinical features of Cushing’s syndrome?
truncal obesity, thinning of skin, purple striae, excessive bruising, muscle weakness
what is the cause of cushings disease?
increased ACTH secretion, pituitary insensitive to normal levels of cortisol and so higher levels of cortisol needed in order to have negative feedback effect
what is a secondary hyperaldosteronism?
involves activation of renin
what are the common causes of a secondary hyperaldosteronism?
congestive cardiac failure, cirrhosis of the liver and nephrotic syndrome
