endocrinology Flashcards
what does the adrenal cortex produce
hormones:
glucocorticoids –> cortisol
mineralcorticoids –> aldosterone
androgens –> testosterone
what does the adrenal medulla produce
adrenaline and noradrenaline under the control of sympathetic nervous system –> secretes into blood stream
what is the function of aldosterone
increases sodium and water resorption
increases potassium and hydrogen excretion into urine
where in the kidney does aldosterone work to increase water resorption
collecting ducts at principal cells and intercalated cells
what is the function of cortisol
stress hormone:
- raises plasma glucose level
- maintains blood pressure - high levels causes an increased BP, low levels decreases your BP
- suppresses the immune system (low b and t cell levels)
- blocks migration of neutrophils into cells so get a rise in serum neut bc blocked from going into cells
- chronic high levels of cortisol causes lipolysis of fat tissues
describe the mechanism of cortisol release
- corticotrophin releasing hormone released from hypothalamus
- causes anterior pituitary to release ACTH (adrenocorticotrophic hormone)
- ACTH acts on the adrenal cortex to stimulate production and release of glucocorticoids (cortisol)
- when level of plasma cortisol is high it has a negitive feedback effect on the hypothalamus and anterior pituitary causing inhibition of ACTH release so therefor less cortisol released
when is serum cortisol the highest
in a morning around 6am
when is serum cortisol lowest
at night just after you go to sleep
why do you give steroids to test for cushings diagnosis
because steroids eg dexamethasone and prednisolone have a similar chemical structure to cortisol so giving the drug should cause negative feedback causing a reduction in cortisol levels
why can people on long term steroids develop diabetes
long term excess glucocorticoid causes peripheral insulin resisitance
why do people on long term steroids develop oteoporosis / osteopenia
because long term high glucocorticoid levels inhibits osteoblasts
name the 3 zones of the adrenal cortex
zona glomerulosa - mineralcorticoids - aldosterone
zona fasciculata - glucocorticoids - cortisol
zona reticularis - androgens - testosterone
(GFR)
which zone of adrenal cortex is aldosterone produced in
zona glomerulosa
which zone of adrenal cortex is cortisol produced in
zona fasciculata (F for fat - cushings - cortisol)
which zone of adrenal cortex is testosterone produced in
zona reticularis
what hormone is increased in cushings disease
cortisol (glucocorticoid)
what can the causes of cushings syndrome be separated into
ACTH dependent
ACTH independent
name 3 ACTH independent causes of cushings disease
- high dose steroids
- cancer
- adrenal hyperplasia
what would be the findings on investigation in ACTH independent cushings syndrome
- high cortisol
- low ACTH due to negitive feedback on pituitary
- overnight dex suppression test –> suppression would happen via negitive feedback so ACTH would be low at 8am
- 48 hour dex suppression test = ACTH would be low at 48 hour mark = suppressed
what drug shouldnt be given in HHS
insulin bc can cause central pontine myelinolysis
bitemporal hemianopia, galactorrhoea and impotence (men) and amenorrhoea (women) - what is the probablye diagnosis
pituitary adenoma (prolactinoma secreting tumour)
what is the first line management of prolactinomas
dopamine agonists!! eg bromocriptine or cabergoline
work by inhibiting prolactin release from pituitary gland
give dopamine agonist even if has severe symptoms eg visual loss
second line is trans sphenoidal removal of tumour - only done for people who cant tolerate the meds
