session 10-disorders of adrenal cortex Flashcards
why can ACTH stimulate increased pigmentation when present in excess and what disease causes it to be present in excess?
POMC is post translated to form ACTH
MSH sequence is contained within ACTH sequence giving ACTH some MSH like activity when in excess
large acth means no cortisol due to no neg feedback. Low cortisol=addisons
what 3 things can be produced from the post translational processing of POMC?
ACTH, alpha-MSH and endorphins
what is the difference between cushings syndrome and disease?
cushings disease= high cortisol levels from a tumour stemming from the ant pituitary gland
cushings syndrome=exogenous–>overuse of medication
endogenous–>ectopic secretion of ACTH (e.g. lung carcinoma)
–>adrenal cortex tumour
Describe the effects of dexamethazone supression test (synthetic hormone…)
-synthetic cortisol
Cushings disease:
-low dose…no effect on pituitary tumour as tumour is pretty insensitive
-high dose…some sensitivity to dexamethazone and so the increased cortisol will lower ACTH production and thus cortisol lowered(suppressed)=cush disease
Cushing syndrome:
- high or low dose of dexa=high cortisol (i.e. not supressed), low ACTH=adrenal tumour
- high or low dose of dexa=high cortisol (not supressed), high ACTH=ectopic ACTH tumour
How do steroids work on a cellular level?
steroids are hydrophobic so can pass through membrane and act on receptors within a cell. can bind to nuclear DNA. Some hormone receptors have similar sequence structure and so sometimes cortisol for example, may be able to bind to androgens and mineralocorticoids
Give 5 clinical effects of cushings/excess cortisol secretion
- increased cortisol action (e.g. muscle proteolysis, hepatic gluconeogenesis)=wasting of proximal muscles
- increased lipogenesis=moon shaped face and weight gain (buffalo hump and distended abdomen)
- purple striae due to protein breakdown and easy bruising
- anti-inflammatory/allergic response=increase infection and acne
- back pain and ribs collapse due to osteoporosis
- mineralocorticoids affected by cortisol and so increased hypertension due to sodium and thus fluid retention (oedema)
what effect does synthetic cortisol have on the body?
-increases cortisol levels and so neg feedback occurs, reducing ACTH and CTH….THUS decreasing cortisol overall
what do they call it when hyperglycaemia occurs due to high levels of cortisol and associated also is polyuria and polydipsia?
steroid diabetes
Too little cortisol causes autoimmune destruction of adrenal gland so also affects mineralocorticoids. In exacerbated conditions such as trauma or infection what can this lead to?
addisonian crisis leadind to:
- nausea
- vomiting
- extreme dehydration
- hypotension
- confusion
- fever
how do you treat an addisonian crisis?
intra venous cortisol and fluid replacement (dextrose in normal saline)
Give 5 symptoms of addison’s disease?
- hypotension
- weight loss
- dehydration
- nausea
- tiredness
- muscle weakness
- increased pigmentation (build up of ACTH and thus MSH activity)
- hypoglycaemia
- vitiligo (white patches on skin)
- abdomen pain
what is the synacthen test?
synthetic ACTH
should increase plasma cortisol…if it doesn’t, then Addison’s (primary)
If cortisol is normal (adrenal gland is normal) and there is hypoactivity, it is secondary
What causes dehydration and hypotension in Addisons? (Opposite for cushings)
- deficiency of mineralocorticoids
- LOW cortisol so LOW Na+ (hyponatremia) and high K+ (hyperkalemia)
- excess water lost
How can you detect secondary adrenal failure?
Insulin stress test
- induce hypoglycaemia by giving insulin
- initiates stress pathway and so ACTH and thus cortisol should rise in levels
- if pituitary not working, ACTH will not rise or cortisol
How to manage cushings/hyperactivity (give three)
- control with drugs
- removal of tumour via surgery
- remove adrenal gland if ACTH dependent cushings (I.e. Ectopic ACTH tumour or cushings disease)
