cush Flashcards
(32 cards)
where is CRH released from?
paraventricular nucleus of hypothalamus
what stimulates ACTH release & from where?
CRH stimulates anterior pituitary gland to release ACTH
name 2 ACTH dependant causes of Cushing’s syndrome
1) Pituitary adenoma - Cushing’s disease
2) Ectopic ACTH release
name 2 ACTH independant causes of Cushing’s syndrome
1) Therapeutic corticosteroid intake
2) Adrenal tumour (adenoma/carcinoma)
1st line investigation suspected Cushing’s syndrome (3)
- 24 hour urinary free cortisol
- midnight cortisol
- low dose dexamethasone suppression test
how is low dose dex suppression test carried out?
1mg dex given at 11pm & serum cortisol measured at 8am
conditions that can cause high cortisol in absence of cushings?
- pregnancy
- depression
- alcohol dependance
- morbid obesity
- poorly controlled DM
what test helps to discriminate between pituitary source & ectopic/adrenal source of Cushing’s syndrome
High dose (8mg) dexamethasone suppression test
high dose dex suppression test & pituitary source –> what is cortisol?
Cortisol is suppressed
high dose dex suppression test & ectopic/adrenal source –> what is cortisol?
no change
clinical blood test result in cushing’s syndrome?
Hypernatraemia, hypokalaemia, metabolic alkalosis
Corticosteroid affect on renal tubules?
- reabsorption of Na
- K+ loss
acid base imbalance seen in Cushing’s syndrome & why?
cellular shifts of K+ & H+ cause metabolic alkalosis
1st line test when establishing a cause of the cushing’s syndrome?
Serum ACTH
9am & midnight
what does a low plasma ACTH level suggest is the cause of Cushings?
ACTH independant cause
what does a non suppressed ACTH level suggest is causing Cushings?
ACTH dependant causes e.g. Cushing’s disease or ectopic ACTH cause
investigation that can help to identify a microscopic pituitary adenoma
Petrosal sinus sampling
low dose dex (1mg) result in cushings sydnrome
raised cortisol
high dose dex (8mg) in ectopic ACTH cause of cushings sydnrome
high ACTH
high cortisol
high dose dex (8mg) in Adrenal tumour
cortisol remains high
ACTH is low - has been suppressed
high dose (8mg) in Cushings disease (pituitary adenoma)
ACTH & cortisol are suppressed
radiological invs for pituitary adenoma
MRI brain
radiological invs for ectopic ACTH production
Chest CT
CXR
radiological invx for ?adrenal tumour
abdominal CT
