Cushings Flashcards
difference between cushings syndrome and cushings disease
cushings syndrome - signs + symptoms that develop after prolonged elevation of cortisol
Cushing disease - pituitary adenoma secretes ACTH causing symptoms of cushings
features of cushings
moon face central obesity abdominal strie buffalo hump proximal muscle wasting
HTN, T2DM, cardiac hypertrophy, depression, insomnia, osteoporosis
causes of cushings
exogenous steroids
cushings disease- pituitary adenoma secreting ACTH
adrenal adenoma
paraneoplastic cushings
what is paraneoplastic cushings
when excess ACTH is released from a cancer stimulating cortisol release
- ectopic cushings
most common cause of paraneoplastic cushings
small cell lung cancer
investigation for cushings
dexamethasone suppression test
- initially low dose: if normal cushings can be excluded
- if abnormal: high dose test performed to differentiate causes
how is dexamethasone suppression test performed
patient given dose of dexamethasone at night and their cortisol + ACTH measured in the morning
- intention is to find out if dexamethasone suppresses normal morning spike of cortisol
what dose of dexamethasone is used in
- low dose
- high dose
dexamethasone suppression tests
low dose = 1mg
high dose = 8mg
what is a normal response to low dose dexamethasone test? i.e. no cushings
dexamethasone will suppress the cortisol
what causes of cushings does the high dose dexamethasone suppression test distinguish between
pituitary adenoma
adrenal adenoma
ectopic ACTH
high dose dexamethasone test result: pituitary adenoma
cortisol + ACTH suppressed
high dose dexamethasone test result: adrenal adenoma
cortisol not suppressed, ACTH suppressed
- cortisol production is independent of pituitary
high dose dexamethasone test result: ectopic ACTH
both cortisol + ACTH not suppressed
- ectopic production independent of hypothalamus/pituitary
what test can be used as alternative to low dose dexamethasone test
24 hour urinary free cortisol
- does not indicate underlying cause
scan used to show
- pituitary adenoma
- adrenal tumour
- small cell lung cancer secreting ACTH
pituitary adenoma – MRI brain
adrenal tumour – abdo CT
small cell lung cancer – chest CT
