Cushing's syndrome Flashcards
Cushing’s syndrome
The signs and symptoms that develop after prolonged abnormal elevation of cortisol
Cushing’s disease
The specific disease where a pituitary adenoma secretes excessive ACTH
Cushing syndrome body features
Round ‘moon’ face
Central obesity
Abdominal striae
Buffalo hump
Proximal limb muscle wasting
Cushing’s syndrome stress hormone features
Hypertension
Cardiac hypertrophy
Hyperglycaemia
Depression
Insomnia
Causes of Cushing’s syndrome
Exogenous steroids
Cushing’s disease
Adrenal adenoma
Paraneoplastic Cushing’s
Paraneoplastic Cushing’s
Excessive ACTH released from a cancer and stimulates excessive cortisol release
Small cell lung cancer the most common cause
Test of choice for diagnosis
Dexamethasone suppression test
Dexamethasone suppression test
Give patient low dose test, if that’s normal Cushing’s can be excluded
If low dose abnormal then high dose performed
Take dexamethasone at night and measure cortisol and ACTH in the morning
Intention of dexamethasone test
To find out if dexamethasone suppresses their normal morning spike of cortisol
Low dose dexamethasone test
Normal response to suppress the release of cortisol
Hypothalamus reduces CRH ouput, pituitary reduces ACTH output, results in lower cortisol
When cortisol level not suppressed this is the abnormal result seen in Cushing’s syndrome
High dose dexamethasone test
In Cushing’s disease pituitary still show some response to negative feedback and 8mg dexamethasone not enough to suppress cortisol
When adrenal adenoma, cortisol production independent from pituitary so cortisone not suppressed, however ACTH is suppressed
When ectopic ACTH this is independent from hypothalamus or pituitary
Pituitary adenoma high dose suppression test
Cortisol suppressed
ACTH suppressed
Adrenal adenoma high dose suppression test
Cortisol not suppressed
ACTH suppressed
Ectopic ACTH high dose suppression test
Cortisol not suppressed
ACTH not suppressed
Other investigations
24-hour urinary free cortisol (doesn’t indicate underlying cause)
FBC- raised WCC
U&Es- potassium may be low if aldosterone also secreted by adrenal adenoma
MRI brain for pituitary adenoma
Chest CT for small cell lung cancer
Abdominal CT for adrenal tumours
