Cushing's syndrome Flashcards
What are the physical features of Cushing’s?
Round "moon" face Central obesity Abdominal striae Buffalo hump Proximal limb muscle wasting
What are the effects of high levels of stress hormone in cushings?
hypertension cardiac hypertrophy hyperglycaemia depression insomnia
What are the extra effects of cushings?
osteoporosis
easy bruising and poor skin healing
What are the causes of cushings syndrome?
Exogenous steroids
Cushings disease (pituitary adenoma releasing ACTH)
Adrenal adenoma
Paraneoplastic Cushings
What is paraneoplastic cushings?
when excess ACTH is released from a cancer and stimulates excessive cortisol release. small cell lung cancer is the most common cause
What is the test of choice for diagnosing cushings?
dexamethasone suppression test
Describe the low dose dexamethasone test
a normal reposes is for dexamethasone to suppress the release of cortisol by effecting negative feedback of the hypothalamus and pituitary. When cortisol level is not suppressed this is an abnormal response seen in cushings syndrome
Describe the high dose dexamethasone test
This is performed after an abnormal result on the low dose test
In Cushings disease the pituitary still shows some response to negative feedback
When there is an adrenal adenoma cortisol production is independent from the pituitary. Therefore cortisone is not suppressed but ACTH is due to neg feedback
When there is ectopic ACTH, neither cortisol or SCTH will be suppressed
Cortisol and ACTH levels in pituitary adenomas
Suppressed
Suppressed
Cortisol and ACTH levels in adrenal adenomas
Not suppressed
Suppressed
Describe cortisol and ACTH levels in ectopic ACTH
not suppressed
not suppressed
What is an alternative to the dexamethasone suppression test?
24 hour urinary free cortisol
What other investigations can be carried out for cushings syndrome?
FBV (raised white cells) and electrolytes (K+ may be low if aldosterone is also secreted by an adrenal adenoma)
MRI brain for adrenal adenoma
Chest CT for small cell lung cancer
abdominal CT for adrenal tumours
What are the main treatments of cushings syndrome?
Transphenoidal removal of pituitary adenoma
surgical removal of adrenal tumour
surgical removal of tumour producing ectopic ACTH
IF surgical removal of the cause is not possible another option is to remove both adrenal glands and give the patient replacement steroid hormones for life
