Cushing's Syndrome Flashcards
What is Cushing’s syndrome?
High levels of glucocorticoids in the body
What is the primary glucocorticoid produced by the body?
Cortisol
What is Cushing’s disease?
Cushing’s syndrome as a cause of a pituitary adenoma - the pituitary adenoma secretes excess ACTH that results in excessive cortisol
What is the most common cause of Cushing’s syndrome?
Cushing’s disease - ACTH secretion from a pituitary adenoma
What are the other causes of Cushing’s syndrome?
Ectopic ACTH production e.g small cell lung cancer
Steroids
Adrenal adenoma
Adrenal carcinoma
What is pseudo-Cushing’s?
Conditions that mimic Cushing’s - often caused by severe depression or alcohol excess
What test can differentiate between Cushing’s and pseudo-Cushing’s
Insulin stress test - in patients with psuedo-Cushing’s, cortisol levels will rise in response to hypoglycaemia
What are the features of Cushing’s syndrome?
Round face
Central obesity
Abdominal striae
Buffalo hump
Proximal limb muscle wasting
Hirsutism
Easy bruising
Hyperpigmentation of skin
Mood changes
Menstrual irregularity
Reduced libido
What metabolic conditions are associated with Cushing’s syndrome?
Hypertension
Type 2 diabetes
Dyslipidaemia
Osteoporosis
What investigation is used to diagnose Cushing’s?
Dexamethasone suppression test
What are the three types of dexamethasone suppression test and what are they used for?
Low dose overnight test - used as a screening test to exclude Cushing’s
Low dose 48-hour test - used in suspected Cushing’s
High dose 48-hour test - used to determine the cause in patients with confirmed Cushing’s syndrome
What is a normal dexamethasone suppression test?
Cortisol is suppressed
What is the action of dexamethasone on cortisol?
Dexamethasone negatively feeds back to the hypothalamus - this reduced corticotropin-releasing hormone output, which reduced ACTH output
Reduced ACTH results in a low cortisol level
What other investigations may be useful in diagnosis of Cushing’s syndrome?
24 hour urinary free cortisol
FBC - high white cells
U&Es
MRI brain for pituitary adenoma
CT chest for small cell lung cancer
CT abdomen for adrenal tumours
What is the treatment of Cushing’s disease?
Treatment of underlying problem:
- Trans-sphenoidal resection of pituitary adenoma
- Surgical removal of adrenal tumour
- Surgical removal of ectopic ACTH tumour
