Cushing's Syndrome

Question 1

What is Cushing’s syndrome?

Answer 1

High levels of glucocorticoids in the body

Question 2

What is the primary glucocorticoid produced by the body?

Answer 2

Cortisol

Question 3

What is Cushing’s disease?

Answer 3

Cushing’s syndrome as a cause of a pituitary adenoma - the pituitary adenoma secretes excess ACTH that results in excessive cortisol

Question 4

What is the most common cause of Cushing’s disease?

Answer 4

Cushing’s disease

Question 5

What are the other causes of Cushing’s syndrome?

Answer 5

Ectopic ACTH production e.g small cell lung cancer
Steroids
Adrenal adenoma
Adrenal carcinoma

Question 6

What is pseudo-Cushing’s?

Answer 6

Conditions that mimic Cushing’s - often caused by severe depression or alcohol excess

Question 7

What test can differentiate between Cushing’s and pseudo-Cushing’s

Answer 7

Insulin stress test - in patients with psuedo-Cushing’s, cortisol levels will rise in response to hypoglycaemia

Question 8

What are the features of Cushing’s syndrome?

Answer 8

Round face
Central obesity
Abdominal striae
Buffalo hump
Proximal limb muscle wasting
Hirsutism
Easy bruising
Hyperpigmentation of skin

Question 9

What metabolic conditions are associated with Cushing’s syndrome?

Answer 9

Hypertension
Type 2 diabetes
Dyslipidaemia
Osteoporosis

Question 10

What investigation is used to diagnose Cushing’s?

Answer 10

Dexamethasone suppression test

Question 11

What are the three types of dexamethasone suppression test and what are they used for?

Answer 11

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

Question 12

What is a normal dexamethasone suppression test?

Answer 12

Cortisol is suppressed

Question 13

What is the action of dexamethasone on cortisol?

Answer 13

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

Question 14

What other investigations may be useful in diagnosis of Cushing’s syndrome?

Answer 14

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

Question 15

What is the treatment of Cushing’s disease?

Answer 15

Treatment of underlying problem:
- Trans-sphenoidal resection of pituitary adenoma
- Surgical removal of adrenal tumour
- Surgical removal of ectopic ACTH tumour