Cushing's Syndrome

Question 0

Causes of Cushing’s syndrome:

Answer 0

• Exogenous steroids
• Pituitary adenoma (Cushing’s DISEASE)
• Adrenal adenoma or carcinoma
• Ectopic ACTH syndrome (wasting due to carcinoma, pigmentation, hypokalaemia)

Question 1

Clinical Features (SWEDISH)

Answer 1

S: ​spinal tenderness
W​: weight, central obesity
E: ​easy bruising
D: ​diabetes
I: ​interscapular fat pat
S: ​striae
H​: hypertension

Question 2

Screening for hypercortisolaemia

Answer 2

• 24 hour urinary free cortisol
• Loss of diurnal rhythm (should be high in am & low in pm Cushing’s high am & pm)
• Low dose dexamethasone test: no suppression of endogenous cortisol

Question 3

To distinguish adrenal from pituitary disease

Answer 3

• ACTH levels are high in Cushing’s disease (pituitary)
• ACTH levels are low (suppressed) in adrenal Cushing’s syndrome
• But the ACTH assay is tricky (degraded within minutes of venepuncture)
• High dose dexamethasone suppresses cortisol levels in Cushing’s disease as the high levels of pituitary ACTH can be partially suppressed by this potent steroid
• High dose dexamethasone does not suppress cortisol levels in adrenal Cushing’s as the production of cortisol is not ACTH dependent