Cushing’s syndrome

• Facts:
  Elevated serum ACTH
  1) Cushing's disease (pituitary adenoma)
  2) Ectopic ACTH (small cell lung CA, pancreatic CA, neuroendocrine tumors, bronchial carcinoids)
  
  Low serum ACTH
  1) Exogenous steroid administration
  2) Bilateral adrenal hyperplasia
  3) Adrenal adenoma
• History / PE:
  Hypertension
  Central obesity (DM II), hypergylcemia, glycosuria
  Thin skin w/ purple striae
  Hirsuitism
  Moon facies, buffalo hump
• Diagnosis:
  Elevated 24-hour free urine cortisol
  
  Positive overnight low-dose dexamethasone suppression test (helps differentiate between Cushing's disease and ectopic ACTH)
  
  Hypernatremia , hypokalemia
  
• Notes:
  In ectopic ACTH Cushing's syndrome, see rapid development of symptoms and can diagnose when serum cortisol and 24hr urine cortisol levels are NOT suppressed following administration of high dose dexamethasone