CUSHING'S SYNDROME

Dx of prox. mm. wkness: duck-walking

Causes:

  1. Iatrogenic
  2. Cushing's dis."-Pit. adenoma (70% of non-iatrogenic)
  3. Ectopic ACTH-secreting tumor
  1. Oat cell lung Ca
  2. Carcinoid
  3. Pancreatic islet cell Ca
  4. Medullary thyroid Ca
  5. Pheochromocytoma
  1. Adrenal causes
  1. Adrenal Ca
  2. Adrenal adenoma
  3. Micronodular tumors

Diagnosis:

  1. Dexamethasone suppression test: give a dose of dex late evening and check am cortisol; if it's not low that suggests dx of Cushing's
  2. 24h urine free cortisol
  3. Spot midnight serum cortisol > 7.5 ug/dl was 96% sens and 100% specific for dx of Cushing's in a series of 263 inpatients with an abnormal finding on one of the 2 studies above; the gold standard used was clnical dx with further lab testing, tissue path, and at least 1y of clinical f/u (J. Clin. Endocrin. Metab. 83:1163, 1998--JW)