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Ex-USMLE Forums Staff
753 Posts
Hypercortisolism has four major causes

  • Cushing's Disease (Pituitary adenoma)
  • Ectopic ACTH
  • Adrenal adenoma
  • Iatrogenic (Steroids therapy)

They all present with similar signs and symptoms and can be differentiated using the high dose dexamethasone suppression test.

If by mistake you do bilateral adrenalectomy thinking that's it's adrenal cause of cushing while in fact the patient is having pituitary adenoma, this will result in Nelson syndrome.

They will have even more ACTH production (as you removed the negative feedback from adrenal cortisol) and hence more hyperpigmentation.

Nelson syndrome has become very rare in US and it's unlikely to be tested in USMLE.
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