Perils and pitfalls in the diagnosis of Cushing's syndrome.

SPONTANEOUS CUSHING'S SYNDROME may be corticotropin-dependent due to either pituitary or ectopic hypersecretion of corticotropin, or corticotropin-independent due to primary adrenal neoplasms or nodular hyperplasia.1 Cushing's syndrome due to pituitary or ectopic corticotropin secretion can be clinically and biochemically indistinguishable.1,2 In recent years, advances in diagnostic imaging have led to the use of magnetic resonance imaging (MRI)3'4 and selective