Cushing's syndrome due to unilateral adrenal nodular hyperplasia with incomplete inhibition of the contralateral gland.

A 57-year-old woman was demonstrated to be affected by adrenocorticotropic hormone (ACTH)-independent Cushing's syndrome. Computed-axial tomography of the abdomen demonstrated an expansion of the left adrenal. In apparent contrast with these findings, adrenal scintigraphy demonstrated radiocholesterol uptake also by the right gland. At surgery, the left adrenal was found to be hard and enlarged and was excised, while the right gland was found of normal appearance and left in place. Histologic examination of the excised gland demonstrated nodular hyperplasia. Early after surgery, plasma cortisol returned to normal values with a normal circadian rhythm and complete inhibition by low dose dexamethasone; the response of plasma cortisol to ACTH was normal. The patient represents a rare case of unilateral adrenal nodular hyperplasia. Radiocholesterol uptake by the contralateral gland and early recovery from adrenal atrophy after surgery are exceptional findings and suggest incomplete inhibition of endogenous ACTH.