Acth-independent Cushing's syndrome: bilateral cortisol-producing adrenal adenomas.

ACTH-independent Cushing's syndrome (CS) usually results from a solitary adrenocortical adenoma. We recently encountered a patient with ACTH-independent CS associated with bilateral adrenal enlargement. The evaluation led us to consider some rare but interesting entities. The patient was a 69 year-old woman who had a 10-15 year history of controlled hypertension, back pain associated with osteoporosis, easy bruising, and truncal obesity. Her medications included conjugated estrogens. Physical examination revealed classical features of CS. She had a raised blue lesion on her buccal mucosa. Plasma cortisol concentrations were elevated at 36 (a.m.) and 38 (p.m.) microg/dL. Urinary free cortisol was normal at baseline (65 microg/24 hours) but failed to suppress adequately in response to the low-dose dexamethasone suppression test (75 microg/24 hours). The plasma ACTH concentration was undetectable. Plasma cortisol concentrations failed to suppress (37 microg/dL) with an 8 mg overnight dexamethasone test. A CT scan of the abdomen revealed bilateral adrenal masses. The possibilities of food-induced CS and primary pigmented nodular adrenal disease were excluded by a lack of marked stimulation in cortisol secretion to a mixed-meal and dermatologic confirmation of the buccal mucosa lesion as an angioma and not a blue nevus. Adrenal venous sampling showed cortisol secretion from both adrenals. The patient underwent bilateral adrenalectomy with pathology confirming bilateral adenomas. This case illustrates an unusual application of selective venous sampling in the CS evaluation and raises questions about the pathogenesis of cortisol-secreting adrenocortical adenomas.