Cushing's syndrome due to unilateral adrenocortical hyperplasia.

A 49-year-old woman with Cushing's syndrome due to unilateral adrenal hyperplasia is presented. She had developed obesity and menopause for 2 years, but no hypertension or hypertrichosis was observed. Although plasma adrenocorticotropin and serum cortisol levels were within normal ranges, the circadian rhythm has completely disappeared. Free thyroxine and triiodothyronine levels were decreased. Adrenocorticotropin did not respond to corticotropin-releasing hormone, and urinary excretion of 17-hydroxycorticosteroids was not suppressed by dexamethasone. Abdominal computed tomography and 131I-Adosterol scintigraphy demonstrated a unilateral functioning mass in the left adrenal gland. The resected left adrenal mass was pathologically diagnosed as the rare condition of adrenocortical nodular hyperplasia.