A Natural History of Adrenocorticotropin-Independent Bilateral Adrenal Macronodular Hyperplasia (AIMAH) from Preclinical to Clinically Overt Cushing's Syndrome

A 49-year-old man was referred to our hospital for the treatment of gallstones in 1993. Bilateral adrenal nodular masses were detected incidentally by abdominal computed tomography. He had no clinical signs of Cushing's syndrome such as central obesity, striae of skin and diabetes mellitus. We performed cholecystectomy and partial adrenalectomy of right adrenal gland as a biopsy, and diagnosed him as preclinical Cushing's syndrome due to adrenocorticotropin-independent bilateral adrenal macronodular hyperplasia (AIMAH) based on endocrinological and histological examinations. We followed him up for 7 years. During the observation period, the sizes of both adrenal glands increased gradually, and finally serum cortisol level increased beyond normal range, and he showed a Cushingoid appearance such as moon face and central obesity. His skin became atrophic and very fragile, and the bone mineral density of his lumbar spine was extremely low. Serum cortisol level was elevated, and plasma ACTHlevel was always suppressed. Urinary excretion of 17-hydroxycorticosteroid and free cortisol were increased. Diurnal rhythm of cortisol and ACTH was completely lost and high dose (8mg/day) dexamethasone did not suppress urinary 17-hydroxycorticosteroid excretion. He became clinically overt Cushing's syndrome. We recommended total adrenalectomy, but he refused it. It is important to know the natural history of preclinical Cushing's syndrome due to AIMAH when choosing an adequate treatment.