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
ACTH level 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 (8 mg/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.