Bilateral adrenocortical adenomas causing ACTH-independent Cushing's syndrome at different periods: a case report and discussion of corticosteroid replacement therapy following bilateral adrenalectomy.

We report a rare case of bilateral adrenocortical adenomas causing ACTH-independent Cushing's syndrome at different periods 9 yr apart. The subject, a 24-yr-old woman, in June 1989 had a typical Cushingoid appearance. Her baseline plasma cortisol levels did not show a diurnal rhythm and she had a very low baseline plasma ACTH level. Plasma cortisol levels could not be suppressed by overnight low-dose or two-day high-dose dexamethasone suppression test. Marked uptake of 131I-6beta-iodomethyl-19-norcholesterol (NP-59) was observed in the right adrenal gland. Abdominal computed tomography (CT) showed a right adrenal tumor. The right adrenal gland with adenoma was removed. The non-tumorous part of the adrenal cortex was atrophic. By April 1998, she had experienced a weight gain of more than 20 kg over a two-yr period. The baseline plasma cortisol levels were at the lower limit of the normal range with loss of diurnal rhythmicity. The baseline plasma ACTH levels were very low. Neither a two-day low-dose nor a two-day high-dose dexamethasone suppression test could suppress serum cortisol or urinary free cortisol levels. NP-59 adrenal scan revealed increased uptake of the left adrenal gland at 72 h after intravenous injection of the tracer. Abdominal CT and magnetic resonance imaging (MRI) all demonstrated a left adrenal mass. Left adrenalectomy was performed in June 1998; histological features showed a cortical adenoma and atrophic change in the non-tumorous part of the adrenal cortex. Elevated plasma ACTH levels after bilateral adrenalectomy could be suppressed with conventional corticosteroid replacement therapy and overnight low-dose dexamethasone suppression test.