Cushing's syndrome due to unilateral nodular adrenal hyperplasia: a new pathophysiological entity?

A case is presented of a 43-year-old Caucasian female with Cushing's syndrome, malignant hypertension and renal insufficiency. Plasma cortisol values were elevated (19.5 microgram/100 ml at 0800 h and 18.5 microgram/100 ml at 2200 h) with loss of diurnal variation and failure of suppression with low and high dose dexamethasone. 17-ketogenic steroid excretion remained unchanged after metyrapone administration. Adrenal vein plasma cortisol values showed prominent left-sided gradient. Gross, histologic and electron-microscopic examination of the left adrenal gland revealed changes of nodular adrenal hyperplasia. The presence of a suppressed right adrenal gland was confirmed post-operatively by a five day ACTH infusion. This case may represent a previously unreported variant of Cushing's syndrome due to unilateral nodular adrenal hyperplasia.