Adrenocorticotropin-independent bilateral macronodular adrenocortical hyperplasia presenting as pre-Cushing's syndrome.

We report a man with pre-Cushing's syndrome due to ACTH-independent bilateral macronodular adrenocortical hyperplasia. Plasma ACTH was low and urinary 17-OHCS was not suppressed by a high dose of dexamethasone (8 mg), but plasma cortisol was responsive to exogenous ACTH. The adrenal glands were enlarged and contained multiple nodules composed of large clear cells and small compact cells. The steroid levels in the adrenal glands were lower than those in overt Cushing's syndrome due to the adrenocortical adenoma. This suggests that the tumor produces insufficient amounts of active hormones to have a clinical effect.