Preclinical Cushing's syndrome due to adrenocorticotropin-independent bilateral adrenocortical macronodular hyperplasia with concurrent excess of gluco- and mineralocorticoids.

A 48-year-old with bilateral adrenal incidentalomas was studied. Although the serum cortisol level was normal, autonomous cortisol secretion was shown by the loss of diurnal rhythm, no suppressibility by dexamethasone, and complete suppression of plasma adrenocorticotropin levels. Imaging analyses revealed bilateral adrenal masses, showing isotope uptake. He was diagnosed as preclinical Cushing's syndrome due to adrenocorticotropin-independent bilateral adrenocortical macronodular hyperplasia, confirmed histologically. Despite the undetectable plasma adrenocorticotropin level and renin activity, serum mineralocorticoids levels were not suppressed, which were decreased after subtotal adrenalectomy. It was suggested that hyperplastic adrenal glands could produce both gluco- and mineralocorticoids concomitantly.