A rare case of adrenocorticotropic hormone (ACTH)-independent macroadrenal hyperplasia showing ectopic production of ACTH.

A 57-year-old Japanese man presented with drug-resistant hypertension without Cushingoid features. Endocrinological tests revealed autonomous secretion of cortisol with suppressed plasma adrenocorticotropic hormone (ACTH). Imaging examinations showed multiple macronodules in the bilateral adrenal gland. These findings were consistent with subclinical Cushing's syndrome caused by ACTH-independent macronodular adrenal hyperplasia (AIMAH). Left adrenalectomy was performed and the resected adrenal lesion was consistent with the pathological diagnosis of AIMAH. Furthermore, in resected tissue, we demonstrated intraadrenal production of ACTH by immunohistochemical analysis and RIA. This is a very rare case of AIMAH showing ectopic production of ACTH, which may be associated with autonomous cortisol secretion.