ACTH-independent macronodular adrenal hyperplasia.

Adrenocorticotropic hormone- (ACTH-)independent macronodular adrenal hyperplasia (AIMAH) is an infrequent cause of Cushing's syndrome (CS). AIMAH presents as incidental radiological finding or with subclinical or overt CS, occasionally with secretion of mineralocorticoids or sex steroids. The pathophysiology of this entity is heterogeneous. The aberrant adrenal expression and function of one or several G-protein-coupled receptors can lead to cell proliferation and abnormal regulation of steroidogenesis. In several familial cases of AIMAH, specific aberrant hormone receptors are functional in the adrenal of affected members. Additional somatic genetic events related to cell cycle regulation, adhesion and transcription factors occur in addition in the various nodules over time. Other mechanisms, such as Gsp or ACTH receptor mutations and paracrine adrenal hormonal secretion, have been rarely identified in other cases of AIMAH. The identification of aberrant receptors can offer a specific pharmacological approach to prevent progression and control abnormal steroidogenesis; alternatively, unilateral or bilateral adrenalectomy becomes the treatment of choice.