ACTH-independent Cushing's syndrome is due to the development of ectopic GIPR expression in the adrenal cortex, which arises secondary to germline or somatic loss of KDM1A expression [531] and gives rise to the secretion of cortisol upon release of GIP from the gut [532,533]. The gene discussed is GIP; the disease is Cushing syndrome due to macronodular adrenal hyperplasia.