It may be caused by an excess of ACTH production (usually by pituitary adenomas, less frequently by extrapituitary ACTH- or CRH-secreting tumors) or it can result from the excess secretion of cortisol by unilateral adrenocortical tumors (benign or malignant) or by bilateral adrenal hyperplasia or dysplasia [126]. The gene discussed is POMC; the disease is dysplasia.