The ACTH-dependent forms are characterized by excessive ACTH production from a corticotroph adenoma, which is also referred to as pituitary-dependent CS or Cushing's disease; an ectopic tumor, also referred to as ectopic ACTH syndrome; or rarely from excessive hypothalamic secretion of CRH that may also arise from an ectopic tumor. This evidence concerns the gene POMC and ACTH-producing pituitary gland adenoma.