Most cases (approximately 80%) are caused by adrenocorticotropin (ACTH) hypersecretion—either by pituitary (Cushing’s disease [CD], 85–90%) or neuroendocrine non-pituitary tumors (ectopic ACTH syndrome [EAS], 10–15%) [2–4]. This evidence concerns the gene POMC and ACTH Syndrome, Ectopic.