About 80% of CS cases are due to ACTH secretion by a pituitary adenoma, about 20% are due to ACTH secretion by nonpituitary tumors (ectopic ACTH syndrome [EAS]), and 1% are caused by corticotropin-releasing hormone (CRH)-secreting tumors (Alexandraki and Grossman, 2010; Ejaz et al., 2011; Ballav et al., 2012). This evidence concerns the gene CRH and ACTH Syndrome, Ectopic.