Until recently, there were only few reports regarding the genetic changes in ACTHomas, except for familial Cushing’s disease, such as multiple endocrine neoplasm type 1 (MEN1), MEN4, and familial isolated pituitary adenomas (FIPAs), and the germline mutations associated with these hereditary syndromes were identified in the MEN1, CDKN1B, and AIP genes, respectively. This evidence concerns the gene CDKN1B and familial isolated pituitary adenoma.