These are often gene defects in the context of multiple endocrine neoplasia syndrome type 1 (MEN1 caused by MEN1 gene defects), MEN4 (caused by CDKN1B gene defects), AIP gene defects leading to familial isolated pituitary adenoma (FIPA) syndrome, Carney complex (caused by PRKAR1A gene defects) and other rare causes [5]. Here, CDKN1B is linked to familial isolated pituitary adenoma.