These abnormalities are often linked to syndromes such as Multiple Endocrine Neoplasia (MEN-1, MEN-2A, MEN-4) or mutations in genes such as CASR, CDKN1A, CDKN1B, CDKN2C, and RET [13,14,15]. This evidence concerns the gene CDKN1A and multiple endocrine neoplasia type 1.