Definition:

Multiple endocrine neoplasias (MEN) are autosomal dominant syndrome which is characterized by the occurrence of tumors involving two or more endocrine glands. Four major forms of MEN are recognized, namely MEN1, MEN2A, MEN2B and MEN4. MEN1, which is also referred as Wermer's syndrome, is characterized by parathyroid adenoma, gastrinoma, and pituitary adenoma. Gastrinomas are the most common type, leading to the Zollinger-Ellison Syndrome (see H01522). MEN2 are characterized by medullary thyroid cancer (MTC) and includes three subtypes: MEN2A (Sipple's syndrome), MEN2B (MEN3) and familial MTC. MEN2A develop MTC in association with phaeochromocytoma and parathyroid tumors. MEN2B develop MTC in association with marfanoid habitus, mucosal neuromas, medullated corneal fibers and intestinal autonomic ganglion dysfunction, leading to megacolon. MEN4, also referred to as MENX, appears to have signs and symptoms similar to those of type 1. However MEN4 patients have mutations in other genes. The mutations in their responsible genes are found in Each MEN syndrome.