Multiple endocrine neoplasia (MEN) is a group of disorders that affect the endocrine system, which is made up of glands that produce, store, and release hormones into the bloodstream. The disease typically involves tumors (overgrowth of tissue) in multiple endocrine glands that may be cancerous or noncancerous (benign) and may cause the glands to become overactive and overproduce hormones. There are many forms of MEN, with the most common being type 1 and type 2.
Multiple endocrine neoplasia runs in families meaning that the disease is passed down to family members through defects or mutations in certain genes, most commonly in MEN1 and RET (ret proto-oncogene). Only one parent needs to have the genetic defect to pass it on to a child.