Multiple endocrine neoplasia (MEN) syndromes received their name because they predispose people to develop tumors of the endocrine glands. The endocrine system is comprised of glands that secrete hormones into the bloodstream that control numerous processes within the body. The endocrine system is instrumental in regulating mood, growth and development and metabolism, as well as sexual function and reproductive processes.
The major glands of the endocrine system affected by the MEN syndromes are the pituitary, thyroid, parathyroids, adrenals and pancreas. Currently, there are two distinct MEN syndromes: MEN1 and MEN2. In some ways, the two syndromes are similar, but there are important differences.