Multiple endocrine neoplasia, type 1 (MEN 1), sometimes called Wermer's syndrome, is a rare disorder that causes tumors in the endocrine glands and parts of the small intestine and stomach. In MEN 1, the endocrine glands — usually the parathyroids, pancreas and pituitary — grow tumors and release excessive amounts of hormones that can lead to disease. However, the tumors are usually noncancerous (benign).

The excess hormones can cause a wide variety of signs and symptoms. These can include tiredness, bone pain, broken bones, kidney stones, and ulcers in the stomach or intestines. MEN 1 can't be cured. But regular testing can detect problems, and doctors can provide treatment as needed.

MEN 1 is an inherited disorder. That means people who have a genetic change that causes MEN 1 can pass it on to their children.


Signs and symptoms of MEN 1 include the following:

  • Tiredness.
  • Bone pain.
  • Broken bones.
  • Kidney stones.
  • Ulcers in the stomach or intestines.

Symptoms are caused by the release of too many hormones in the body.


MEN 1 is caused by a change in the MEN1 gene. That gene controls how the body makes a protein called menin. Menin helps to keep cells in the body from growing and dividing too quickly.

Research has found that there are many different changes in the MEN1 gene that can cause the MEN 1 condition to develop. People who have one of those genetic changes can pass it on to their children. Many people with a change in the MEN1 gene inherit it from a parent. But some people are the first in their family to have a new MEN1 gene change that doesn't come from a parent.

Risk factors

  • Children with a parent who has a genetic change in the MEN1 gene are at risk of inheriting that genetic change and developing MEN 1. A child who has a parent with a genetic change for MEN 1 has a 50% chance of inheriting the same genetic change.
  • Parents and siblings of people who have a change in the MEN1 gene also are at risk of having the same genetic change. That's true even if they have not yet developed symptoms of MEN 1.

Multiple endocrine neoplasia, type 1 (MEN 1) care at Mayo Clinic

Feb. 14, 2024
  1. Jameson JL, et al., eds. Multiple endocrine neoplasia type 1. In: Endocrinology: Adult and Pediatric. 7th ed. Saunders Elsevier; 2016. https://www.clinicalkey.com. Accessed Oct. 11, 2020.
  2. Melmed S, et al. Multiple endocrine neoplasia. In: Williams Textbook of Endocrinology. 14th ed. Elsevier; 2020. https://www.clinicalkey.com. Accessed Oct. 11, 2020.
  3. Multiple endocrine neoplasia type 1. National Institute of Diabetes and Digestive and Kidney Diseases. https://www.niddk.nih.gov/health-information/endocrine-diseases/multiple-endocrine-neoplasia-type-1. Accessed Oct. 11, 2020.
  4. Warner K. Allscripts EPSi. Mayo Clinic. Oct. 26, 2020.
  5. Multiple endocrine neoplasia, type 1 (MEN 1). Merck Manual Professional Version. https://www.merckmanuals.com/professional/endocrine-and-metabolic-disorders/multiple-endocrine-neoplasia-men-syndromes/multiple-endocrine-neoplasia,-type-1-men-1. Accessed Oct. 11, 2020.
  6. Arnold A. Multiple endocrine neoplasia type 1: Treatment. https://www.uptodate.com/contents/search. Accessed Oct. 11, 2020.
  7. Kearns AE (expert opinion). Mayo Clinic. Oct. 30, 2020.
  8. Kamilaris CDC, et al. Multiple endocrine neoplasia type 1 (MEN1): An update and the significance of early genetic and clinical diagnosis. Frontiers in Endocrinology. 2019; doi: 10.3389/fendo.2019.00339.


Products & Services