multiple endocrine neoplasia type 1

Multiple endocrine neoplasia type 1 (MEN1) is a hereditary tumor-predisposition syndrome that primarily affects hormone-producing glands such as the parathyroids, pituitary, and pancreas. It is caused by pathogenic variants in the MEN1 gene, which normally helps regulate cell growth. The condition can appear at any age but often emerges in adolescence or early adulthood when hormone-related symptoms draw medical attention. MEN1 is considered uncommon, affecting roughly 1 to 9 people per 100,000. Because individuals may develop different combinations of tumors, the condition requires lifelong medical follow-up.

MEN1 chiefly involves endocrine glands. Over time, many individuals develop parathyroid overactivity, which can lead to high calcium levels, kidney stones, or bone thinning. Pituitary adenomas are also common and may produce excess hormones such as prolactin, resulting in menstrual changes, infertility, or unexpected breast milk production. A subset of people develop foregut neuroendocrine tumors, especially in the pancreas, which can secrete insulin or other hormones and cause low blood sugar or digestive symptoms. Less frequently, carcinoid tumors or adrenal cortex growths occur. Not all individuals experience all features, and severity varies considerably, even among relatives who share the same genetic change.

MEN1 is caused by pathogenic variants in the MEN1 gene. The MEN1 gene supplies instructions for a protein called menin that helps control how cells grow and divide, particularly in endocrine tissues. The condition follows an autosomal dominant inheritance pattern, meaning one altered copy of the gene is enough to increase tumor risk, and each child of an affected individual has a 50 percent chance of inheriting the variant. Not everyone who carries a pathogenic MEN1 variant will develop tumors (reduced penetrance), and the types of tumors can differ greatly between affected family members (variable expressivity). Because of these complexities, genetic counseling is strongly recommended for individuals and families navigating testing and family-planning decisions.

Treatment planning for MEN1 depends on the location, size, and behavior of each tumor as well as the individual’s overall health. Management often involves a multidisciplinary team that may include endocrinologists, surgeons, medical oncologists, and genetic counselors. Care strategies can include surgery to remove tumors, local or regional therapies such as radiation, systemic treatment approaches for hormonally active or metastatic tumors, and supportive care to control symptoms of hormone excess. Regular surveillance is an essential part of long-term care, helping to identify potential complications before they become serious. Patients should discuss management options with their healthcare team to determine which strategies are most appropriate for their specific situation.

Long-term outlook in MEN1 varies widely and depends on which tumors develop, how early they are detected, and how effectively hormone levels are controlled. Many individuals lead productive lives when tumors are identified early and treated promptly, but recurring or multiple tumors can require ongoing interventions and careful monitoring. Outcomes described in medical literature continue to evolve as standards of care improve. Families often find it helpful to connect with multidisciplinary teams experienced in MEN1 and to engage in regular surveillance to support the best possible quality of life. Genetic counseling can help relatives understand their own risks and plan appropriate monitoring.

MEN1 remains an active research area with numerous ongoing clinical trials exploring new diagnostic tools, medical therapies, and surveillance strategies. Individuals interested in participating can search ClinicalTrials.gov or consult their care team about eligibility.