Multiple Endocrine Neoplasia (MEN): Types, Symptoms, Testing and Care
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer: What is multiple endocrine neoplasia?
Multiple endocrine neoplasia is a rare inherited or randomly occurring genetic condition that can cause tumors in multiple endocrine glands. MEN1 mainly involves parathyroid, gastroenteropancreatic and pituitary tumors, while MEN2 includes medullary thyroid cancer. These tumors may produce excess hormones, causing symptoms affecting digestion, blood pressure, blood sugar, mood and energy. [1]
What the research says
Hereditary medullary thyroid cancer is part of MEN2, and genetic testing has shifted care toward early detection. About 25% of adult medullary thyroid carcinoma cases are hereditary, caused by germline RET variants that lead to MEN2A and MEN2B. This clinical review reports that genetic testing and a better understanding of the natural course have moved presentation from advanced disease to early detection in people without symptoms, and that risk-reducing early thyroidectomy remains the cornerstone of preventing metastatic disease, with timing tailored to the specific variant (Shariq et al., J Clin Endocrinol Metab, 2025). [2]
Outcomes can vary by RET variant. A French study of 322 carriers of a RET codon 804 variant (65 index cases and 257 relatives) found 10-year disease-free survival of 61% in index cases and 90% among the 113 relatives who had surgery, of whom 62% had medullary thyroid cancer and 34% had isolated C-cell hyperplasia. The authors noted that long-term surveillance is needed because recurrence is possible several years after surgery. This is one variant group and does not describe every person with MEN2 (Suteau et al., Ann Endocrinol, 2025). [3]
What does the endocrine system do?
The endocrine system includes glands and organs that create and release hormones. Hormones carry messages through the blood to organs, skin, muscles and other tissues, helping coordinate what the body does and when it does it. [1]
The system includes the hypothalamus, pituitary gland, thyroid, parathyroid glands, adrenal glands, pineal gland, pancreas, ovaries and testes. The glands involved in MEN differ by type, and a person's symptoms depend on which tissues are affected and whether hormone levels change. [1]
What are the two main types of multiple endocrine neoplasia (MEN)?
Multiple endocrine neoplasia has two main types, MEN1 and MEN2, which have different tumor patterns and testing pathways. MEN1 is a genetic condition in which multiple tumors affect different parts of the endocrine system. MEN2 is a genetic polyglandular cancer syndrome associated with medullary thyroid cancer and an increased risk of other endocrine tumors. [1]
Feature | MEN1 | MEN2 |
Main pattern | Multiple tumors affecting endocrine tissues. | Medullary thyroid cancer plus risk of other endocrine tumors. |
Most commonly involved tissues | Parathyroid glands, gastroenteropancreatic tract and pituitary gland. | Thyroid C cells, adrenal glands and parathyroid glands. |
Associated gene | MEN1 gene. | RET gene. |
Can tumors be benign? | Most associated tumors are benign, but some can be cancerous and spread. | Pheochromocytomas are usually benign; medullary thyroid cancer can spread. |
Key testing concepts | Hormone blood tests, CT/MRI and MEN1 genetic testing. | Hormone blood tests, CT/MRI and RET genetic testing. |
The two types have different tumor patterns and testing pathways, so a healthcare provider must determine which type is present. Symptoms alone cannot identify MEN1 or MEN2.
Which glands and tumors are most often involved in MEN1?
People with MEN1 develop tumors in multiple endocrine glands. The most common affected areas are the parathyroid glands, the gastroenteropancreatic tract (including the pancreas, stomach and duodenum) and the pituitary gland. [1]
Most MEN1 tumors are benign, but some can be malignant and spread to other parts of the body. Affected glands may release excessive amounts of hormones, leading to symptoms and health problems. [1]
Less common tumors and growths can involve the thymus, bronchi, adrenal glands, fatty tissue, smooth muscle, collagen-producing tissue, facial skin, breast tissue and the nervous system. This list is not a prediction of what any individual will develop. [1]
What are the symptoms of MEN1 multiple endocrine neoplasia?
MEN1 symptoms vary widely because different glands and tumors can be involved. Symptoms may range from none or mild to severe and life-threatening, and people in the same family may have different symptoms or develop them at different ages.
Parathyroid-related symptoms
The parathyroid glands are the most commonly affected endocrine glands in MEN1. More than 90% of people with MEN1 develop hyperparathyroidism by age 50. [1]
Mild hyperparathyroidism may cause joint pain, muscle weakness, fatigue, depression, trouble concentrating and loss of appetite. More severe hyperparathyroidism may cause nausea and vomiting, confusion and forgetfulness, increased thirst and frequent urination, constipation and bone pain. [1]
Gastroenteropancreatic symptoms
Gastrinomas are tumors that release gastrin. Approximately 40% of adults with MEN1 develop multiple gastrinomas, usually in the first part of the duodenum and sometimes in the pancreas. Excess gastrin can cause the stomach to release too much acid, leading to abdominal pain, diarrhea, acid reflux and peptic ulcers. [1]
Insulinomas are benign insulin-secreting tumors that occur in approximately 10% of cases. They can cause low blood sugar, with symptoms such as confusion, shakiness, sweating, hunger, anxiety, heart palpitations and temporary vision changes. [1]
Pituitary-related symptoms
Approximately 25% of people with MEN1 develop benign pituitary tumors. Prolactinomas, which are benign tumors that release prolactin, are the most common pituitary tumors associated with MEN1. [1]
In women, prolactinoma-related symptoms may include menstrual changes unrelated to menopause, infertility, milky nipple discharge when not pregnant or breastfeeding and reduced interest in sex. In men, symptoms may include reduced interest in sex associated with low testosterone, erectile dysfunction and infertility. [1]
A large prolactinoma may also cause headaches, nausea or vomiting, double vision or decreased peripheral vision. These symptoms require medical evaluation because they can have several possible causes. [1]
MEN1-associated area | Examples of symptoms |
Parathyroid glands | Fatigue, joint pain, muscle weakness, concentration problems, nausea, thirst, frequent urination, constipation or bone pain. |
Gastrinomas | Abdominal pain, diarrhea, acid reflux and peptic ulcers. |
Insulinomas | Confusion, shakiness, sweating, hunger, anxiety, palpitations and temporary vision changes. |
Pituitary prolactinomas | Menstrual changes, infertility, nipple discharge, reduced sexual interest or erectile dysfunction. |
Large pituitary tumor | Headaches, nausea/vomiting or vision changes. |
This table is a summary, not a checklist for self-diagnosis. It is not a complete list because MEN1 can involve different tumors with different effects.
How does MEN2 multiple endocrine neoplasia involve medullary thyroid cancer and other tumors?
All people with MEN2 develop medullary thyroid cancer, also called MTC. MTC begins in C cells of the thyroid gland. These cells make calcitonin rather than thyroid hormone. [1]
MTC can spread to lymph nodes and other organs. Symptoms may include a lump or pain in the front of the neck, hoarseness, coughing, trouble swallowing or shortness of breath. The primary treatment is surgery to remove the thyroid. [1]
People with MEN2 also develop one or both of the following: pheochromocytoma and hyperparathyroidism.
Pheochromocytoma
Pheochromocytoma is a tumor in the middle of one or both adrenal glands. It is made of chromaffin cells, which release certain hormones. Approximately 50% of people with MEN2 develop a pheochromocytoma. Most are benign, while approximately 10% to 15% may be malignant and spread. [1]
Symptoms occur when the tumor releases too much adrenaline or noradrenaline. They often happen in spells and may include high blood pressure, headache, unexplained excessive sweating, a pounding or fast or irregular heartbeat and shakiness. Some pheochromocytomas do not make these hormones and do not cause symptoms. [1]
Hyperparathyroidism
Hyperparathyroidism occurs when the parathyroid glands release too much parathyroid hormone, causing blood calcium levels to rise. In MEN2, it is usually caused by a benign parathyroid tumor or enlargement of two or more parathyroid glands. Symptoms may include joint pain, muscle weakness, fatigue, depression, trouble concentrating, loss of appetite, nausea and vomiting, increased thirst and frequent urination, constipation and bone pain. [1]
Who does MEN affect?
MEN affects males and females equally. MEN1 has been diagnosed in children as young as 8 and adults as old as 80, so age at diagnosis can vary widely. [1]
MEN is rare: approximately 1 in 30,000 people for MEN1 and approximately 1 in 35,000 for MEN2. Some researchers think many cases are undiagnosed or misdiagnosed, so the actual rate could be higher. [1]
What causes multiple endocrine neoplasia?
Both MEN1 and MEN2 are caused by gene mutations. A mutation may be inherited from a biological parent or occur randomly during embryo development. If a biological parent has MEN, their child has a 50% chance of having the condition. [1]
MEN1 is caused by mutations in the MEN1 gene, a tumor-suppressor gene that helps control cell division and instruct cells when to die. When this gene malfunctions, certain cells may continue growing and reproducing, allowing tumors to form. [1]
MEN2 is caused by mutations in the RET gene, which plays a role in cell division and regulation of cell death. Mutations can lead to uncontrolled cell growth in certain organs and glands. [1]
A gene mutation is not something a person causes through lifestyle. A family history can be an important reason to discuss genetic counseling or testing with a qualified provider.
How is MEN diagnosed?
Diagnosis depends on the type of MEN and the combination of tumors, hormone findings, imaging and genetic information. Symptoms alone cannot establish the diagnosis.
MEN1 diagnosis and tests
A person may be diagnosed with MEN1 when they have at least two of the three endocrine tumors associated with the condition: a parathyroid tumor, a pituitary tumor and/or a tumor in the gastroenteropancreatic tract. Diagnosis is also possible when a person has one associated tumor and a family history of MEN1. [1]
Before diagnosing MEN1, providers first identify one or more tumors. Blood tests may detect elevated hormone levels. For example, high parathyroid hormone together with high blood calcium may indicate a parathyroid tumor. CT or MRI scans can help find and diagnose tumors, and genetic testing of the MEN1 gene can confirm a MEN1 diagnosis. [1]
MEN2 diagnosis and tests
A person may be diagnosed with MEN2 when they have medullary thyroid cancer plus pheochromocytoma and/or parathyroid enlargement or a parathyroid tumor. [1]
Blood tests may show higher-than-normal calcitonin, which can indicate MTC; high parathyroid hormone, which may indicate a parathyroid tumor or enlargement; or high catecholamines, which may indicate pheochromocytoma. CT or MRI scans can help locate tumors, and genetic testing of the RET gene can confirm a MEN2 diagnosis. [1]
Diagnostic element | How it may be used |
Symptom and family-history review | Identifies patterns, affected relatives and possible hormone-related symptoms. |
Hormone blood tests | Looks for hormone levels associated with particular tumors. |
CT or MRI scans | Helps find and diagnose tumors. |
MEN1 genetic testing | Can confirm a MEN1 diagnosis when the clinical picture supports it. |
RET genetic testing | Can confirm a MEN2 diagnosis when the clinical picture supports it. |
How is MEN treated?
Treatment depends entirely on which endocrine glands and organs are affected. Care usually requires a team that may include endocrinologists, surgeons, oncologists and pediatricians when appropriate. [1]
Treatment may include medications to treat symptoms or counteract the effects of excess hormones, surgery to remove tumors or an affected gland, hormone replacement after a gland is removed, and cancer treatment such as chemotherapy or radiation therapy when cancer has spread. [1]
For MEN2, thyroid-removal surgery is the primary treatment for medullary thyroid cancer. Each person's treatment plan is specific to the tumors, hormone effects and cancer status involved. [1]
Treatment approach | When it may be considered |
Medication | To treat symptoms or counteract excess hormones. |
Tumor or gland surgery | To remove tumors or an affected endocrine gland. |
Hormone replacement | When an endocrine gland is surgically removed. |
Cancer treatment | When a cancerous tumor has spread. |
Multidisciplinary care | Because endocrine, surgical and cancer-related decisions may overlap. |
There is currently no cure for MEN, but it is manageable. Healthcare providers treat changes in each gland as they happen with surgery or medication. [1]
What is the outlook?
The prognosis for MEN depends on how early it is diagnosed, which endocrine glands are affected, whether tumors are benign or cancerous, which treatment is used and whether a cancerous tumor has spread. [1]
Because MEN can look different from one person to another, the healthcare provider is best positioned to explain the expected course and monitoring plan.
Can MEN be prevented?
MEN cannot be prevented because it results from genetic mutations that are inherited or occur randomly during embryo development. Prevention in the usual lifestyle sense is therefore not possible. [1]
If a first-degree relative, such as a biological parent or sibling, has been diagnosed with MEN, talk with a healthcare provider about genetic testing. If a person has MEN, genetic testing may help detect tumors in earlier phases. [1]
Genetic testing is a personal healthcare decision. A qualified provider or genetics professional can discuss what a result might mean for the person and family before testing is performed.
How can people live with multiple endocrine neoplasia (MEN)?
People diagnosed with MEN need regular healthcare visits to monitor the condition and see whether treatment is working. Monitoring may involve more than one specialty because multiple endocrine glands and tumor types can be involved. [1]
A family member's diagnosis can also be a reason for biological parents or siblings to discuss genetic testing with a provider. New concerning symptoms or changes in the body should prompt a healthcare conversation rather than self-diagnosis.
Question to bring to the care team | Why it matters |
What type of MEN do I have? | MEN1 and MEN2 involve different tumor patterns and testing pathways. |
Which glands or tumors are affected? | Helps connect symptoms and monitoring to the person's situation. |
What symptoms should I watch for? | Clarifies when a new change should be reported. |
What are my treatment options? | Supports shared discussion of medication, surgery or other care. |
What are the benefits and risks of each treatment? | Helps the person understand major decisions. |
How long might treatment take to work? | Sets expectations for follow-up. |
Should biological relatives be tested? | Opens a conversation about family screening. |
When should you contact a healthcare provider?
Contact a healthcare provider if you have new concerning symptoms or changes to your body. If you have been diagnosed with MEN, regular visits are needed to monitor the condition and assess whether treatment is working.
If a biological parent or sibling has MEN, discuss genetic testing with a healthcare provider. MEN can be inherited even though some cases occur randomly.
Conclusion: MEN is manageable with informed, ongoing care
Multiple endocrine neoplasia is a rare genetic condition that can affect several endocrine glands and tissues. MEN1 most often involves the parathyroid glands, gastroenteropancreatic tract and pituitary gland, while MEN2 is associated with medullary thyroid cancer and may also involve the adrenal and parathyroid glands.
Symptoms vary widely, and diagnosis may require hormone testing, imaging, genetic testing and review of family history. There is no cure, but MEN is manageable through monitoring, medication, surgery and coordinated specialty care. For more clear, compassionate health explainers, explore Rinnit.com's health library and bring personal questions to a qualified endocrine or genetics care team.
Frequently Asked Questions
What are the two types of multiple endocrine neoplasia?
The two main types are MEN1 and MEN2. MEN1 involves multiple endocrine tumors, especially in the parathyroid glands, gastroenteropancreatic tract and pituitary gland. MEN2 includes medullary thyroid cancer and increased risk of other endocrine tumors.
Is multiple endocrine neoplasia inherited?
Multiple endocrine neoplasia can be inherited from a biological parent or occur randomly during embryo development. If a biological parent has MEN, a child has a 50% chance of having the condition.
What gene causes MEN1?
MEN1 results from mutations in the MEN1 gene, which is a tumor-suppressor gene involved in controlling cell division and cell death.
What gene causes MEN2?
MEN2 results from mutations in the RET gene, which plays a role in cell division and regulation of cell death.
What cancers are associated with MEN2?
All people with MEN2 develop medullary thyroid cancer. It can spread to lymph nodes and other organs.
What symptoms can MEN1 cause?
MEN1 symptoms depend on the affected gland or tumor. Possible symptoms include fatigue, muscle weakness, joint pain, digestive symptoms, low-blood-sugar symptoms, menstrual or sexual-function changes, headaches, nausea, vomiting and vision changes.
What symptoms can MEN2 cause?
MEN2 may cause a neck lump or pain, hoarseness, coughing, trouble swallowing or shortness of breath from medullary thyroid cancer. Pheochromocytoma may cause spells of high blood pressure, headache, excessive sweating, pounding or irregular heartbeat and shakiness. Hyperparathyroidism may cause fatigue, digestive symptoms, thirst, frequent urination or bone pain.
How is MEN diagnosed?
Diagnosis may include health and family-history review, hormone blood tests, CT or MRI scans and genetic testing. MEN1 and MEN2 have different clinical criteria and gene tests.
Can genetic testing detect MEN early?
If a person has MEN, genetic testing may help detect tumors in their early phases. Relatives with a first-degree family history should discuss testing with a healthcare provider.
Is there a cure for MEN?
There is currently no cure, but MEN is manageable. Providers treat changes in each gland with surgery or medication and monitor the condition over time.
What treatments are used for MEN?
Treatment may include medications, surgery to remove tumors or glands, hormone replacement after gland removal and cancer treatment if a cancerous tumor has spread. Care depends on the affected organs and tumors.
Who treats multiple endocrine neoplasia?
Care often involves a team that may include an endocrinologist, surgeon, oncologist and pediatrician when appropriate.
Can lifestyle changes prevent MEN?
No. MEN is caused by genetic mutations that are inherited or occur randomly during embryo development, so it cannot be prevented through lifestyle changes.
References
Cleveland Clinic. Multiple Endocrine Neoplasia (MEN): Types & Symptoms. Cleveland Clinic. Last updated May 23, 2022. https://my.clevelandclinic.org/health/diseases/23088-multiple-endocrine-neoplasia-men
Shariq OA, Waguespack SG, Hamidi S, et al. Approach to the Patient: Hereditary Medullary Thyroid Carcinoma. J Clin Endocrinol Metab. 2025;110(9):2685-2697. PMID 40105880. https://doi.org/10.1210/clinem/dgaf089
Suteau V, Lebeault M, Schlumberger M, et al. Natural history of medullary thyroid carcinoma in MEN 2 patients carrying a variant at codon 804 in the RET proto-oncogene: A study by the French Neuroendocrine Tumor Group (GTE). Ann Endocrinol (Paris). 2025;86(2):101705. PMID 39842635. https://doi.org/10.1016/j.ando.2025.101705
Disclaimer
This article is for general educational purposes and is not a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified healthcare professional with any questions about a medical condition or treatment.
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