The short answer
This guide helps readers understand inherited endocrine tumor syndromes, hormone testing, imaging, surveillance, and family implications. It supports—but does not replace—individual medical, legal, or coverage advice.
The goal is to understand inherited endocrine tumor syndromes, hormone testing, imaging, surveillance, and family implications.
Ask which MEN type and gene finding apply.
Keep a list of glands, tumors, surgeries, hormones, and medicines.
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This page is for people and families affected by multiple endocrine neoplasia (MEN). It covers the types, genetic testing, risk-reducing surgery, and lifelong checks.
What multiple endocrine neoplasia is
Multiple endocrine neoplasia (MEN) is a group of inherited conditions. Each one causes tumors in the endocrine glands. Those are the glands that make hormones.
Some of these tumors are benign, which means not cancer. Some are cancer. Many cause harm in a third way. They make far too much of one hormone, and that hormone changes how the body works.
There are three named types: MEN1, MEN2 and MEN4. MEN2 splits again into MEN2A and MEN2B. Each type comes from a change in a different gene. Each puts a different set of glands at risk.
MEN1 affects about 1 in 30,000 people. MEN2 affects about 1 in 35,000. MEN4 is rare, and its true frequency is not known.
Your type is the first thing to pin down. It sets your whole monitoring plan.
MEN1: parathyroid, pituitary and pancreas
MEN1 comes from a change in the MEN1 gene. That gene makes a protein called menin. Menin normally holds tumor growth in check.
MEN1 targets three main sites.
- The parathyroid glands. These are four small glands in the neck. They control the calcium level in your blood. Overactive parathyroid glands (hyperparathyroidism) are the most common feature of MEN1.
- The pituitary gland. This sits at the base of the brain and directs other glands. Pituitary adenomas (usually benign tumors) can form here.
- The pancreas. Neuroendocrine tumors can form in the islet cells. Some make hormones and some do not.
In one group of young people with MEN1 found before age 21, NCI reports overactive parathyroid glands in 75%, pituitary tumors in 34% and pancreas tumors in 23%.
MEN2A and MEN2B: the RET gene
MEN2 comes from a change in the RET gene. The change switches the gene on too strongly.
The central risk in MEN2 is medullary thyroid carcinoma, or MTC. This is a cancer of the C cells of the thyroid. C cells make a hormone called calcitonin. MTC is not the common kind of thyroid cancer, and it behaves differently.
MEN2A is the more common form. About 95% of people with MEN2A develop MTC. About 50% develop a pheochromocytoma. That is an adrenal gland tumor that pours out adrenaline-type hormones. Parathyroid disease affects 20% to 30%.
MEN2B is rarer and more aggressive. Nearly everyone with MEN2B develops MTC, and it starts younger. About 50% develop a pheochromocytoma. MEN2B makes up about 5% of all MEN2.
Familial medullary thyroid carcinoma (FMTC) sits inside the MEN2A group. In FMTC, MTC is the only feature.
MEN4
MEN4 comes from a change in the CDKN1B gene. Overactive parathyroid glands are the most common feature, then pituitary tumors. MEN4 is rare.
Why the exact gene result matters so much
In MEN2, the precise spot inside the RET gene drives the plan. Doctors sort RET changes into risk levels. More than 95% of people with MEN2B have a change at codon 918, which is in the highest-risk group.
Ask for your genetic report in writing. You want three things on it: the gene name, the exact variant, and the risk level. Do not rely on a relative's report alone.
Risk-reducing thyroid surgery in MEN2
MTC risk in MEN2 is very high. So the thyroid is often removed before any cancer appears. This is called prophylactic, or risk-reducing, thyroidectomy. Timing follows the RET change.
Children with MEN2A and certain RET changes usually have the thyroid removed before age 5. Infants with MEN2B and certain RET changes usually have the thyroid removed.
After the thyroid is out, thyroid hormone replacement is needed for life. It is not a temporary bridge.
What surveillance looks like
In MEN2. NCI's family page says pheochromocytoma checks begin at age 10 and continue for life. NCI's professional summary mentions guidelines that start at age 11. Ask your team which schedule they follow.
In MEN1. NCI says checks begin by age 5 and continue for life. Tests depend on age. They may include yearly blood tests for calcium, parathyroid hormone, gastrin, glucagon, proinsulin, chromogranin A, prolactin and IGF-1. NCI's professional summary lists a brain MRI and a belly CT scan every 1 to 3 years.
That is a lot of tubes. Ask for one standing annual order, so you are not chasing separate lab slips each year.
Testing family members
MEN is inherited in an autosomal dominant pattern. This means one changed copy of the gene, from either parent, is enough to cause the condition. Each child of a person with MEN2 has a 50% chance of inheriting the RET change.
Testing relatives early matters, because thyroid surgery timing depends on the RET result. Ask the genetics team when at-risk children should be tested.
NCI says about half of MEN2B cases come from a new gene change rather than an inherited one. So a clean family history does not rule MEN2B out.
When to call the team
Signs of high blood calcium. Overactive parathyroid glands push blood calcium up. Contact your provider if you notice:
- Nausea or vomiting, or poor appetite
- Constipation
- More thirst or more urination
- Muscle weakness or twitches
- Tiredness or confusion
- Bone pain
Most people with high calcium have no symptoms at all, and it is usually found on a routine blood test. Symptoms alone cannot tell you your calcium is safe.
Signs of a pheochromocytoma. These are:
- High blood pressure
- Headache
- Heavy sweating for no clear reason
- A strong, fast or irregular heartbeat
- Shakiness
- Looking very pale
The most common sign is high blood pressure that is hard to control. NCI warns that very high blood pressure can cause an irregular heartbeat, a heart attack, a stroke, or death. If these signs come on suddenly and severely, call 911. Do not wait it out.
What this page cannot do
This page describes patterns across MEN as a group. It cannot set your personal screening dates or surgical timing. Those come from your gene result, your own test history, and an endocrine team that treats MEN regularly.
Sources
- Multiple Endocrine Neoplasia — MedlinePlus Genetics
- Multiple Endocrine Neoplasia (MEN) Syndromes — National Cancer Institute
- Childhood MEN1 Syndrome — National Cancer Institute
- Childhood MEN2 Syndrome — National Cancer Institute
- Childhood Multiple Endocrine Neoplasia Syndromes Treatment (PDQ), Health Professional Version — National Cancer Institute
- Hypercalcemia — MedlinePlus Medical Encyclopedia
- Pheochromocytoma and Paraganglioma Treatment (PDQ), Patient Version — National Cancer Institute
Common questions
What is multiple endocrine neoplasia?
MEN is a group of inherited conditions that cause tumors in the endocrine glands, the glands that make hormones. Some of these tumors are benign and some are cancer. Many cause harm in a third way: they make far too much of one hormone, and that hormone changes how the body works. There are three named types, MEN1, MEN2 and MEN4, and MEN2 splits again into MEN2A and MEN2B.
Why does the exact gene result matter so much?
In MEN2, the precise spot inside the RET gene drives the whole plan. Clinicians sort RET changes into three risk levels: highest risk is the p.Met918Thr change, high risk covers changes at codon 634 plus p.Ala883Phe, and moderate risk covers all other activating changes. Ask for your genetic report in writing showing the gene name, the exact variant and the risk level, and do not rely on a relative's report alone.
Why would a thyroid be removed before there is any cancer?
In MEN2 the risk of medullary thyroid carcinoma is close to certain, so the thyroid is often removed before cancer appears. Timing follows the risk level. NCI says children with MEN2B have surgery in infancy, and children with MEN2A usually have it before age 5. Some moderate-risk changes may allow surgery at age 5 or later. After the thyroid is out, thyroid hormone replacement is needed for life. It is not a temporary bridge.
When should relatives be tested?
MEN is inherited in an autosomal dominant pattern, so each child of a person with MEN2 has a 50% chance of inheriting the RET change. NCI says young relatives of people with MEN2A are tested before age 5. For MEN2B, ask the genetics team how soon after birth to test. About half of MEN2B cases come from a new gene change, so a clean family history does not rule it out.
Which symptoms should make me call the team?
Signs of high blood calcium include nausea or vomiting, poor appetite, constipation, more thirst or urination, muscle weakness or twitches, tiredness or confusion, and bone pain. Most people with high calcium have no symptoms at all, so symptoms alone cannot tell you your calcium is safe. Signs of a pheochromocytoma include high blood pressure that is hard to control, headache, heavy sweating for no clear reason, a strong, fast or irregular heartbeat, shakiness and looking very pale. If those come on suddenly and severely, call 911.
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Sources last checked: 2026-08-13 what this meansLast updated: 2026-09-29Next planned review: 2027-07-22
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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