This page was reviewed under our medical and editorial policy by
Maurie Markman, MD, President, Medicine & Science
This page was updated on February 28, 2022.
Multiple endocrine neoplasia (MEN) syndromes are rare genetic disorders of the endocrine system, which is the body’s grouping of hormone-producing glands. The glands in the network produce hormones—also known as the chemical substances that travel through the bloodstream to help cells and tissues do their job, including growth, digestion and sexual function.
This condition is also known as:
People with MEN syndromes are likely to develop tumors—either benign (noncancerous) or malignant (cancerous)—on the endocrine glands, as well as other organs and tissues.
There are different forms of multiple endocrine neoplasia. The genes that are affected, the types of hormones involved, and the signs and symptoms of the disease determine the type.
Among the most common are type 1 (MEN1) and type 2 (MEN2).
Type 2 has subtypes:
About one in 30,000 people are affected by multiple endocrine neoplasia type 1, according to the U.S. National Library of Medicine. Type 2 is even less common, with about one case in 35,000 people.
A mutation in the MEN1 gene—which provides the blueprint for making the protein menin, a tumor suppressor—is the cause of type 1.
Typically, every cell has two copies of each gene (one from each parent). MEN1 is autosomal dominant, meaning it only takes one parent with a gene mutation to pass it along.
That means offspring have a 50 percent chance of inheriting the mutated gene, according to the American Society of Clinical Oncology (ASCO). About 10 percent of those with a faulty MEN1 gene have no family history of the disease (they have what’s known as a de novo, or new mutation).
Type 2 is caused by a mutation in the RET gene. It, too, is involved in telling cells how to make protein—and the protein it provides instructions for is necessary for the normal development of the kidney and nerve cells, as well as for sperm production.
Like type 1, type 2 only requires one parent with a gene mutation. According to the ASCO, if either parent has the mutation, the child has a 50 percent chance of inheriting it. Type 2 also may be a de novo (new) mutation. The majority of people with MEN2B don’t have an inherited mutation. Meanwhile, fewer than 5 percent of people with MEN2A are thought to have a new mutation.
People with this condition develop tumors that produce extra hormones.
MEN1 typically involves tumors of the:
Most tumors in people with MEN1 are noncancerous. However, according to ASCO, one out of three pancreatic neuroendocrine and mediastinal neuroendocrine tumors are malignant. Special tumors of the gastrointestinal tract and carcinoid tumors are most likely to become malignant as well.
People with MEN1 also may have tumors not related to the endocrine system, including:
These tumors may develop at any age. Complications vary depending on the location and size of tumors.
MEN2 typically involves tumors of the:
Symptoms vary depending on which endocrine and nonendocrine glands are involved.
Adrenal tumors may cause:
Carcinoid tumors may cause:
Parathyroid tumors may cause:
Pituitary tumors may cause:
It’s important to note that not everyone develops every symptom.
As with most diseases, symptoms vary from person to person.
Medullary thyroid carcinoma symptoms include:
If the tumor remains small, the patient may not have symptoms.
PHEO symptoms include:
Parathyroid tumor symptoms include:
The earlier the diagnosis, the better. This allows the patient to be monitored for tumors and other symptoms before they become more serious.
Patients are likely to undergo genetic testing, which may be performed with a blood or saliva sample.
In up to one in four cases, genetic testing may not find a mutation—even though the patient is exhibiting symptoms of MEN, according to the National Institute of Diabetes and Digestive and Kidney Diseases. The patient may have MEN and an unknown mutation, or a mutation in a different gene. Doctors may look for other causes of the symptoms in this case.
Diagnosis depends on the presence of several symptoms. Patients are likely to be diagnosed with MEN1 if they have one of the following:
Doctors may diagnose MEN2 after finding:
For both type 1 and type 2, the patient is likely to need:
Some tumors also may need to be biopsied to determine whether they are benign or malignant.
Treatment requires a team of specialists working together to care for the patient’s needs. Members of this care team are likely to include:
There’s no cure for MEN1, but it’s possible to live a long and productive life with this disease. Doctors may need to monitor the patient’s tumors and provide treatment on an as-needed basis.
To monitor the disease, the patient may need regular screening tests, including:
Surgery also may be needed to remove tumors, or the patient may be given medication to suppress tumor growth or other problems.
Treatment depends on a number of factors, including:
The thyroid may be removed during a procedure known as a thyroidectomy. This is often a preventive step. Once it’s removed, the patient may need to take thyroid replacement supplements.
MEN2 PHPT (parathyroid tumors) may be treated with medication. Some people undergo surgery to remove the parathyroid gland. Some healthy tissue from the parathyroid gland may be replanted in the forearm, so the patient doesn’t develop post-op hypoparathyroidism, which requires treatment with calcium and vitamin D for the duration of life.
PHEO is also treated with removal of one or both of the adrenal glands. The patient may need chemotherapy and radiation as follow-up for any tumors that have spread or are malignant.
Genetic counseling also may be part of the treatment plan, helping patients and their families learn:
Genetic counseling also may help the patient weigh decisions that have to be made when given the results.