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

Your Mayo Clinic care team

Mayo Clinic specialists work as a team to listen, counsel and treat people who have MEN 1. Depending on your specific needs and related conditions, the team may include experts in endocrinology, endocrine surgery, gastroenterology, neurosurgery, oncology, interventional radiology, radiation oncology, chest (thoracic) surgery, liver (hepatobiliary) surgery, medical genetics and other areas if needed.

Advanced diagnosis methods

The diagnosis of MEN 1 includes gathering a thorough medical and family history, as well as a physical exam to look for signs and symptoms of excess hormones. Then, blood is drawn to check hormone levels, and imaging tests may be done to look for endocrine system tumors.

If someone has already been diagnosed with MEN 1, imaging tests may be done even if hormone levels aren't yet abnormal. Imaging tests may include magnetic resonance imaging (MRI), computerized tomography (CT) scan, positron emission tomography (PET) scan, nuclear medicine scans (for example, octreotide scintigraphy), endoscopic ultrasound of the pancreas and other scans.

Mayo Clinic offers a new imaging test, Ga-DOTATATE PET scanning, which isn't yet widely available. Ga-DOTATATE PET scanning is combined with either CT imaging or MRI. This type of test is very sensitive for endocrine system tumors.

Conditions and testing related to MEN 1 may include:

  • Pituitary tumors. At Mayo Clinic, monitoring for pituitary tumors in people with MEN 1 includes an MRI of the pituitary gland and measuring certain hormones in your blood. If MRI results are abnormal, your doctor may do other pituitary testing. Although pituitary tumors are benign, they can cause problems if they overproduce a hormone or grow large enough to put pressure on surrounding structures, which can result in pituitary hormone deficiency, headache or vision loss.

    The most common pituitary gland problem in MEN 1 is a small tumor that releases too much prolactin (prolactinoma). In women, prolactinomas can interfere with the menstrual cycle or cause breast discharge. They can cause infertility in men.

    Some types of pituitary tumors produce too much growth hormone. This can result in excessive growth of certain body parts in adults (acromegaly) or excess height and growth in children (gigantism). Other pituitary tumors secrete an excess amount of adrenocorticotropic hormone (ACTH), which in turn stimulates the adrenal glands to make more cortisol. When this form of the syndrome develops, it's called Cushing disease.

  • Hyperparathyroidism. Specialists diagnose overactive parathyroid glands (hyperparathyroidism) in people with MEN 1 based on parathyroid hormone and calcium levels. Almost all people with MEN 1 develop hyperparathyroidism.

    At Mayo Clinic, specialists use the latest technology for diagnosis, such as parathyroid sestamibi scanning with single-photon emission computerized tomography (SPECT) imaging; ultrasound, which may include fine-needle aspiration with parathyroid hormone measurement; and 4-D CT scanning.

  • Pancreatic and duodenal neuroendocrine tumors. Specialists may use blood tests to detect substances produced by tumors (tumor markers) in the blood of people with MEN 1. Sometimes these changes can be found before symptoms appear. Imaging is often done with CT or MRI using specialized procedures to detect small tumors in the pancreas.

    Mayo specialists may also use endoscopic ultrasound to detect endocrine tumors in the first part of the small intestine (duodenum) and the pancreas. Nuclear medicine scans, such as octreotide scintigraphy or Ga-DOTATATE PET scanning, may be used to confirm the presence and locations of pancreatic neuroendocrine tumors.

  • Other tumors and findings. Tumors may arise in the lungs, thymus gland (carcinoid tumors) and esophagus (leiomyoma). Doctors will usually perform periodic imaging tests of these areas. People with MEN 1 often have skin tumors; these are benign and should be removed only if they cause symptoms.

Treatment expertise

Mayo Clinic experts have a wealth of expertise in the latest interventions for the tumors associated with multiple endocrine neoplasia, type 1 (MEN 1) if they are in one area (localized) or if they have spread (metastasized).

Below are related conditions and their treatment options:

  • Pituitary tumors. Doctors may recommend surgery or drug therapy based on the type of pituitary tumor. Prolactin-producing tumors can often be successfully treated with medications alone. Doctors will recommend regular follow-up screening.
  • Hyperparathyroidism. Most people with MEN 1 will develop too much calcium in the blood (hypercalcemia) due to too much parathyroid hormone (hyperparathyroidism) by the time they reach age 50. This can lead to the development of kidney stones, osteoporosis and other symptoms. Regular screening for people at risk can detect hyperparathyroidism before complications occur.

    The most common treatment is surgery to remove 3.5 of the four parathyroid glands (subtotal parathyroidectomy). The half gland that's left can maintain normal levels of calcium. However, with time, the remaining parathyroid tissue usually starts to overproduce parathyroid hormone again.

    When re-treatment is required, options include a second surgery, transplantation of parathyroid tissue to the arm or chest wall, or alcohol injection into a portion of the parathyroid gland under ultrasound guidance.

  • Neuroendocrine tumors. People with MEN 1 frequently develop neuroendocrine tumors, also called islet cell tumors. These are usually located in the pancreas or small intestine (duodenum). These can become cancerous (malignant), so early detection and intervention is important. Some neuroendocrine tumors overproduce a normal pancreatic hormone, which results in symptoms related to high levels of the specific hormone. Treatment depends on the type and stage of the tumor.
  • Hypoglycemic syndrome. Some people with MEN 1 develop tumors that produce too much insulin (insulinomas). Although the tumors are most often not cancerous, they can cause severely low levels of glucose, which can be life-threatening. More than one tumor may be present, and doctors usually recommend surgery. In removing the tumor or tumors, often a portion of the normal pancreas needs to be removed.
  • Zollinger-Ellison syndrome (ZES). Many people with MEN 1 develop ZES, which involves tumors that result in overproduction of gastric acid (gastrinomas) leading to ulcers and diarrhea. Doctors may prescribe medication such as proton pump inhibitors. However, extensive surgery may be necessary to slow the progress of the disease.
  • Other pancreatic neuroendocrine tumors. Less commonly, pancreatic neuroendocrine tumors will produce other hormones. These include adrenocorticotropic corticotrophin (ACTH), which causes Cushing syndrome; vasoactive intestinal peptide, which causes watery diarrhea; and glucagon, which causes elevated blood sugar and a specific skin rash. Treatment of these types of tumors may involve medication, surgery or an ablation procedure.
  • Metastatic neuroendocrine tumors. If your disease is more advanced — for example, if it has spread to the lymph nodes or liver — treatment may involve liver surgery, radiofrequency ablation, cryoablation (freezing) or injection of strong chemotherapy drugs directly into the liver (chemoembolization). When surgery is not an option, doctors may use other forms of chemotherapy or hormone-based treatments.

    In the case of metastatic tumors, a multidisciplinary team of specialists is critical, as hormonal therapy, surgery, interventional radiology ablative procedures and chemotherapy are often used together or sequentially.

  • Adrenal tumors. Some people with MEN 1 develop tumors in their adrenal glands. Most tumors do not produce hormones and are not cancerous, so they can be observed and not treated. However, if the tumors produce hormones or they're large and thought to be cancerous, doctors recommend removing them, usually with laparoscopic surgery.
  • Carcinoid tumors. Carcinoid tumors in people with MEN 1 can develop in the lungs, thymus gland and gastrointestinal tract. Surgeons remove these tumors when they haven't spread to other areas. Doctors may use chemotherapy, radiation therapy or hormone-based therapy for advanced cases.

Genetic specialists

Mayo Clinic experts encourage people who have a MEN 1 genetic mutation to have periodic tests to look for tumors and other related medical problems. Experts recommend that family members at risk of MEN 1 get genetic testing or start getting clinical screening in childhood or the early teen years because problems, such as hyperparathyroidism, can develop before the age of 20. Screening can begin as early as 5 years old.

At Mayo Clinic, genetic specialists from the Department of Clinical Genomics will help you review the pros and cons of genetic testing. At this meeting, you can learn:

  • How and where the test is performed
  • The probability of a positive test
  • How a positive test would influence current medical management
  • How a positive test would provide options for at-risk family members
  • Which family members might be at risk and need further evaluation

Genetic testing may determine whether someone has a genetic mutation causing MEN 1. If someone has a mutation, his or her children are at risk of inheriting the mutation and developing MEN 1. Parents and siblings also are at risk of having the mutation even if they have not yet developed symptoms.

If no related genetic changes are found in family members, then no further screening tests are needed. However, genetic testing doesn't uncover all MEN 1 genetic mutations. If genetic testing doesn't confirm MEN 1, but it's likely a person has it, that person, as well as family members, still needs close follow-up with appropriate blood tests and diagnostic imaging.

Expertise and rankings


Multiple endocrine neoplasia, type 1 (MEN 1) is a rare condition, affecting about 1 in 30,000 people. Mayo Clinic specialists treat about 140 people with MEN 1 each year.


Mayo Clinic scientists are working to improve the diagnosis and treatment of multiple endocrine neoplasia, including the treatment of recurrent parathyroid tumors with percutaneous ethanol ablation, better detection of uncommon carcinoid and neuroendocrine tumors, new chemotherapy drugs, and other interventional radiology ablative procedures.

Mayo Clinic in Rochester, Minn., ranks No. 1 for diabetes and endocrinology in the U.S. News & World Report Best Hospitals rankings. Mayo Clinic in Phoenix/Scottsdale, Ariz., and Mayo Clinic in Jacksonville, Fla., are ranked among the Best Hospitals for diabetes and endocrinology by U.S. News & World Report.

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Nov. 16, 2018


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