Multiple Endocrine Neoplasia Type I

Also known as: Wermer syndrome


Multiple endocrine neoplasia type I (MEN I) is a rare genetic condition in which tumours (see entry Cancer) develop in one or more of the endocrine glands. Endocrine glands release hormones (chemical messages) into the bloodstream. The endocrine glands most commonly involved in MEN I include:

  • pancreas
  • parathyroid
  • pituitary
  • adrenal.

The age of onset of MEN I is usually in the teenage years, although symptoms may not appear for several years.


Last updated October 2018 by Professor RV Thakker, Academic Endocrine Unit, University of Oxford, Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Churchill Hospital, Oxford, UK.

Although great care has been taken in the compilation and preparation of all entries to ensure accuracy, we cannot accept responsibility for any errors or omissions. Any medical information provided is for education/information purposes and is not designed to replace medical advice by a qualified medical professional.

What are the symptoms?

The majority of tumours in MEN I are slow growing and benign (non-cancerous). They can affect:

  • Parathyroid gland – controls calcium in the blood, bones and urine. Hyperparathyroidism (over-activity of the parathyroid gland) is associated with high levels of calcium in the blood (hypercalcaemia). This can cause tiredness, weakness, muscle or bone pain, indigestion, kidney stones or thinning of the bones, poor memory, irritability, ulcers and bone fractures.
  • Pancreatic islet cells – release hormones that help with digestion and metabolism of nutrients, such as glucose. Tumours in the pancreatic islet cells are associated with the release of excessive amounts of hormones such as gastrin or insulin. Over-secretion of gastrin is associated with formation of severe ulcers in the stomach and small intestine which may cause severe vomiting with blood and/or diarrhoea. If left untreated, these may cause rupture of the stomach or intestine. Over secretion of insulin is associated with a low blood glucose that can cause feeling hungry and sweaty, and if severe then unconsciousness and fits.
  • Pituitary gland – plays a critical role in regulating growth and development, metabolism and reproduction. It releases prolactin, growth hormone and other key hormones. Symptoms associated with tumours in the pituitary gland include a loss or irregularity of the menstrual cycle, headaches, high blood pressure and eye problems.
  • Adrenal gland – plays a critical role in regulating salt and water balance, and in combatting stress.  It releases steroids and catecholamines (such as adrenaline).  The tumours usually do not release hormones and when they do, these are usually steroids, whose excess results in weight gain and symptoms associated with high blood pressure and diabetes.

What are the causes?

Changes (mutations) in a gene on chromosome 11 (known as MEN I) cause MEN I. The condition causes tumours of various glands to appear in the same person, but not necessarily at the same time.

How is it diagnosed?

A diagnosis of MEN I is made when either:

  • a patient has two or more MEN I associated growths
  • a patient has only one growth, but there exists a family history of relatives with MEN I.
  • An unaffected individual is found to have a change (mutation) in the MEN1 gene.

Initial screening for most of the tumours associated with MEN I includes the monitoring of hormone levels using blood tests and scans of the head, neck and abdominal area.

How is it treated?

Surgery to remove the affected gland is the most effective treatment. Medicines that prevent the release of: prolactin and growth hormone may be used instead of surgery for pituitary tumours; and of gastrin for pancreatic tumours oversecreting gastrin.

Hormone replacement therapy is given when entire glands are removed or do not produce enough hormones.

Inheritance patterns and prenatal diagnosis

Inheritance patterns
MEN I is inherited as an autosomal dominant trait. Affected families should be referred to a genetics centre for information and advice.

Prenatal diagnosis
This is possible if the genetic mutation in a family has been identified.

Is there support?

AMEND (Association for Multiple Endocrine Neoplasia Disorders)

Tel: 01892 516076

The Organisation is a Registered Charity in England and Wales No. 1099796, established in 2002. It is a patient support group run by volunteers for the benefit of everyone affected by multiple endocrine neoplasia disorders and their associated endocrine growths. The Organisation runs a UK research registry and produces patient information with the help of an expert medical advisory team, including information for children. Membership is free and open to patients and health professionals.

Group details last confirmed October 2018.

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