[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Conditions](https://durgical.com/en/conditions/) › Multiple endocrine neoplasia (MEN 1, 2A, 2B)

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# Multiple endocrine neoplasia (MEN 1, 2A, 2B)

Inherited syndromes in which tumours grow in several hormone glands. Gene testing of the family allows early surgery that prevents cancer.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Parathyroid glands](https://durgical.com/en/anatomy/parathyroid-glands/)
- [Pituitary gland](https://durgical.com/en/anatomy/pituitary-gland/)
- [Pancreas](https://durgical.com/en/anatomy/pancreas/)
- [Thyroid gland](https://durgical.com/en/anatomy/thyroid-gland/)
- [Right adrenal gland](https://durgical.com/en/anatomy/suprarenal-gland-abdomen/)
- [Left adrenal gland](https://durgical.com/en/anatomy/suprarenal-gland/)
- [Duodenum](https://durgical.com/en/anatomy/duodenum/)

## In embryology

- [Pharyngeal pouches: tonsil, thymus, parathyroids and C cells](https://durgical.com/en/embryology/pharyngeal-pouches-tonsil-thymus-parathyroids-and-c-cells/)

## Why it happens

- [Tumour suppressor genes: RB, TP53, APC, BRCA and the two-hit hypothesis](https://durgical.com/en/general-pathology/tumour-suppressor-genes-rb-tp53-apc-brca-and-the-two-hit-hypothesis/)
- [Oncogenes: RAS, MYC, HER2, BCR-ABL and the table to know](https://durgical.com/en/general-pathology/oncogenes-ras-myc-her2-bcr-abl-and-the-table-to-know/)
- [Hereditary cancer syndromes: the table to know](https://durgical.com/en/general-pathology/hereditary-cancer-syndromes-the-table-to-know/)
- [Receptor tyrosine kinases](https://durgical.com/en/biochemistry/topics/receptor-tyrosine-kinases/)
- [Thyroid follicles, C cells and parathyroid](https://durgical.com/en/histology/thyroid-follicles-c-cells-and-parathyroid/)
- [Adrenal cortex zones and medulla](https://durgical.com/en/histology/adrenal-cortex-zones-and-medulla/)

## What it is

A group of autosomal dominant syndromes in which tumours develop in two or more endocrine glands. MEN 1 (MEN1 gene, menin) involves the parathyroids, [pancreas](https://durgical.com/en/anatomy/pancreas/) and [duodenum](https://durgical.com/en/anatomy/duodenum/), and pituitary; MEN 2A and 2B (RET proto-oncogene) involve medullary thyroid carcinoma and pheochromocytoma, with hyperparathyroidism in 2A and mucosal neuromas in 2B.

## Who gets it

Rare, but important in practice because carriers in a family can be identified by genetic testing. Medullary thyroid carcinoma develops in almost all RET carriers; primary hyperparathyroidism is the most frequent and earliest feature of MEN 1.

## Causes

- MEN 1: inactivating mutation of the MEN1 tumour-suppressor gene (menin) on chromosome 11
- MEN 2A and 2B: activating mutations of the RET proto-oncogene on chromosome 10
- Autosomal dominant inheritance with high penetrance; some cases are new mutations

## Risk factors

- A first-degree relative with MEN or with a known MEN1 or RET mutation
- Hyperparathyroidism at a young age or with multigland disease
- Medullary thyroid carcinoma or bilateral pheochromocytoma at any age

## Pathophysiology

In MEN 1, loss of the second normal copy of a tumour-suppressor gene allows multiple tumours to grow in the target glands. In MEN 2, a constantly active RET receptor drives hyperplasia of thyroid C cells and adrenal medullary cells, which progresses to medullary carcinoma and pheochromocytoma. Symptoms come from excess hormones (calcium, gastrin, insulin, prolactin, catecholamines, calcitonin) and from local tumour growth.

## Classification

- MEN 1 (the three Ps): parathyroid hyperplasia or adenomas, pancreatic and duodenal neuroendocrine tumours (gastrinoma, insulinoma), pituitary adenomas (often prolactinoma)
- MEN 2A: medullary thyroid carcinoma, pheochromocytoma and parathyroid hyperplasia
- MEN 2B: medullary thyroid carcinoma, pheochromocytoma, mucosal neuromas and a marfanoid habitus

## Symptoms and signs

- Hypercalcaemia: [kidney](https://durgical.com/en/anatomy/kidney/) stones, bone pain, abdominal pain, polyuria and fatigue
- Gastrinoma: recurrent or multiple peptic ulcers and chronic diarrhoea (Zollinger-Ellison syndrome)
- Insulinoma: fasting hypoglycaemia with confusion or sweating
- Pituitary tumour: amenorrhoea, galactorrhoea, acromegaly or visual field defects
- Pheochromocytoma: episodic headache, sweating, palpitations and hypertension
- Medullary thyroid carcinoma: thyroid nodule or [neck lymph nodes](https://durgical.com/en/anatomy/lymph-nodes-of-neck/); diarrhoea in advanced disease

## Red flags

- Hypertensive crisis, especially during surgery or anaesthesia (undiagnosed pheochromocytoma)
- Severe hypoglycaemia
- Gastrointestinal bleeding or perforation from ulcers
- Rapidly growing neck mass or lymph nodes

## Diagnosis

**Clinical**
Suspected when two of the characteristic tumours occur in one person, or one occurs in a relative of a known case. A careful family history is essential.

**Tests**
Genetic testing for MEN1 or RET mutations in index cases and relatives. Calcium and PTH; gastrin, fasting glucose with insulin, prolactin and IGF-1 in MEN 1; calcitonin and CEA for medullary carcinoma; plasma or urine metanephrines for pheochromocytoma.

**Imaging**
Pituitary MRI; pancreatic CT, MRI, endoscopic ultrasound or somatostatin receptor PET; neck ultrasound; adrenal CT or MRI.

## Differential diagnosis

- Sporadic primary hyperparathyroidism
- Sporadic pituitary adenoma or neuroendocrine tumour
- Von Hippel-Lindau disease and neurofibromatosis type 1 (other syndromes with pheochromocytoma)
- Familial hypocalciuric hypercalcaemia

## Goal of treatment

Detect tumours early in carriers, remove or control them before they spread or cause hormonal emergencies, and screen relatives.

## Treatment

**Surgical**
Prophylactic total thyroidectomy in RET carriers, timed by the risk level of the specific mutation (in early childhood for MEN 2B).

**Surgical**
Pheochromocytoma is removed before any thyroid or other surgery, after alpha-blockade. Subtotal or total parathyroidectomy for hyperparathyroidism; resection of selected pancreatic tumours.

**Medical**
Proton pump inhibitors for gastrinoma, dopamine agonists for prolactinoma, and somatostatin analogues for some neuroendocrine tumours.

**Follow-up**
Lifelong biochemical and imaging surveillance of carriers, and genetic counselling and testing of first-degree relatives.

## Complications

- Metastatic medullary thyroid carcinoma
- Malignant pancreatic neuroendocrine tumours, a leading cause of death in MEN 1
- Hypertensive crisis from pheochromocytoma
- Recurrent hyperparathyroidism and kidney stones
- Hypoparathyroidism after parathyroid surgery

## Prognosis

Depends on which tumours develop and when they are found. Early genetic diagnosis with prophylactic thyroidectomy has greatly improved survival in MEN 2; in MEN 1, malignant neuroendocrine tumours largely determine outcome.

## Prevention

- Genetic testing of relatives of affected individuals
- Prophylactic thyroidectomy in RET mutation carriers

## Test yourself

Think of the answer, then tap the question to see it.

## Which three glands are classically affected in MEN 1?

Parathyroid, pancreas (and duodenum) and pituitary: the three Ps.

## Which gene is mutated in MEN 2A and 2B?

The RET proto-oncogene, with an activating (gain-of-function) mutation.

## In MEN 2, which tumour must be excluded and treated before thyroid surgery?

Pheochromocytoma, to avoid a hypertensive crisis during anaesthesia.

## Which features distinguish MEN 2B from MEN 2A?

Mucosal neuromas and a marfanoid habitus, with no hyperparathyroidism.

## What is the most common feature of MEN 1?

Primary hyperparathyroidism from multigland parathyroid hyperplasia.

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## Related conditions

- [Primary hyperparathyroidism](https://durgical.com/en/conditions/primary-hyperparathyroidism/)
- [Pituitary adenoma](https://durgical.com/en/conditions/pituitary-adenoma/)
- [Prolactinoma (hyperprolactinaemia)](https://durgical.com/en/conditions/prolactinoma/)
- [Zollinger-Ellison syndrome (gastrinoma)](https://durgical.com/en/conditions/zollinger-ellison-syndrome/)
- [Insulinoma](https://durgical.com/en/conditions/insulinoma/)
- [Medullary thyroid carcinoma](https://durgical.com/en/conditions/medullary-thyroid-carcinoma/)
- [Phaeochromocytoma](https://durgical.com/en/conditions/phaeochromocytoma/)
- [Thyroid cancer (papillary)](https://durgical.com/en/conditions/thyroid-cancer/)
- [Marfan syndrome](https://durgical.com/en/conditions/marfan-syndrome/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Multiple endocrine neoplasia (MEN) I](https://medlineplus.gov/ency/article/000398.htm) (MedlinePlus Medical Encyclopedia (U.S. National Library of Medicine), 2025); [Multiple endocrine neoplasia (MEN) II](https://medlineplus.gov/ency/article/000399.htm) (MedlinePlus Medical Encyclopedia (U.S. National Library of Medicine), 2025).

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Source: https://durgical.com/en/conditions/multiple-endocrine-neoplasia/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/multiple-endocrine-neoplasia/