Multiple endocrine neoplasia (MEN) syndromes.

Multiple endocrine neoplasia (MEN) syndromes are characterised by the combined occurrence of two or more endocrine tumours in a patient. These autosomal dominant conditions occur in four types: MEN1 due to inactivating MEN1 mutations; MEN2A and MEN2B (MEN3) due to activating mutations of RET and MEN4 due to inactivating cyclin-dependent kinase inhibitor 1B (CDKN1B) mutations. Each MEN syndrome exhibits different combinations of pancreatic islet, anterior pituitary, parathyroid, medullary thyroid and adrenal tumours. This article provides an overview of the clinical features, treatments and molecular genetics of each endocrine tumour syndrome.