Clinical features of multiple endocrine neoplasia type 1 and type 2.

The term 'Multiple Endocrine Neoplasia' (MEN) denotes a genetically determined syndrome characterized by the independent appearance of benign or malignant changes of several endocrine organs as well as occasional changes of neural, muscular and connective tissue. Three different forms have been identified: MEN 1 (Werner's syndrome) includes parathyroid hyperplasia in combination with pancreatic islet cell and pituitary tumours; MEN 2a (Sipple's syndrome) includes medullary thyroid carcinoma in association with phaeochromocytoma and parathyroid hyperplasia; MEN 2b includes medullary thyroid carcinoma, phaeochromocytoma and mucosal neuromas. MEN syndrome is transmitted as an autosomal dominant trait with a high degree of penetrance. The changes in the individual glands appear to be causally and temporally independent of each other. A spectrum of pathological changes exist in the affected glands which range from hyperplasia to adenoma to carcinoma. The pathological process is almost always multicentric, often resulting in bilateral disease of organs. The appearance of an endocrine tumour known to be associated with MEN should alert the physician to the possibility of a MEN syndrome. When the possibility of such a syndrome exists, screening and long-term observation should be initiated to diagnose a carcinoma in its earliest stage, or before the development of clinical manifestations of hormone excess.