Recent advances in multiple endocrine neoplasia syndromes.

The MEN syndrome are autosomal-dominant disorders of endocrine tissues, characterized by tumor development and in many instances, hormonal hypersecretory states. The genetic lesion in MEN I appears to involve a tumor suppressor locus on the long arm of chromosomes 11 but the identity of the affected gene and its role in contributing to dysregulation of endocrine cell function remain unknown. The lesion in MEN II has been localized to the RET protooncogene locus in the pericentromeric region of chromosome 10. This putative single transmembrane-domain, tyrosine kinase-linked receptor is selectively mutated to produce a constitutively activated protein and presumably an undampened growth-promoting signal to the target cell. Additional studies focused on these genes and their products should facilitate the screening and treatment of patients affected with these disorders and, potentially, provide more information about the role that these genes play in the normal growth and development of endocrine tissues. Such information should prove valuable in deciphering the pathogenetic mechanisms underlying the development of the more common sporadic endocrine tumors.