Multiple endocrine adenomatosis syndromes.

MEA I and II are two genetically distinct tumor endocrinopathies, both showing autosomal dominant inheritance. Little overlap exists between these conditions, and that which is present can be explained on the basis of two mutually exclusive factors: (1) the secondary consequences of hormone excess on another endocrine gland or (2) the fact that both tumor syndromes appear to result from genetically faulty differentiation of neuroectoderm. A seemingly disproportionate amount of effort has been expended on study of the MEA syndromes. However, there would seen to be ample justification for this interest: 1) The MEA syndromes, unlike most neoplastic conditions, are hereditary and can be readily detected and more expeditiously treated; 2) hormone radioimmunoassay has greatly facilitated diagnosis in asymptomatic individuals; and (3) probably most importantly, study of these syndromes has provided considerable insight into the embryologic origin of the endocrine system. It is conceivable that knowledge gained from these conditions may stimulate further inquiry into the processes whereby neoplasia occurs in endocrine tissue and thus lead the way to the development of effective therapy for a host of hormone-producing tumors.