title: The two-hit theory of neoplasia: implications for the pathogenesis of hyperparathyroidism.
abstract: Knudson's two-hit or two-mutational-event hypothesis for the initiation of neoplasia suggests that two somatic mutations are necessary for initiation of sporadic neoplasms, and that a genetic plus a somatic mutation are required for hereditary neoplasms. Glucose-6-phosphate dehydrogenase (G6PD) studies of parathyroid tumors of 11 heterozygotes with hyperparathyroidism (HPT), including one with hereditary HPT, have shown both A and B isoenzymes. These findings suggest multicellular development of parathyroid tumors and are compatible with tumors being manifestations of either nonneoplastic hyperplasia or a genetic first mutational event. Parathyroid carcinoma may be the result of a second mutation in cells made susceptible by previous genetic or somatic mutations. Comparison of parathyroid cancer in families with hereditary HPT with sporadic cases from the literature reveals a generally younger onset with hereditary HPT compatible with the two-hit theory. Consideration of these age-of-onset and G6PD findings suggest that hyperparathyroidism may result from either non-neoplastic or mutational-induced processes even though no histologic distinctions have been observed in the hyperplasia associated with these processes.
mesh_terms: D005954:Glucosephosphate Dehydrogenase / Q000235:genetics; D006801:Humans; D006961:Hyperparathyroidism / Q000150:complications / Q000235:genetics* / Q000473:pathology; D008957:Models, Genetic; D009154:Mutation; D010282:Parathyroid Neoplasms / Q000150:complications / Q000201:enzymology / Q000235:genetics* / Q000473:pathology
chemical_list: D005954:Glucosephosphate Dehydrogenase