[Concept, etiology and epidemiology of primary hyperparathyroidism].
Primary hyperparathyroidism (PHPT) is one of the most frequent endocrinological disorders. In PHPT, there is abnormal regulation of parathyroid hormone (PTH) by calcium, which translates into inappropriately high PTH secretion for the level of calcemia. Most patients with PHPT have increased serum PTH levels, with increases in serum calcium, especially ionic calcium. The incidence of PHPT rises with age, the mean age at diagnosis being 55 years. This disorder affects mainly women with a female-to-male ratio of approximately 3:1. Most (80-85%) of cases are produced by chief cell parathyroid adenomas. The factors involved in the genesis of PHPT are largely unknown. Gene mutations affecting oncogenes (cyclin D1, RET) or tumor suppressor genes (MEN1, HRPT2) are found in a minority of cases. These mutations are especially important in familial forms of PHPT, such as multiple endocrine neoplasia syndrome (MEN1, MEN2A). No mutations affecting the calcium-sensing receptor (CaSR) or vitamin D receptor (VDR) gene have been found. In parathyroid adenomas and hyperplasias, there may be abnormal Wnt signalling, with mutations of the coreceptor LRP5 gene and beta-catenin accumulation. Expression of the Klotho protein, which intervenes in serum calcium regulation, is reduced. Low levels of 25(OH) vitamin D frequently coexist, although whether vitamin D deficiency plays a pathogenic role in PHPT is unknown.
Martínez Díaz-Guerra
Guillermo
G
Servicio de Endocrinología y Nutrición, Hospital Universitario 12 de Octubre, Madrid, España. gmdiazguerra@gmail.com
Hawkins Carranza
Federico
F
D006801:Humans; D049950:Hyperparathyroidism, Primary / Q000453:epidemiology* / Q000209:etiology*