[Regulation of synthesis and secretion of parathyroid hormone (PTH) and of tumor hypercalcemia hormone (PTHrP)].
PTH is a peptidic hormone which regulates blood calcium level. The PTH gene has been characterized and has 3 exons and 3 introns. PTH is synthetized as a precursor (pre-pro-PTH). The sequence "pre" is the signal peptide. The role of the sequence "pro" is still unknown. Main factors which regulate PTH synthesis are the level of extra-cellular calcium, vitamin D, and to a lesser extent steroid hormones. Calcium is the main factor influencing PTH secretion. Very recently, a "calcium sensor" has been purified and cloned. It is present on the membrane of parathyroid cells and some specific agonists of these receptors are already purified and could modulate PTH secretion. PTH-RP is responsible of hypercalcemia of tumors and has structural homologies with PTH. But, whereas PTH is only secreted by parathyroid cells, PTH-RP is synthetized by several different cell types and seems to act as an autocrine factor. Two major questions are still unanswered: 1) Is there only one receptor for PTH and PTH-RP? Some studies concluded that there are probably at least 2 different receptors, 2) And what is the role of PTH-RP? Many effects have already been published: pth-RP is involved in placental physiology, keratinocyte differentiation, or vascular smooth cell relaxation.
Service de Néphrologie A, Hôpital Tenon, Paris.
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Peraldi
D000818:Animals; D005786:Gene Expression Regulation; D006801:Humans; D010281:Parathyroid Hormone / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D044162:Parathyroid Hormone-Related Protein; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics* / Q000378:metabolism
C470121:PTHLH protein, human; D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins
Régulation de la synthèse et de la sécrétion de l'hormone parathyroïdienne (PTH) et de l'hormone hypercalcémiante des tumeurs (PTHrP).