title: Acute and chronic regulation of circulating PTH: significance in health and in disease.
abstract: Circulating human parathyroid hormone (PTH) is immunoheterogenous. It is composed of 80% carboxyl-terminal (C) fragments and of 20% PTH(1-84). This composition contrasts with the biological activity of the hormone, which is only related to PTH(1-84), creating a paradox between circulating PTH composition and PTH bioactivity. PTH molecular forms are either secreted by the parathyroid glands or generated by the peripheral metabolism of PTH(1-84) in the liver. The kidney has a major role in the disposal of C-PTH fragments. Secretion of PTH molecular forms by the parathyroid glands is highly regulated under a variety of clinical conditions, suggesting that C-PTH fragments could exert some biological effects of their own. Recent data suggest that C-PTH fragments can exert biological actions opposite to those of PTH(1-84) by acting on a C-PTH receptor not yet cloned. They can decrease calcium concentration, phosphate excretion, bone resorption and 1,25(OH)₂ synthesis. The clinical implications of this new concept are reviewed.
authors.affiliation: Centre de Recherche, Centre Hospitalier de l'Université de Montréal-CRCHUM, Hôpital Saint-Luc, Department of Medicine, Université de Montréal, Montréal, Québec, Canada. rechcalcium.chum@ssss.gouv.qc.ca
authors.forename: Pierre
authors.initials: P
authors.lastname: D'Amour
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D006801:Humans; D006961:Hyperparathyroidism / Q000097:blood* / Q000378:metabolism; D007668:Kidney / Q000378:metabolism / Q000503:physiopathology; D010281:Parathyroid Hormone / Q000097:blood* / Q000378:metabolism / Q000502:physiology; D010446:Peptide Fragments / Q000097:blood / Q000378:metabolism / Q000502:physiology; D018016:Receptors, Parathyroid Hormone / Q000378:metabolism; D051437:Renal Insufficiency / Q000097:blood
chemical_list: D010281:Parathyroid Hormone; D010446:Peptide Fragments; D018016:Receptors, Parathyroid Hormone; D002118:Calcium