title: Influence of glomerular filtration rate on non-(1-84) parathyroid hormone (PTH) detected by intact PTH assays.
abstract: BACKGROUND
  Commercial intact parathyroid hormone (I-PTH) assays detect molecular form(s) of human PTH, non-(1-84) PTH, different from the 84-amino acid native molecule. These molecular form(s) accumulate in hemodialyzed patients. We investigated the importance of non-(1-84) PTH in the interpretation of the increased I-PTH in progressive renal failure.
  
  
  METHODS
  Five groups were studied: 26 healthy individuals, 12 hemodialyzed patients, and 31 patients with progressive renal failure subdivided according to their glomerular filtration rate (GFR) into 11 with a GFR between 60 and 100 mL. min(-1). 1.73 m(-2), 12 with a GFR between 30 and 60 mL. min(-1). 1.73 m(-2), and 8 with a GFR between 5 and 30 mL. min(-1). 1.73 m(-2). We evaluated indicators of calcium and phosphorus metabolism and creatinine clearance (CrCl) in the progressive renal failure groups, and the HPLC profile of I-PTH and C-terminal PTH in all groups.
  
  
  RESULTS
  Only patients with a GFR <30 mL. min(-1). 1.73 m(-2) and hemodialyzed patients had decreased Ca(2+) and 1,25-dihydroxyvitamin D, and increased phosphate. In patients with progressive renal failure, I-PTH was related to Ca(2+) (r = -0.66; P <0.0001), CrCl (r = -0.61; P <0.001), 1,25-dihydroxyvitamin D (r = -0.40; P <0.05), and 25-hydroxyvitamin D (r = -0.49; P <0.01) by simple linear regression. The importance of non-(1-84) PTH in the composition of I-PTH increased with each GFR decrease, being 21% in healthy individuals, 32% in progressive renal failure patients with a GFR <30 mL. min(-1). 1.73 m(-2), and 50% in hemodialyzed patients, with PTH(1-84) making up the difference.
  
  
  CONCLUSIONS
  As I-PTH increases progressively with GFR decrease, part of the increase is associated with the accumulation of non-(1-84) PTH, particularly when the GFR is <30 mL. min(-1). 1.73 m(-2). Concentrations of I-PTH 1.6-fold higher than in healthy individuals are necessary in hemodialyzed patients to achieve PTH(1-84) concentrations similar to those in the absence of renal failure.
authors.affiliation: Centre de Recherche et, Hôpital Saint-Luc, Montreal, Quebec H2X 1P1, Canada.
authors.forename: J H
authors.initials: JH
authors.lastname: Brossard
authors.forename: R
authors.initials: R
authors.lastname: Lepage
authors.forename: H
authors.initials: H
authors.lastname: Cardinal
authors.forename: L
authors.initials: L
authors.lastname: Roy
authors.forename: L
authors.initials: L
authors.lastname: Rousseau
authors.forename: C
authors.initials: C
authors.lastname: Dorais
authors.forename: P
authors.initials: P
authors.lastname: D'Amour
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007118:Immunoassay; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood* / Q000737:chemistry; D006435:Renal Dialysis; D051437:Renal Insufficiency / Q000097:blood* / Q000503:physiopathology* / Q000628:therapy
chemical_list: D010281:Parathyroid Hormone