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: J H Brossard, R Lepage, H Cardinal, L Roy, L Rousseau, C Dorais, P D'Amour
• Journal: Clinical chemistry (Clin Chem) Vol. 46 Issue 5 Pg. 697-703 (May 2000) ISSN: 0009-9147 [Print] England
• PMID: 10794753 (Publication Type: Clinical Trial, Journal Article)

Chemical References

• Parathyroid Hormone

Topics

• Adult
• Aged
• Female
• Glomerular Filtration Rate
• Humans
• Immunoassay
• Male
• Middle Aged
• Parathyroid Hormone (blood, chemistry)
• Renal Dialysis
• Renal Insufficiency (blood, physiopathology, therapy)