An evaluation of 1-84 PTH measurement in relation to bone alkaline phosphatase and bone Gla protein in hemodialysis patients.
OBJECTIVE
It has been suggested that higher levels of parathyroid hormone (PTH) are required to maintain normal bone turnover in chronic hemodialysis (HD) patients. Serum PTH levels determined by intact PTH (i-PTH) assay may overestimate the actual activity of circulating PTH in HD patients. The aim of the present study was to assess the clinical usefulness of whole PTH assay on the evaluation of bone turnover in HD patients.


METHODS
We performed measurement of parameters on bone turnover in 179 HD patients (116 men, 63 women; mean age 61.0 +/- 13.1 years). Serum whole PTH levels were determined as cyclase-activating PTH (CAP) by an immunoradiometric assay, and compared with those of i-PTH. Cyclase-inactivating PTH (CIP) was calculated as (i-PTH-CAP). The correlations between serum whole PTH levels and clinical parameters such as serum levels of Ca, P, bone alkaline phosphatase (BAP), bone Gla protein (BGP), total protein (TP), albumin (Alb), urea nitrogen (SUN), and creatinine (Cr) were analyzed using multivariate analysis.


RESULTS
The mean values of i-PTH and CAP were 124.1 +/- 97.4 and 86.9 +/- 71.6 pg/ml, respectively, indicating that the serum CAP levels were about 70% of i-PTH levels. The serum CAP levels significantly correlated with that of i-PTH (r = 0.959, p < 0.001). Moreover, a significant positive correlation between serum CAP levels and metabolic bone markers such as BAP (r = 0.400, p < 0.01) and BGP (r = 0.481, p < 0.01) was observed. Stepwise multivariate analysis revealed that serum levels of CAP were significantly determined by serum levels of Ca, P, Alb, and oral dosage of vitamin D (F ratio = 18.81, adjusted r(2) = 0.302).


CONCLUSIONS
These data suggest that the biological activity of circulating PTH in HD patients is lower than the levels estimated by conventional i-PTH assay.
Miwa
Naoko
N
Department of Medicine, Kidney Center, Tokyo Women's Medical University, Shinjuku-ku, Tokyo, Japan. miwa@kc.twmu.ac.jp
Nitta
Kosaku
K
Kimata
Naoki
N
Watanabe
Yoshihiko
Y
Suzuki
Koichi
K
Kawashima
Akira
A
Haga
Masahiro
M
Watanabe
Ryo-ichiro
R
Aoki
Takanao
T
Akiba
Takashi
T
Nihei
Hiroshi
H
D000469:Alkaline Phosphatase / Q000378:metabolism*; D016723:Bone Remodeling / Q000502:physiology; D001842:Bone and Bones / Q000201:enzymology* / Q000378:metabolism / Q000502:physiology; D002118:Calcium / Q000097:blood; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D016326:Extracellular Matrix Proteins; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D010758:Phosphorus / Q000097:blood; D006435:Renal Dialysis / Q000009:adverse effects; D000097568:Matrix Gla Protein
D000469:Alkaline Phosphatase; D002118:Calcium; D002135:Calcium-Binding Proteins; D016326:Extracellular Matrix Proteins; D010281:Parathyroid Hormone; D010758:Phosphorus; D000097568:Matrix Gla Protein