title: IRMA (whole PTH) is a more useful assay for the effect of PTH on bone than the Allegro intact PTH assay in CAPD patients with low bone turnover marker.
abstract: The common intact parathyroid hormone (i-PTH) assay detects not only PTH (1-84) but also the PTH (7-84) fragment. Recently, it was reported that the PTH (7-84) fragment is an antagonist to the biological action of PTH (1-84). It was also reported that the accumulation of the PTH (7-84) fragment plays a role in skeletal resistance in haemodialysis (HD) patients. However, the role of accumulation of the PTH (7-84) fragment in continuous ambulatory peritoneal dialysis (CAPD) patients, with a different clearance rate from that of HD patients, is still unclear. Therefore, we have measured only the active form of PTH (1-84) using a new method of whole PTH (w-PTH) assay in 20 CAPD patients (15 male and five female; mean age 51.0+/-13.0 years). The mean w-PTH value was 88.5 +/-14.2 pg/ml in CAPD patients, which was 42.1% of i-PTH (152.6+/-23.6 pg/ml). The approximate value of w-PTH was calculated using the following formula (w-PTH=0.58 x iPTH-0.4, R(2)=0.94). PTH (7-84) fragment was calculated by the formula i-PTH-w-PTH. The PTH (7-84) fragment/w-PTH ratio as an index of skeletal resistance, and serum alkaline phosphatase activity as an osteoblastic marker were negatively correlated (P=0.02). From these results, we concluded that the i-PTH level as calculated using the common assay method might lead to an overestimation of parathyroid function and bone turnover in CAPD patients similarly to HD patients. The w-PTH assay may be useful for more precise evaluation of PTH activity in end-stage renal disease patients.
authors.affiliation: The Division of Kidney and Hypertension, Jikei University School of Medicine, Tokyo, Japan. tanno@jikei.ac.jp
authors.forename: Yudo
authors.initials: Y
authors.lastname: Tanno
authors.forename: Keitaro
authors.initials: K
authors.lastname: Yokoyama
authors.forename: Masaaki
authors.initials: M
authors.lastname: Nakayama
authors.forename: Akihiko
authors.initials: A
authors.lastname: Katoh
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Iwasaki
authors.forename: Tom
authors.initials: T
authors.lastname: Cantor
authors.forename: Masafumi
authors.initials: M
authors.lastname: Fukagawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Shigematsu
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Hosoya
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000032:analysis; D016723:Bone Remodeling / Q000502:physiology*; D001842:Bone and Bones / Q000502:physiology*; D005260:Female; D006801:Humans; D015592:Immunoradiometric Assay / Q000592:standards; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000032:analysis* / Q000502:physiology*; D010531:Peritoneal Dialysis, Continuous Ambulatory; D011863:Radioimmunoassay / Q000379:methods* / Q000592:standards
chemical_list: D015415:Biomarkers; D010281:Parathyroid Hormone