Urinary deoxypyridinoline excretion for the evaluation of bone turnover inchronic renal failure

Background: The urinary excretion of deoxypyridinoline (DPD) was evaluated in predialysis chronic renal failure (CRF), together with intact PTH and se veral classic markers of bone turnover in order to assess whether urine fre e and total DPD excretion are equivalent parameters of bone turnover in CRF , and to evaluate the relationship between urine DPD excretion, PTH and the other bone markers. Methods: The study was carried out in 94 patients with different deg rees of renal failure due to various kidney diseases. Beside s urinary DPD expressed as free DPD, total DPD, free/total DPD, free DPD/Cr and total DPD/Cr, the following determinations were made: intact PTH, bone alkaline phosphatase (BALP), total alkaline phosphatase (AP), osteocalcin (BGP), serum C-terminal telopeptide of collagen type I (ICTP) and hydroxypr oline (OHpro). The patients were divided into 3 groups according to the inc reasing severity of renal failure (Ccr >40, 40-20, <20 ml/min). Results: Th e ratio free/total DPD decreased (NS) with advancing renal failure, and was inversely correlated with total DPD excretion. While PTH increased progres sively to about four times the values observed in the Ccr >40 group, there was a parallel increase only in BGP and ICTP, parameters retained in the se rum with decreasing renal function, while AP, BALP, total DPD and OHpro did not change. However, significant correlations between total DPD/Cr and PTH , BALP, BGP and ICTP were also found. Conclusions: In CRF free DPD is an un reliable index of bone turnover due to a probable interference in its produ ction from the peptide-bound DPD. Total DPD or total DPD/Cr are better used . In spite of the significant correlations observed in advanced renal failu re between PTH and most of the parameters examined, a resistance of bone ti ssue to PTH action in CRF must be considered. Copyright (C) 2000 S. Karger AG, Basel.