Bone resorption in kidney transplant recipients.

Early diagnosis of persistent hyperparathyroidism (HP) following kidney transplantation may prevent worsening of osteodystrophy and potential damage to the graft. We evaluated the utility of collagen pyridinoline (PYD) and deoxypyridinoline (DPD) urinary cross-links beyond the common HP markers to evaluate 70 selected stable recipients between 1997 and 2006 who were divided into 2 group depending on the immunosuppressive protocol. All patients showed elevated levels of urinary cross-links even though calcemia and phosphoremia values were normal. Their mean creatinine level was slightly increased. Data were assessed as mean values +/- SD. All variables underwent a correlation matrix analysis and a stepwise regression, with posttransplant intact parathyroid hormone (iPTH) as the dependent variable and other variables as regressors. A statistically significant correlation was observed between PYD and alkaline phosphatase (ALP; P = .0026, r = .41); PYD and DPD (P = .015, r = .34); pre- and posttransplant iPTH (P = .024, r = .31); and creatinine and ALP (P = .024, r = .31). Taking the groups separately, there were significant correlations between PYD and ALP (P = .0076, r = .42); PYD and DPD (P = .017, r = .38); ALP and posttransplant iPTH (P = .038, r = .33); osteocalcin (OC) and posttransplant iPTH (P = .048, r = .32); and pre- and posttransplant iPTH (P = .019, r = .37) among subjects in the first group, whereas subjects in the second group showed a correlation between posttransplant iPTH and age at transplantation (P = .032, r = .61). In conclusion, we showed that urinary cross-links may be helpful to reveal bone resorption in kidney recipients when usual bone metabolism parameters do not demonstrate hyperparathyroidism.