Osteoprotegerin (OPG), a member of the TNF receptor superfamily is a natural inhibitor of osteoclastogenesis and important inhibitor of vascular calcification. The aim of the study was to estimate a correlation of serum OPG level and the other parameters calcium-phosphorus metabolism in children with chronic renal failure. Seventy four children with chronic renal insufficiency, 48 on conservative treatment (CRF) aged 13 +/- 3 years with creatinine clearance 45 +/- 21 ml/min/1.73m2 and 26 with end-stage renal disease (ESRD) aged 14 +/- 5 years were examined. The control group (K) consisted of 23 healthy children aged 10.8 +/- 3 years. In all children serum concentration of OPG, calcium (sCa), phosphorus (sP), PTH, CAP (cyclase activating PTH), CIP (cyclase inactive PTH) and osteocalcin (OC) were measured. OPG was determined by ELISA method (Biomedica), PTH and OC by IRMA (Duo-PTH, Scantibodies, USA and Osteo-Riact firm CIS, F).
Results: The concentration of OPG was higher in ESRD group (3 +/-1.6 pmol/l) than in K (1.95 +/- 0.56 pmol/l), p<0.005. The concentration of OPG in CRF group (2.42 +/- 1.4 pmol/l) was not different from this in K and ESRD. The concentration of OPG did not correlate with serum creatinine level. In CRF group no correlation was found between OPG level and the other parameters, in group ESRD the significant correlation between OPG and OC was found (R=0.55, p=0.006). The level of OPG in children CRF + ESRD correlated with PTH concentration (R=0.27, p<0.03), CAP (R=0.29, p<0.02), CIP (R=0.23, p<0.05) and OC (R=0.25, P<0.04). In patients with higher PTH level (> 200 pg/ml) the higher correlations between OPG and PTH, CAP and CIP were found. No significant correlation between PTH and OPG in patients with lower PTH level (< 200 pg/ ml) was found. No significant correlation between OPG and OC in patients with lower and higher PTH was found.
Conclusion: The elevated levels of OPG in children with ESRD may reflect the higher bone turnover in these patients.