Serum fibroblast growth factor 23 and calcium-phosphorus metabolism parameters in children with chronic kidney disease - preliminary report.

INTRODUCTION: In chronic kidney disease (CKD) the function of all factors regulating mineral metabolism is disturbed, leading inevitably to renal osteodystrophy and vascular calcification. The aimof the study is to assess concentrations of fibroblast growth factor 23 (FGF 23), osteoprotegerin (OPG) and other parameters of calcium-phosphate metabolism in children with CKD.

MATERIAL AND METHODS: 37 children with CKD 3-5, aged 1.6-17 years were included in the study. In all children serum levels of calcium (sCa), phosphate (sP), creatinine, alkaline phosphatase (ALP), FGF 23, intact parathormone (PTH), OPG and receptor activator nuclear factor κB ligand (RANKL) were measured.

RESULTS: Total calcium concentration was within normal limits in all children included in this study. Hyperphosphatemia was found in 2 children from group CKD 3 (12%), 6 from CKD 4 (54%) and 1 from CKD 5 (11%). FGF 23 level increased consecutively in subsequent CKD stages achieving the highest values in CKD 5 group. In all children with CKD, serum levels of OPG were correlated with FGF 23. In children with CKD 3-4 negative correlation between FGF 23 and PTH (r=-0.45; p=0.02) and positive correlation between FGF 23 and RANKL (r=0,59; p=0.006) has been found. Positive correlation between OPG concentration and HCO3 -and BE levels has been observed, as well as negative correlation between RANKL/OPG ratio and HCO3 -and BE levels.

CONCLUSION: Despite maintaining serum calcium, phosphorus and PTH levels within recommended limits, elevated levels of FGF 23 and OPG were observed in children with chronic kidney disease, especially in it's end-stage.