Correlation of serum fibroblast growth factor-23 levels and calcium phosphate products levels in chronic kidney disease; sub analysis of chronic kidney disease-mineral and bone disorder study

Introduction: The body produces fibroblast growth factor-23 (FGF-23) to maintain normal phosphate levels when hyperphosphatemia occurs. Production of FGF-23 indirectly causes hypocalcemia. Phosphate and calcium disturbances also occur in chronic kidney disease (CKD), therefore this adaptation mechanism applies. This situation; however, only manifests in the early stages of CKD; if the estimated glomerular filtration rate (eGFR) is less than 30% of normal. This adaptation is no longer adequate and levels of calcium-phosphate (Ca×P) products and FGF-23 still rise. Objectives: In this study, the correlation between both the serum levels of FGF-23 and Ca×P products in CKD was analyzed. Patients and Methods: A cross-sectional study including 78 subjects with CKD stages 3 to 5 dialysis was conducted. Serum FGF-23 levels were determined using the enzyme-linked immunosorbent assay (ELISA) method and Ca×P product levels were calculated using the formula calcium (mg/ dL) × phosphate (mg/dL). The Kolmogorov-Smirnov test and Spearman’s test were conducted in the statistical study. If the P value is less than 0.05, the statistical findings are significant. Results: Serum FGF-23 levels and Ca×P product levels were shown to be significantly correlated. This analysis of the two correlations was independent of age and diabetes mellitus (DM). Based on stages of CKD, serum FGF-23 levels and Ca×P product levels were discovered to be significantly correlated only at stage 5 of non-dialysis. Conclusion: Increasing serum FGF-23 levels were correlated with increased Ca×P product levels, particularly in CKD stage 5 non-dialysis subjects. This correlation was independent of age and DM.