Fibroblast growth factor-23 and early decrements in kidney function: the Heart and Soul Study

Methods. In 792 outpatients with stable cardiovascular disease (CVD) and normal kidney function to moderate CKD, we evaluate the associations of estimated glomerular filtration rate (eGFR) and albumin-to-creatinine ratio (ACR) with plasma FGF-23 concentrations. Results. Compared to participants with eGFR >= 90 ml/min/1.73m(2), mean FGF-23 concentrations were 7.8 RU/ml higher (4.3-11.5, P = 0.01) in those with eGFR 60-89 ml/min/1.73m(2) in models adjusted for age, sex, race, ACR, blood pressure, diabetes and body mass index. More advanced decrements in eGFR were associated with much higher FGF-23 concentrations. In spline analysis, the slope of change in FGF-23 concentration was evident at eGFR < 90 ml/min/1.73m(2). Compared to participants with ACR < 30 mg/g, mean FGF-23 concentrations were 18.4 RU/ml higher (9.3-29.2, P < 0.001) in those with ACR 30-299 mg/g in models adjusted for identical covariates plus eGFR and much higher in individuals with ACR >= 300 mg/g. Spline analysis demonstrated a linear relationship of ACR with FGF-23, independent of eGFR, even among persons with ACR < 30 mg/g. Conclusion. Modest decrements in eGFR or elevations in albuminuria are each independently associated with higher FGF-23 concentrations in outpatients with stable CVD.