Fibroblast growth factor 23 (FGF-23) is a primary regulator of renal phosphate excretion. FGF23 is inversely associated with the GFR, a relationship underlying a fundamental mechanism for maintaining serum phosphate constancy during CKD progression. Such an adaptation may have deleterious trade-offs because, independently of serum phosphate, high FGF23 signals a high risk of death in ESRD patients. Some studies showed that there is a relationship between FGF-23 levels and proteinuria in CKD patients.