FGF23 and hypophosphatemia: FGF23 inhibits phosphate re-absorption by acting on the co-receptor FGFR1-Klotho and decreasing the expression and function of the sodium-dependent phosphate cotransporter in the renal proximal tubule (i.e., NAPT2a and NPT2c), so that an excess of FGF23 leads to hyperphosphaturia, phosphate wasting, and consequent hypophosphatemia [14].