FGF23 and hypophosphatemia: Since FGF23 has dose-dependent effects on the kidney [69], [70], the 3-fold reduction in circulating FGF23 in Hyp;Fgfr1Dmp1-cKO-null mice likely accounts for the improvement in the hypophosphatemic rickets phenotype, whereas the persistent elevations of FGF23 would explain the residual hypophosphatemia and bone abnormalities in Hyp;Fgfr1Dmp1-cKO-null mice.