While serum soluble α-Klotho concentrations are inversely correlated with serum FGF23 [46] and reductions in α-Klotho mRNA levels in the kidney have been observed with CKD and other states of FGF23 excess FGF23 [47], direct regulation of α-Klotho by FGF23 has not been previously demonstrated. Here, FGF23 is linked to chronic kidney disease.