FGF23 and chronic kidney disease: Elevated FGF23 and decreased circulating αKlotho are observed in both aging and in CKD,116, 197, 198 leading to speculation that both CKD and the age‐related decline in this and other physiological functions are caused in part by increased FGF23 and decreased αKlotho.55 If true, this would assume soluble αKlotho acts as an inhibitor of αKlotho‐independent actions of FGF23.