FGF23 and chronic kidney disease: When fed with an adenine diet to induce CKD, IL-6 knock-out mice failed to increase bone Fgf23 mRNA, resulting in an attenuation of circulating FGF23 levels in comparison to wild-type mice with CKD; these data suggest a direct contribution of IL-6 to the increased FGF23 observed during CKD (59).