The following findings support the rationale for suggesting renal outcome as the fourth outcome of CKD-MBD: (1) the observed association of FGF23 and vitamin D status with renal outcome [6]; (2) administration of native vitamin D and active vitamin D reduces albuminuria and proteinuria, respectively; (3) phosphate load exacerbates renal fibrosis in an animal study [50]; (4) VDR activators attenuate renal fibrosis in an animal model; and (5) high levels of serum phosphate or FGF23 attenuate the renoprotective effect of angiotensin receptor blockade [51]. The gene discussed is FGF23; the disease is renal fibrosis.