A previous prospective study, including 3,879 CKD stage 2–4 patients, indicated that FGF-23 was positively correlated with pro-inflammatory cytokines such as IL-6, CRP, and TNF-α, but there was no experiment to confirm the causal relationship between FGF-23 and pro-inflammatory cytokines (Mendoza et al., 2012). Here, FGF23 is linked to chronic kidney disease.