FGF23 and calcium metabolic disease: To our knowledge, in addition to vascular calcification, bone abnormality as another important characteristic of CKD–MBD includes calcium-phosphorus metabolic disorder and osteoporosis-like pathological lesions, which are involved in the unbalance of urine Ca2+ and P4+, serum Ca2+, P4+, ALP, FGF23, VD3 and iPTH, as well as BMD (Tamagaki et al., 2006).