FGF23 and X-linked hypophosphatemic rickets: HR can be mainly divided into three types, including X-linked hypophosphatemic rickets (XLHR) due to a loss function of phosphate regulating gene with homologies to endopeptidases on the X chromosome (PHEX) [4], autosomal dominant hypophosphatemic rickets (ADHR) caused by mutation in the fibroblast growth factor 23 (FGF23) gene [5] and autosomal recessive hypophosphatemic rickets (ARHR) as a result of mutation in dentin matrix protein 1 (DMP1) gene, ecto-nucleotide pyrophos- phatase/phosphodiesterase 1 (ENNP1) gene, or family with sequence similarity 20, member C (FAM20C) [6–8].