PHEX and hypophosphatemia: In addition to FGF23, several other molecules responsible for phosphate homeostasis are highly expressed in osteocytes, which include phosphate-regulating gene homologous to endopeptidase on X chromosome (PHEX), dentin matrix protein 1 (DMP1), and family with sequence similarity 20, member C (FAM20C), the genes responsible for hereditary hypophosphatemia (8–12).