FGF23 and chronic obstructive pulmonary disease: There was the possibility that the change of phosphate metabolism has been related to hyperphosphatemia in this study, however, increases of blood parathyroid hormone and Fibroblast growth factor 23 level and decrease of blood 1,25(OH)2 D level, which have reported to be the factors related with poor prognosis in several illness such as COPD and sepsis [28–31], have normally caused hypophosphatemia rather than hyperphosphatemia.