PTH and active vitamin D are well known as classical phosphate regulating hormones. However, presence of some phosphaturic factors is assumed from investigations about TIO, XLH, ADHR. Those diseases cause hypophsophatemia, hyperphosphaturia, low vitamin D and rickets/ostepmalacia. FGF-23, which has been detected from TIO tumors, can induce hypophosphatemia by direct inhibition on phosphate reabsorption and by suppressing 1,25 (OH)(2)D(3) production through the inhibition of 25-hydroxyvitaminD 1alpha-hydroxylase, in the kidney. We have still other phosphatonin candidates such as MEPE, FRP4, etc. The role of these substances are not clear yet. Future investigations are required to clarify their roles in phosphate metabolism.