Downregulation of osteoblast Phex expression by PTH.

Human/murine X-linked hypophosphatemia is a dominant disorder associated with renal phosphate wasting and defective bone mineralization. This disorder results from mutations in the PHEX/Phex (Phosphate-regulating gene with homologies to endopeptidases on the X chromosome) gene, which is expressed in fully differentiated osteoblasts. The purpose of the present study was to assess whether PTH, a major regulator of bone development and turnover, modulates osteoblastic Phex expression.