X-linked hypophosphatemia (XLH) is a rare bone disease characterized by high levels of FGF23, leading to hypophosphatemia and impaired production of the active form of vitamin D, 1,25 dihdroxyvitamin D (1,25D). Patients with XLH have short stature (rickets) and poorly mineralized bones. Their bones have poor quality, in part due to increased resorption of bone surrounding osteocytes and poor connectivity between cells.  As adults, they develop an abnormal hardening of the bone-tendon insertion site (enthesis), which causes significant pain and mobility issues. Our laboratory is interested the hormonal and molecular regulation of these complications.