Burosumab is a recombinant fully human monoclonal antibody (immunoglobulin G1) that directly binds to FGF23 and blocks the intracellular signaling caused by the FGF23/Klotho/FGF receptor 1 (FGFR1) complex.14 Burosumab neutralizes the action of FGF23 that causes hypophosphatemia in XLH and thereby normalizes P reabsorption in the kidney.15, 16 Furthermore, its intestinal absorption is associated with increased 1,25(OH)2D3 levels, which may improve chronic hypophosphatemia.15, 16. Here, FGF23 is linked to hypophosphatemia.