FGF23 and X-linked hypophosphatemia: Burosumab, first approved as a treatment for XLH in 2018 in the United States and for children in Europe, then as of 2020 also for the treatment of adults with XLH in Europe, is a fully human, immunoglobulin G1 monoclonal antibody that binds to and inhibits excess FGF23 activity, enabling restoration of serum phosphate levels (30–32).