FGF23 and craniosynostosis: Furthermore, although treating XLH with the conventional therapy of active vitamin D analogues (eg, calcitriol, alphacalcidol) and phosphate supplements may improve serum phosphate levels enough to ameliorate rickets in children, this does not appear to be able to prevent craniosynostosis,(20, 24, 25) and there is a lack of evidence on the effect of burosumab, a fully humanized immunoglobulin G antibody to FGF23, on the development of craniosynostosis.