FGF23 and X-linked hypophosphatemia: On the contrary, in a mouse model of X-linked hypophosphatemia, Xiao et al. [45] found that the conditional deletion of Fgfr-1 in osteocytes contributed to a 30% reduction in bone FGF-23 expression and a 70% reduction in serum FGF-23 concentration as well as a significant improvement in rickets and osteomalacia.