The Fam20c-cKO mice displayed a decreased level of renal 1α-hydroxylase in the presence of hypophosphatemia, indicating that in these mutant mice, the negative modulation of FGF23 on the expression of the 1α-hydroxylase may outweigh the stimulating effect of hypophosphatemia on the 1α-hydroxylase expression. This evidence concerns the gene FGF23 and hypophosphatemia.