Thus, TCAL and Galnt3-deficient mice are characterized by the presence of hyperphosphataemia, decreased plasma alkaline phosphatase activity, reduced circulating intact Fgf23, increased Fgf23 gene expression in bone, increased whole body BMD in male mice, and male infertility due to loss of spermatozoa in seminiferous tubules. This evidence concerns the gene FGF23 and hyperphosphatemia.