In contrast, no effect of PTH (1–34) injection on serum phosphate levels was noted in NaPi2a−/− mice emphasizing that Napi2a is the dominant sodium phosphate co-transporter in the renal proximal tubule cells and responsible for the severe hyperphosphatemia in Fgf-23−/− mice. This evidence concerns the gene SLC34A1 and hyperphosphatemia.