In summary (Table 2), CaR−/− mice had a very short lifespan, decreased body weight and displayed hypercalcemia, hypophosphatemia, elevated serum ALP, PTH and 1,25(OH)2D3; CaR−/−1α(OH)ase−/− mice had slightly increased lifespan and body weight and displayed normocalcemia, hypophosphatemia, greater elevations in PTH and ALP, and undetectable serum 1,25(OH)2D3; CaR−/−PTH−/− mice displayed normocalcemia, hyperphosphatemia, normal ALP levels, undetectable serum PTH and lower serum 1,25(OH)2D3. Here, PTH is linked to hypophosphatemia.