FGF23 and Hypercalcemia: In the present study, we aimed to understand whether the effect of Ca2+ regulating FGF23 levels was dependent on changes of the other two main hormones involved in its regulation, namely, PTH and vitamin D. The results show that, in a model of hypercalcemia with constant levels of PTH, FGF23 regulation by calcium is partly dependent on changes in vitamin D signaling.