CASR and Familial hypocalciuric hypercalcemia type 1: ,4 The importance of CaSR-mediated signaling for Ca2+ homeostasis is confirmed by germline loss-of-function mutations in CASR (MIM: 145980; 239200), GNA11 (MIM: 145981), and AP2S1 (MIM: 600740) that cause familial hypocalciuric hypercalcemia types 1–3 (FHH1-3), respectively.