CASR and familial hypocalciuric hypercalcemia: FHH is a disorder of Ca2+e homeostasis characterized by lifelong elevations in serum calcium concentrations, normal or increased PTH, and inappropriately low urinary calcium excretion18 and is most frequently caused by loss-of-function CaSR mutations (FHH1) but can also be caused by Gα11 (FHH2) and AP2σ mutations.19