Clinically, mutations in CASR can either cause hypercalcemia if the receptor is inactivated (loss-of-function), resulting in familial hypocalciuric hypercalcemia, or hypocalcemia if the receptor is activated (gain-of-function) to produce a hypersensitive receptor, causing autosomal-dominant hypocalcemia (ADH) (13). Here, CASR is linked to familial hypocalciuric hypercalcemia.