The importance of the CaSR for the regulation of Ca2+e has been highlighted by the identification of >230 different germline loss- and gain-of-function CaSR mutations that give rise to disorders of Ca2+e homeostasis known as familial hypocalciuric hypercalcaemia type 1 (FHH1) and autosomal dominant hypocalcaemia type 1 (ADH1), respectively (11). The gene discussed is CASR; the disease is familial hypocalciuric hypercalcemia 1.