As previously discussed, the gain-of-function CaSR mutations result in autosomal dominant hypocalcemia (ADH) or type 5 Bartter syndrome and eight of them are clustered in loop 2 close to the two cysteines responsible for receptor homodimerization, i.e. cys 129 and cys 131 [34]. The gene discussed is CASR; the disease is autosomal dominant hypocalcemia.