CaSR is a cation receptor through which extracellular calcium may influence cell activity, thus connecting the extracellular environment with the intracellular compartment. CaSR presence in parathyroid glands and kidney tubules has a specific relevance for calcium metabolism, because it ensures the strict control of the extracellular calcium concentration. Numerous findings have showed the relevance of CaSR for correct growth and healthy life, whereas genetic or acquired alterations of CaSR function may result in hypocalcemic or hypercalcemic disorders.