The Calcium Sensing Receptor (CaSR) is a member of the G protein-coupled receptor (GPCR) family, primarily expressed in the parathyroid gland and kidneys, regulating the concentration of calcium ions (Ca2+) in the body. CaSR monitors changes in Ca2+ concentration in the blood, regulating the secretion of parathyroid hormone, thereby affecting calcium absorption, excretion, and skeletal storage to maintain calcium homeostasis. Gene mutations can lead to imbalances in calcium ion homeostasis, resulting in diseases such as familial hypocalciuric hypercalcemia and familial hypercalcemia. The activity of CaSR is modulated by various drugs used to treat diseases associated with calcium homeostasis imbalance.