Tight regulation of serum concentrations of calcium and phosphate is indispensable for maintaining normal physiological condition. Imbalance of this regulation leads to pathophysiological disorders including heart disease, chronic kidney disease, and ectopic calcification. Formation and mineralization of bone and tooth are greatly influenced by calcium and phosphate metabolism since both organs are mainly consist of calcium-phosphate. Calcium and phosphate homeostasis is under hormonal control on its target organs such as kidney, bone and intestine. Calcium and phosphate are absorbed in intestine and reabsorbed and excreted in kidney. Bone store and release them in response to changing physiological demand by osteoblastic bone formation and osteoclastic bone resorption. Bone is also important as an endocrine organ that releases FGF23 from osteocytes, a novel hormone that targets the kidney to inhibit phosphate reabsorption and 1α, 25 (OH) (2)D(3) production.