You have more calcium in your body than any other mineral. Calcium has many important jobs. The body stores more than 99 percent of its calcium in the bones and teeth to help make and keep them strong. The rest is throughout the body in blood, muscle and the fluid between cells. Your body needs calcium to help muscles and blood vessels contract and expand, to secrete hormones and enzymes and to send messages through the nervous system.
PTH stands for parathyroid hormone. It is a protein hormone released by the parathyroid gland. Parathyroid hormone controls calcium, phosphorus, and vitamin D levels in the blood and bone. Release of PTH is controlled by the level of calcium in the blood. Low blood calcium levels cause increased PTH to be released, while high blood calcium levels block PTH release.