Which of the following hormones is responsible for the breakdown of mineralised matrix of the bone to release calcium into the blood stream?

PTH raises the level of blood Ca2+ through direct effects in bones and the kidneys and an indirect effect on the intestine. PTH activates the osteoclasts in bones. It in turn causes the mineralised matrix to break down, releasing Ca2+ into the blood. In the kidneys, PTH directly stimulates reabsorption of Ca2+ through the renal tubules. In addition, PTH indirectly raises blood Ca2+ levels by promoting production of vitamin D.