How Does Parathyroid Hormone Increase Blood Calcium?
Like all endocrine glands, parathyroids make a hormone (a small protein capable of causing distant cells in the body to react in a specific manner). Parathyroid hormone (PTH) has a very powerful influence on the cells of the bones which causes them to release their calcium into the bloodstream. Calcium is the main structural component of bones which give them their rigidity. Under the presence of parathyroid hormone, bones will give up their calcium in an attempt to increase the blood level of calcium. Under normal conditions, this process is very highly tuned and the amount of calcium in our bones remains at a normal high level. Under the presence of too much parathyroid hormone, however, the bones will continue to release their calcium into the blood at a rate which is too high resulting in bones which have too little calcium. This condition is called osteopenia and osteoporosis and is illustrated in the bone segment on the top which has larger “pores” and less bone mass. When bones
