Parathyroid hormone is secreted by the parathyroid glands which are paired endocrine glands (4 of them total) that sit on the back side of the thyroid gland. Parathyroid hormone is a polypeptide compound made up of 84 amino acids and acts to increase the concentration of calcium within the blood. It has a very short half-life (the amount of time it takes for 50% of the compound to degrade), approximately 4 minutes. Parathormone (parathyroid hormone) acts on 3 main tissues within the human body: bone (largest calcium resevoir within the body), the kidney, and the intestine. There is something called osteoclasts which break down bone and mobilize the calcium so that it can enter into the blood stream. PTH (parathyroid hormone) promotes the function of osteoclasts indirectly to help mobilize calcium. PTH also acts on something within the kidney called the distal tubules to promote calcium resorbtion, so that it is retained and not excreted in urine. Lastly, PTH increases calcium absorbtion within the intestine by increasing the amount of activated vitamin D which takes place in the kidney. I recommend discussing your own personal case with your primary care physician
in order to determine why your PTH levels are low. I hope this helps.