The parathyroids are four tiny glands in your neck, two on each side of your thyroid gland. They make parathyroid hormone (PTH) which controls the level of calcium in the blood. Calcium is very important for the normal functioning of muscles, nerves, and bones. It is absorbed through the intestines and stored in the bones. Parathyroid hormone raises blood levels of calcium by increasing intestinal absorption of calcium, and by dissolving calcium from the bone into the bloodstream.