The parathyroid glands are four small oval bodies located on either side of, and on, the dorsal aspect of the thyroid gland. These glands control the level of calcium in the blood. Calcium is important, not only for bones and teeth, but also for nerve functioning, muscle contractions, blood clotting and glandular secretion. If we don’t have enough calcium for these functions, the body will take it from the bones, causing them to weaken and increasing the risk of fracture. Calcium deficiency may also cause twitching, spasms, convulsions and even death, while too much calcium can lead to a weakening of muscle tone and kidney stones.