You have four parathyroid glands that are each about the size of a pea. They are in your neck in back of your thyroid gland. These small glands make parathyroid hormones, or PTH, which helps control the level of calcium in your bones and blood. PTH also helps control vitamin D and phosphorus. These vitamins and minerals are needed to keep your bones and teeth strong. They also help your muscles and nerves work the right way. When your parathyroid glands release too much PTH, it is called hyperparathyroidism. This illness causes the calcium levels in your blood to become high. This can lead to high blood pressure and kidney stones. Doctors can treat hyperparathyroidism by treating the hidden health problems which cause the illness, or with surgery.