The parathyroid glands are four pea sized glands located on the thyroid gland in the neck. Although their names are similar, the thyroid and parathyroid glands are entirely different glands, each producing distinct hormones with specific functions. The parathyroid glands secrete parathyroid hormone (PTH), a polypeptide that helps maintain the correct balance of calcium and phosphorous in the body. Hyperparathyroidism is increased secretion of parathyroid hormone from the parathyroid glands. Abnormally increased activity of the parathyroid glands, which may be primary or secondary. Excessive secretion of parathyroid hormone resulting in abnormally high levels of calcium in the blood can affect many systems of the body especially causing bone resorption and osteoporosis.