There are four parathyroid glands. Except in rare instances, parathyroid glands are located in the neck, behind the thyroid. Parathyroid glands are not related to the thyroid, although they are located nearby in the neck. The parathyroid glands control the amount of calcium in your blood and the amount of calcium in your bones. Calcium provides electrical energy to our nervous and muscular systems, and provides strength to our skeletal system.
Over-activity of parathyroid hormone production can cause potentially high levels of calcium in the blood, leading to serious calcium imbalance. This condition is called hyperparathyroidism.
The four parathyroid glands are normally the size of a grain of rice. If you have parathyroid disease, you very likely have three normal parathyroid glands and one parathyroid tumor that is the size of an olive or grape (or even larger). A bad parathyroid gland leads to hyperparathyroidism, eventually causing you to develop osteoporosis unless the bad gland is removed. Hyperparathyroidism requires an operation to remove the one parathyroid gland which has become a tumor.