There are four small parathyroid glands located just behind the thyroid gland—each only about the size of a grain of rice. Although similar in name, the parathyroid glands have nothing to do with the function of the thyroid. The role of each parathyroid gland is to constantly regulate the level of calcium in the blood, much like a thermostat regulates the heat inside a home. With hyperparathyroidism, one or more overactive parathyroid glands result in too much calcium in the blood, increasing the risk for bone fractures or kidney stones. Much less common is hypoparathyroidism, which is caused by one or more underactive parathyroid glands.
Your doctor can perform a simple blood calcium test to determine whether you have overactive or underactive parathyroid glands. Surgery is the most common treatment for hyperparathyroidism, and hypoparathyroidism is typically treated with a lifetime of supplements.