DefinitionHyperparathyroidism is excessive production of parathyroid hormone (PTH) by the parathyroid glands.See also:Primary hyperparathyroidismSecondary hyperparathyroidismCauses, incidence, and risk factorsThe parathyroid glands are located in the neck, near or attached to the back side of the thyroid gland. They produce parathyroid hormone, which controls calcium, phosphorus, and vitamin D levels within the blood and bone.When calcium levels are too low, the body responds by increasing production of parathyroid hormone. This increase in parathyroid hormone causes more calcium to be taken from the bone and more calcium to be reabsorbed by the intestines and kidney. When the calcium level returns to normal, parathyroid hormone production slows down.There are two main types of hyperparath