Hyperparathyroidism is a disorder in which too much parathyroid hormone (PTH) is secreted from the parathyroid glands, resulting in abnormally high levels of calcium in the blood (hypercalcemia). Hyperparathyroidism is further classified as being primary, secondary, and tertiary.
Primary hyperparathyroidism is more common than either secondary or tertiary hyperparathyroidism, which occurs in patients with kidney failure or a severe vitamin D deficient state. The parathyroid glands are four pea-sized glands located next to the thyroid gland in the neck; they secrete PTH, which regulates the level of calcium in the blood.





