<P> Parathyroid disease is conventionally divided into states where the parathyroid is overactive (hyperparathyroidism), and states where the parathyroid is under - or hypoactive (hypoparathyroidism). Both states are characterised by their symptoms, which relate to the excess or deficiency of parathyroid hormone in the blood . </P> <P> Hyperparathyroidism is the state in which there is excess parathyroid hormone circulating . This may cause bone pain and tenderness, due to increased bone resorption . Due to increased circulating calcium, there may be other symptoms associated with hypercalcemia, most commonly dehydration . Hyperparathyroidism is most commonly caused by a benign proliferation of chief cells in single gland, and rarely MEN syndrome . This is known as primary hyperparathyroidism, which is generally managed by surgical removal of the abnormal parathyroid gland . </P> <P> Renal disease may lead to hyperparathyroidism . When too much calcium is lost, there is a compensation by the parathyroid, and parathyroid hormone is released . The glands hypertrophy to synthesise more parathyroid hormone . This is known as secondary hyperparathyroidism . If this situation exists for a prolonged period of time, the parathyroid tissue may become unresponsive to the blood calcium levels, and begin to autonomously release parathyroid hormone . This is known as tertiary hyperparathyroidism . </P> <P> The state of decreased parathyroid activity is known as hypoparathyroidism . This is most commonly associated with damage to the glands or their blood supply during thyroid surgery--it may be associated with rarer genetic syndromes such as DiGeorge syndrome, which is inherited as an autosomal dominant syndrome . Hypoparathyroidism will occur after surgical removal of the parathyroid glands . </P>

Where is the parathyroid gland located and how does it function