The body needs precise regulation of minerals such as phosphorus. Many of the organs work together to regulate these levels. The intestines absorb minerals, while the kidneys intestines can excrete them, and certain organs can store and release them. Many mechanisms influence the absorption, excretion and storage of minerals. The parathyroid gland releases parathyroid hormone to regulate phosphorus.
Function
Parathyroid hormone regulates blood levels of calcium and phosphate. It increases calcium by releasing the mineral from bone, increases absorption from the kidneys so that less is excreted in the urine, and increases absorption from food in the intestines by increasing vitamin D synthesis in the kidneys. Parathyroid hormone decreases phosphate levels by increasing its secretion from the kidneys. It also increases absorption of phosphate from the bones and intestine, but the excretion from the kidneys out-paces absorption, so that the net effect of parathyroid hormone is to increase calcium and decrease phosphate. Phosphate primarily functions as an energy carrier and messenger in cells.
Regulation
Phosphate levels are regulated by parathyroid hormone. Parathyroid hormone is regulated by factors that increase or decrease its concentration in the blood. The hormone is increased by decreased calcium or increased phosphate. In contrast, it is decreased by increased levels of calcium or decreased phosphate. Changes in magnesium can effect parathyroid hormone levels as well, with small decreases in magnesium increasing levels and large drops in magnesium suppressing levels of the hormone.
Diseases
High parathyroid hormone is called hyperparathyroidism. Primary hyperparathyroidism is caused by problems in the parathyroid gland, such as excess tissue growth, causing the parathyroid to release excessive amounts of hormones. Secondary hyperparathyroidism is caused by low calcium from another disease stimulating the release of parathyroid hormone. If secondary hyperparathyroidism continues unchecked it can produce tertiary hyperparathyroidism. In this disorder, the parathyroid glands continue to release parathyroid hormone even if the calcium levels are corrected. High parathyroid hormone damages the bone and upsets the levels of phosphate and calcium in the bone. Hypoparathyroidism is caused by damage to or removal of the parathyroid gland, and results in decreased calcium and increased phosphorus in the blood.
Treatment
The treatment of hyperparathyroidism is generally removal of part of the parathyroid gland. The treatment of hypoparathyroidism is vitamin D, calcium, and a drug such as teriparatide, which mimics the effects of parathyroid hormone.
References
- "Physiology"; Linda S.Costanzo; 4th Ed 2008
- "Harrison's Principles of Internal Medicine"; Anthony S Fauci et al.; 17th Ed 2008
