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parathyroid hormone

parathyroid hormone or parathormone, a hormone secreted by the parathyroid glands that regulates the metabolism of calcium and phosphate in the body. It has been purified extensively and appears to be a protein containing 84 amino-acid residues, a sequence of which about 33 to 35 are necessary for biological activity. Parathyroid hormone acts to raise the extracellular calcium concentration, that is, the concentration of calcium ions in the spaces between the cells of the body and in the blood plasma; it promotes the absorption of calcium by the intestine, mobilizes calcium salts from the bones, and increases the tendency of the kidney to recover calcium from the urine. The hormone also enhances both the excretion of phosphate by the kidneys and its uptake by the cells. This removes phosphate, which tends to form a relatively insoluble salt with calcium, from the extracellular spaces, allowing more calcium to remain in solution. Calcium is intimately involved not only in the formation of bone, but also in the functioning of the nervous system; thus hypoparathyroidism, the disease associated with a deficiency in parathyroid hormone secretion, is characterized by muscle spasms leading eventually to generalized convulsions and various psychiatric symptoms. This condition is sometimes successfully treated by the administration of the hormone. Hyperparathyroidism, the result of oversecretion of the hormone, often leads to the resorption of bone and can only be treated by the surgical removal of all of the parathyroid glands, which can be found in unusual locations.

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"parathyroid hormone." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 11 Dec. 2017 <http://www.encyclopedia.com>.

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"parathyroid hormone." The Columbia Encyclopedia, 6th ed.. . Retrieved December 11, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/parathyroid-hormone

parathyroid hormone

parathyroid hormone (PTH; parathormone; parathyrin) A peptide hormone secreted by the parathyroid gland in response to low levels of calcium in the blood. It acts to maintain normal blood levels of calcium by (1) increasing the number of osteoclasts, which break down the bone matrix and release calcium into the blood; (2) increasing the reabsorption of calcium and magnesium ions in the kidney tubules, so that their concentration is maintained in the blood; (3) converting vitamin D to its active form, which increases calcium absorption in the intestine. Parathyroid hormone acts in opposition to calcitonin.

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"parathyroid hormone." A Dictionary of Biology. . Encyclopedia.com. 11 Dec. 2017 <http://www.encyclopedia.com>.

"parathyroid hormone." A Dictionary of Biology. . Encyclopedia.com. (December 11, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/parathyroid-hormone-0

"parathyroid hormone." A Dictionary of Biology. . Retrieved December 11, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/parathyroid-hormone-0

parathyroid hormone

parathyroid hormone The hormone secreted by the parathyroid glands; four glands situated in the neck near to the thyroid gland but not connected with its function. The hormone is secreted in response to a fall in plasma calcium, and acts on the kidney to increase the formation of the active metabolite of vitamin D (calcitriol), leading to an increase in plasma calcium by increasing intestinal absorption and mobilizing the mineral from bones. It also reduces urinary excretion of phosphate.

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"parathyroid hormone." A Dictionary of Food and Nutrition. . Encyclopedia.com. 11 Dec. 2017 <http://www.encyclopedia.com>.

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parathyroid hormone

parathyroid hormone (parathormone) n. a hormone, synthesized and released by the parathyroid glands, that controls the distribution of calcium and phosphate in the body. A deficiency of the hormone lowers blood calcium levels, causing tetany. Compare calcitonin.

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"parathyroid hormone." A Dictionary of Nursing. . Encyclopedia.com. 11 Dec. 2017 <http://www.encyclopedia.com>.

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parathormone

parathormone Commonly used as an abbreviation for the parathyroid hormone; correctly a trade name for a pharmaceutical preparation of the hormone.

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"parathormone." A Dictionary of Food and Nutrition. . Encyclopedia.com. 11 Dec. 2017 <http://www.encyclopedia.com>.

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"parathormone." A Dictionary of Food and Nutrition. . Retrieved December 11, 2017 from Encyclopedia.com: http://www.encyclopedia.com/education/dictionaries-thesauruses-pictures-and-press-releases/parathormone

parathormone

parathormone (pa-ră-thor-mohn) n. see parathyroid hormone.

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"parathormone." A Dictionary of Nursing. . Encyclopedia.com. 11 Dec. 2017 <http://www.encyclopedia.com>.

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parathormone

parathormone: see parathyroid hormone.

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"parathormone." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 11 Dec. 2017 <http://www.encyclopedia.com>.

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"parathormone." The Columbia Encyclopedia, 6th ed.. . Retrieved December 11, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/parathormone

parathyroid hormone

parathyroid hormone See PARATHYROIDS.

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"parathyroid hormone." A Dictionary of Zoology. . Encyclopedia.com. 11 Dec. 2017 <http://www.encyclopedia.com>.

"parathyroid hormone." A Dictionary of Zoology. . Encyclopedia.com. (December 11, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/parathyroid-hormone

"parathyroid hormone." A Dictionary of Zoology. . Retrieved December 11, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/parathyroid-hormone