The hypofunction of the parathyroid glands or the removable of the parathyroid glands (i.e., parathyroidectomy) in both man and animals causes tetany which is a hyperirritability of the nervous system and which may be characterized by twitching of the muscles and spasms of the body.
During this condition, the calcium ion level in the blood falls from 10 mg per 100 ml (normal) to 7 mg per 100 ml, convulsions occur if the level falls further.
As the calcium level decreases in the blood, there is a decrease in the urine. However, during this condition the phosphorus in the blood increases from a normal 5 mg per 100 ml to 9 mg per 100 ml and even higher.
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The hypofunction of the parathyroid glands can be checked by adjustment of the calcium and phosphate intake in the diet; that is, add 1% calcium gluconate or lactate to the diet and decrease the phosphate supply.
Hyperfunction of the parathyroid glands (hyperparathyroidism):
Hyperparathyroidism is a condition caused by over activity of the parathyroid glands.
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Hyperfunction of the parathyroid glands causes extensive decalcification and may lead to bony deformities and fractures.
Calcification of soft tissues, especially the kidneys, may occur. If calcium salts precipitate in the kidneys and ureters, kidney stones result and renal insufficiency develops.
Ultimobranchial bodies:
In fishes behind the last gill-pouches there occurs a pair of outpushings called ultimobranchial bodies. Because these bodies are associated with calcium metabolism in teleosts, they are regarded as the forerunners of, or as homologous with, the parathyroids.