What are the parathyroid glands ?
The parathyroid glands are very small. There are 4 of them and they sit behind the thyroid gland in the lower part of the neck.
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The parathyroid glands can be seen here once the thyroid gland has been lifted forwards. The blood supply to the thyroid is shown. The relationship of the parathyroid glands to the arteries is seen. ITA = inferior thyroid artery STA = superior thyroid artery
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They produce parathormone which acts to maintain body calcium levels (by taking calcium out of bones and increasing calcium absorption from the gut). Parathormone also acts on the kidney where activation of vitamin D occurs. Vitamin D is also involved in increasing body calcium levels.
Parathormone levels are controlled by the levels of calcium in the blood. Low calcium levels stimulate the production of the hormone.