parathyroid hormone (PTH)
An 84-amino acid peptide hormone secreted
by the parathyroid gland in response
to low levels of calcium in the blood. Parathyroid hormone (PTH) acts to
maintain normal levels of blood calcium by:
- increasing the number of osteoclasts, cells that break down the bone
matrix and release calcium into the blood
- increasing the reabsorption of calcium and magnesium ions in the kidney
tubules, so that their concentration is maintained in the blood
- 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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BIOCHEMISTRY
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