Parathyroid Hormone
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Test Overview
A parathyroid hormone (PTH) blood test measures the level of parathyroid hormone in the blood. This test is used to help identify hyperparathyroidism or to find the cause of abnormal calcium levels. PTH controls calcium and phosphorus levels in the blood.
PTH is made by the parathyroid glands 
, which are four pea-sized glands that lie behind the thyroid gland. If the blood calcium level is too low, the parathyroid glands release more PTH. This causes the bones to release more calcium into the blood and reduces the amount of calcium released by the kidneys into the urine. Also, vitamin D is converted to a more active form, causing the intestines to absorb more calcium and phosphorus. If the calcium level is too high, the parathyroid glands release less PTH, and the whole process is reversed.
PTH levels that are too high or too low can cause problems with the kidneys and bones and cause changes in calcium and vitamin D levels.
Tests for calcium and phosphorus levels in the blood may be done at the same time as a PTH test.
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| Last updated: | June 11, 2008 |
|---|---|
| Author: | Bets Davis, MFA |
| Reviewed By: | Caroline S. Rhoads, MD - Internal Medicine, Matthew I. Kim, MD - Endocrinology & Metabolism |
| Editors: | Maria Essig, Tracy Landauer |
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