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Parathyroid Hormone (PTH) Test
Test Overview
A parathyroid hormone (PTH) blood test measures the level of parathyroid hormone, Opens dialog in the blood. This test is used to help identify hyperparathyroidism, Opens dialog, to find the cause of abnormal calcium, Opens dialog levels, or to check the status of chronic kidney disease. PTH controls calcium and phosphorus, Opens dialog levels in the blood.
PTH is made by the parathyroid glands, Opens dialog, which are four pea-sized glands that lie behind the thyroid gland, Opens dialog. 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, Opens dialog 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.
Why It Is Done
A test for parathyroid hormone, Opens dialog (PTH) is done to:
- Help identify hyperparathyroidism.
- Find the cause of an abnormal blood calcium level.
- Check to see whether a problem with the parathyroid glands, Opens dialog is causing the abnormal calcium level.
- Watch for problems in people who have chronic kidney disease.
How To Prepare
In general, there's nothing you have to do before this test, unless your doctor tells you to.
How It Is Done
A health professional uses a needle to take a blood sample, usually from the arm.
How It Feels
When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.
Risks
There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.
Results
Results are usually available in 1 to 2 days.
Normal
Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.
High values
High PTH levels may be caused by:
- A parathyroid gland growth (hyperplasia) or a parathyroid tumor.
- A low level of calcium in the blood. A low blood calcium level can be caused by kidney disease, kidney failure, severe vitamin D deficiency, or an inability of the intestines to absorb calcium from food.
- Some types of cancer, such as lung, kidney, pancreatic, or ovarian cancer.
Low values
Low PTH levels may be caused by:
- Damage to the parathyroid gland, Opens dialog, which can by caused by neck surgery or radiation treatments.
- A rare disease, such as sarcoidosis, Opens dialog or histiocytosis X.
- An overdose of vitamin D or calcium.
- Cancer, such as lymphoma, Opens dialog or multiple myeloma, Opens dialog.
- A low magnesium level.
Related Information
Credits
Current as of: April 30, 2024
Author: Ignite Healthwise, LLC Staff
Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.
Current as of: April 30, 2024
Author: Ignite Healthwise, LLC Staff
Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.
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