Parathyroid Hormone (PTH) Test

Why It Is Done

A test for parathyroid hormone (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 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, which can by caused by neck surgery or radiation treatments.
• A rare disease, such as sarcoidosis or histiocytosis X.
• An overdose of vitamin D or calcium.
• Cancer, such as lymphoma or multiple myeloma.
• A low magnesium level.