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Parathyroid hormone (PTH) blood test

Parathormone; Parathormone (PTH) intact molecule; Intact PTH; Hyperparathyroidism - PTH blood test; Hypoparathyroidism - PTH blood test

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Definition

The PTH test measures the level of parathyroid hormone in the blood.

PTH stands for parathyroid hormone. It is a protein hormone released by the parathyroid gland.

A laboratory test can be done to measure the amount of PTH in your blood.

How the Test is Performed

A blood sample is needed.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.

How to Prepare for the Test

Ask your health care provider if you should stop eating or drinking for some period of time before the test. Most often, you will not need to fast or stop drinking.

Normal Results

Normal values are 10 to 55 picograms per milliliter (pg/mL).

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different specimens. Talk to your provider about the meaning of your specific test results.

Risks

There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

  • Excessive bleeding
  • Multiple punctures to locate veins
  • Fainting or feeling lightheaded
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)

What Abnormal Results Mean

A higher-than-normal level may occur with:

  • Disorders that increase phosphate or phosphorous levels in the blood, such as long-term (chronic) kidney disease
  • Failure of the body to respond to PTH (pseudohypoparathyroidism)
  • Lack of calcium, which may be due to not eating enough calcium, not absorbing calcium in the gut, or losing too much calcium in your urine
  • Pregnancy or breastfeeding (uncommon)
  • Swelling in the parathyroid glands, called primary hyperparathyroidism
  • Tumors in the parathyroid gland, called adenomas
  • Vitamin D disorders, including not enough sunlight in older adults and problems absorbing, breaking down, and using vitamin D in the body

A lower-than-normal level may occur with:

Other conditions for which the test may be ordered include:

Why the Test is Performed

PTH is released by the parathyroid glands. The 4 small parathyroid glands are located in the neck, near or attached to the back side of the thyroid gland. The thyroid gland is located in the neck, just above where your collarbones meet in the middle.

PTH controls calcium, phosphorus, and vitamin D levels in the blood. It is important for regulating bone growth. Your provider may order this test if:

To help understand whether your PTH is normal, your provider will measure your blood calcium at the same time.

Review Date: 11/17/2017
Reviewed By: Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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