Health Encyclopedia

PTH

Definition

PTH stands for parathyroid hormone. It is a protein hormone released by the parathyroid gland. PTH is the most important regulator of the body's calcium and phosphorus levels.

Release of PTH is controlled by the level of calcium in the blood. Low blood calcium levels cause increased PTH to be released, while high blood calcium levels inhibit PTH release.

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

Alternative Names

Parathormone; Parathormone (PTH) intact molecule; Parathyroid hormone

How the test is performed

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

How to prepare for the test

You should not eat or drink anything except water for 10 to 12 hours before the test.

How the test will feel

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

Your doctor may order this test if you have abnormal calcium or phosphorus levels and a PTH abnormality is suspected.

Normal Values

Normal values are 10-55 picograms per milliliter (pg/mL). Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean

Greater-than-normal levels may be associated with:

Chronic kidney failure
Hyperparathyroidism
Increased blood lipids
Malabsorption syndrome
Osteomalacia in adults
Pregnancy or breastfeeding
Rickets in children
Use of certain medications such as rifampin, anticonvulsants, diuretics, lithium, and those containing phosphate
Vitamin D deficiency

Lower-than-normal levels may be associated with:

Accidental removal of parathyroid glands during neck surgery
Autoimmune destruction of parathyroid gland
Hypomagnesemia
Hypoparathyroidism
Metastatic bone tumor
Milk-alkali syndrome (excessive calcium ingestion)
Sarcoidosis
Vitamin D intoxication

Additional conditions under which the test may be performed:

What the risks are

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

References

Bilezikian JP, Potts JT, Fuleihan Gel-H, et al. Summary statement from a workshop on asymptomatic primary hyperparathyroidism: a perspective for the 21st century. J Bone Miner Res. 2002:17(Suppl2):N2-N11.

Review Date:10/24/2007
Reviewed By:Robert Hurd, MD, Professor of Endocrinology, Department of Biology, Xavier University, Cincinnati, OH, and physician in the Primary Care Clinic, Cincinnati Veterans Administration Medical Center, Cincinnati, Ohio. Review provided by VeriMed Healthcare Network.

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