Definition

The parathyroid hormone-related protein (PTH-rP) test measures the level of a hormone in the blood, called parathyroid hormone-related protein.

Alternative Names

PTHrp; PTH-related peptide

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

No special preparation is necessary.

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 sensation. Afterward, there may be some throbbing or slight bruising. This soon goes away.

Why the Test is Performed

This test is done to find out whether a high blood calcium level is caused by an increase in PTH-related protein.

Normal Results

No detectable (or minimal) PTH-like protein is normal.

Women who are breastfeeding may have detectable PTH-related protein values.

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

What Abnormal Results Mean

An increased level of PTH-related protein with a high blood calcium level is usually caused by cancer.

PTH-related protein can be produced by many different kinds of cancers, including those of the lung, breast, head, neck, bladder, and ovaries. In about two thirds of people with cancer who have a high calcium level, a high level of PTH-related protein is the cause. This condition is called humoral hypercalcemia of malignancy (HHM) or paraneoplastic hypercalcemia.

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

References

Bringhurst FR, Demay MB, Kronenberg HM. Hormones and disorders of mineral metabolism. In: Melmed S, Auchus, RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 29.

Thakker RV. The parathyroid glands, hypercalcemia and hypocalcemia. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 227.