17-OH progesterone is a blood test that measures the amount of 17-OH progesterone.

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. 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: The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any bleeding.

After the blood has been drawn, it is sent to a laboratory to be evaluated.

The health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test. These include corticosteroids and birth control pills. The health care provider may advise that the test be performed at a specific time of day, because this can affect the test results.

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

This test is used primarily to identify patients with congenital adrenal hyperplasia (CAH). CAH is a rare genetic disorder that results from a deficiency of a particular enzyme that normally makes cortisol in the adrenal gland. This deficiency results in abnormal levels of certain steroids and hormones, specifically increasing androgens (male hormones) and decreasing glucocorticoids.

• Cord blood - 1,000 - 3,000 ng/dL
• >24 hours - less than 100 ng/dL
• Adults - less than 200 ng/dL

Note: ng/dL = nanograms per deciliter. Normal and abnormal values differ for babies born with low birth weight.

Elevated levels of 17-OH progesterone are seen in congenital adrenal hyperplasia (CAH), or with some adrenal tumors. In infants affected by CAH, 17-OHP ranges from 3,000 - 40,000 ng/dL. In adults, a level >800 is very closely related to diagnosis of the CAH.

• 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

Your doctor may suggest an ACTH test if your level is greater than 200 ng/dL but less than 800 ng/dL.

This test is sensitive to circadian rhythms (the natural highs-and-lows that the body experiences during a day).

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Reference: Speroff L, Fritz MA, eds. Normal and Abnormal Sexual Development in Clinical Gynecologic Endocrinology & Infertility. Baltimore, Md: Williams & Wilkins; 2005.