Testosterone

A testosterone test checks the level of this male hormone (androgen) in the blood. Testosterone affects sexual features and development. In men, it is made in large amounts by the testicles. In both men and women, testosterone is made in small amounts by the adrenal glands; and, in women, by the ovaries.

The pituitary gland controls the level of testosterone in the body. When the testosterone level is low, the pituitary gland releases a hormone called luteinizing hormone (LH). This hormone tells the testicles to make more testosterone. See a picture of the pituitary gland.

Before puberty, the testosterone level in boys is normally low. Testosterone increases during puberty. This causes boys to develop a deeper voice, get bigger muscles, make sperm, and get facial and body hair. The level of testosterone is the highest around age 40, then gradually becomes less in older men.

In women, the ovaries account for half of the testosterone in the body. Women have a much smaller amount of testosterone in their bodies compared to men. But testosterone plays an important role throughout the body in both men and women. It affects the brain, bone and muscle mass, fat distribution, the vascular system, energy levels, genital tissues, and sexual functioning.

Most of the testosterone in the blood is bound to a protein called sex hormone binding globulin (SHBG). Testosterone that is not bound ("free") can also be checked if a man or a woman is having sexual problems.

A testosterone test is done to:

• See why a man is having problems in fathering a child (infertility). A low amount of testosterone can lead to low sperm counts.
• Check a man's sexual problems. A low level of testosterone may lower a man's sex drive or not allow him to have an erection (erectile dysfunction).
• See whether a high level of testosterone is causing a boy younger than age 10 to have early signs of puberty.
• Check a decreased sex drive in a woman. This may be due to the level of testosterone in her body.
• Find out why a woman is developing male features, such as excessive facial and body hair (hirsutism) and a deep voice.
• Find out why a woman is having irregular menstrual periods.
• See if testosterone-lowering medicines are working in a man with advanced prostate cancer.
• Find the cause of osteoporosis in a man.

You do not need to do anything before you have this test. Your doctor may want you to do a morning blood test, when testosterone levels are highest.

The health professional taking a sample of blood will:

• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
• Clean the needle site with alcohol.
• Put the needle into the vein. More than one needle stick may be needed.
• Attach a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Put a gauze pad or cotton ball over the needle site as the needle is removed.
• Pur pressure to the site and then a bandage.

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

There is very little chance of a problem from having blood sample taken from a vein.

• You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
• In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
• Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.

A testosterone test checks the level of this male hormone (androgen) in the blood.

Normal

Normal values may vary from lab to lab. Your doctor will have your test results in 1 to 2 days.

The testosterone level for a postmenopausal woman is about half the normal level for a healthy, nonpregnant woman. And a pregnant woman will have 3 to 4 times the amount of testosterone compared to a healthy, nonpregnant woman.

Normal free testosterone levels in men range from 44 to 244 pg/mL (0.68 to 3.76 pmol/L). In women, the free testosterone level may range from 0.6 to 9.2 pg/mL (0.01 to 0.14 pmol/L).

High values

• In men, a high level of testosterone may be caused by cancer of the testicles or adrenal glands.
• In boys younger than 10, a high level of testosterone may mean early (precocious) puberty, a tumor in the testicles, or an abnormal adrenal gland.
• In women, a high level of testosterone may be caused by cancer of the ovaries or adrenal glands or polycystic ovary syndrome (PCOS).

Low values

• In men or boys who have gone through puberty, a low level of testosterone may be caused by a problem with the testicles, such as slow development of, an injury to, or a lack of testicles. It can also be caused from treatment with the female hormone estrogen, a problem with the pituitary gland, or many long-term (chronic) illnesses.
• A low testosterone level in men can also be caused by certain inherited diseases (such as Klinefelter syndrome or Down syndrome), liver disease (cirrhosis), or treatment for cancer of the prostate gland.
• Chronic alcohol use can cause a low testosterone level.
• In women, a low level of testosterone may be caused by an underactive pituitary gland, Addison's disease, loss of ovary function through disease or surgery, and some medicines (such as corticosteroids or estrogen).

Reasons you may not be able to have the test or why the results may not be helpful include:

• Taking medicines such as estrogen (including birth control pills), testosterone, corticosteroids, digoxin (Lanoxin), spironolactone (Aldactone), or barbiturates.
• Having hyperthyroidism. This can raise sex hormone binding globulin (SHBG) levels. Hypothyroidism can lower SHBG levels.
• Taking medicines to treat prostate cancer.
• Taking medicines that raise prolactin levels, such as certain seizure medicines.

• Most of the testosterone in the blood is bound to a protein called sex hormone binding globulin (SHBG). "Free" testosterone may be checked when conditions that can increase SHBG levels, such as obesity or hyperthyroidism, are present.
• The levels of other hormones made by the pituitary gland, such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH), may be checked to see whether a low testosterone level is caused by problems with the testicles or ovaries or the pituitary gland. For more information, see the medical tests Luteinizing Hormone and Follicle-Stimulating Hormone. A really high level of LH and a low level of testosterone often means that the testicles or ovaries are not working properly. A low LH level and a really low or high testosterone level may mean a problem with the pituitary gland.
• For women, medicines such as birth control pills or corticosteroids may lower levels of testosterone. Oral estrogens used for hormone replacement therapy can also lower testosterone levels.

Other Works Consulted

• Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.

• Fischbach FT, Dunning MB III, eds. (2004). Manual of Laboratory and Diagnostic Tests, 7th ed. Philadelphia: Lippincott Williams and Wilkins.

• Pagana KD, Pagana TJ (2006). Mosby’s Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby.

• Shifren JL, et al. (2006). Testosterone patch for the treatment of hypoactive sexual desire disorder in naturally menopausal women: Results from the INTIMATE NM1 study. Menopause: The Journal of the North American Menopause Society, 13(5): 770–779. [Erratum in Menopause, 14(1): 157.]

• Somboonporn W, et al. (2007). Testosterone for peri- and postmenopausal women. Cochrane Database of Systematic Reviews (4).