Testosterone

The Test

How is it used? When is it ordered? What does the test result mean? Is there anything else I should know?

How is it used?

Testosterone testing is used to diagnose several conditions in men, women, girls, and boys. Examples of some of these conditions include:

Delayed or precocious (early) puberty in boys
Decreased sex drive in men and women
Erectile dysfunction in men
Infertility in men and women
Testicular tumors in men
Hypothalamus or pituitary disorders
Hirsutism and virilization in girls and women

Typically, a test for total testosterone is used for diagnosis. The total testosterone test measures testosterone that is bound to proteins in the blood (e.g., albumin and sex-hormone binding globulin [SHBG]) as well as testosterone that is not bound. However, a test for free or bioavailable testosterone may be used if, for example, the level of SHBG in the blood is abnormal.

When is it ordered?

In boys with delayed or slowly progressing puberty, the test is often ordered with the FSH and LH tests. Although there are differences from individual to individual as to when puberty begins, it is generally by the age of 10 years. Some symptoms of delayed puberty may include:

Delayed development of muscle mass
Lack of deepening of the voice or growth of body hair
Slow or delayed growth of testicles and penis

The test also can be ordered when a young boy seems to be undergoing a very early (precocious) puberty with obvious secondary sex characteristics. Causes of precocious puberty in boys, due to increased testosterone, include various tumors and congenital adrenal hyperplasia.

In men, the test may be ordered when infertility is suspected or when a man has a decreased sex drive or erectile dysfunction. Some other symptoms include lack of beard and body hair, decreased muscle mass, and development of breast tissue (gynecomastia). Low levels of total and bioavailable testosterone have also been associated with a greater presence of visceral fat (midriff or organ fat), insulin resistance, and increased risk of coronary artery disease.

In females, testosterone testing may be done when a woman has irregular or no menstrual periods (amenorrhea), is having difficulty getting pregnant, or appears to have masculine features, such as excessive facial and body hair, male pattern baldness, and/or a low voice. Testosterone levels can rise because of tumors that develop in either the ovary or adrenal glandor because of other conditions, such as polycystic ovarian syndrome (PCOS).

What does the test result mean?

Males: The normal range for testosterone levels in men is broad and varies by stage of maturity and age. It is normal for testosterone levels to slowly decline starting in the third decade of life. The rate may increase in men who are obese or chronically ill and with the use of certain medications.

A low testosterone level (hypogonadism) may be due to:

Hypothalamic or pituitary disease
Genetic diseases that can cause decreased testosterone production in young men (Klinefelter, Kallman, and Prader-Willi syndromes) or testicular failure and infertility (as in myotonic dystrophy, a form of muscular dystrophy)
Impaired testosterone production because of acquired damage to the testes, such as from alcoholism, physical injury, orviral diseases like mumps

Increased testosterone levels in males can indicate:

Testicular tumors
Adrenal tumors that are producing testosterone
Use of androgens (also called anabolic steroids)
Early puberty of unknown cause in boys
Hyperthyroidism
Congenital adrenal hyperplasia

Females: In women, testosterone levels are normally low. Increased testosterone levels can indicate:

PCOS
Ovarian or adrenal gland tumor
Congenital adrenocortical hyperplasia

Is there anything else I should know?

Alcoholism and liver disease in males can decrease testosterone levels. Drugs, including androgens and steroids, can also decrease testosterone levels.

Prostate cancer responds to androgens, so many men with advanced prostate cancer receive drugs that lower testosterone levels.

Drugs such as anticonvulsants, barbiturates, and clomiphene can cause testosterone levels to rise. Women taking estrogen therapy may have increased testosterone levels.