At a Glance
Why Get Tested?
To detect an abnormal testosterone level in males and females; in males, to help diagnose the cause of erectile dysfunction, the inability of your partner to get pregnant (infertility), or premature or delayed puberty; in females, to help diagnose the cause of masculine physical features (virilization), infertility, or polycystic ovary syndrome (PCOS)
When to Get Tested?
For males, when you may be infertile or are unable to get or maintain an erection; when you are a boy with either early or delayed sexual maturity (puberty)
For females, when you have male traits, such as a low voice or excessive body hair (hirsutism), when you have abnormal uterine bleeding, do not menstruate (amenorrhea), or are infertile
Sample Required?
A blood sample drawn from a vein in your arm
Test Preparation Needed?
None
The Test Sample
What is being tested?
Testosterone is a steroid hormone (androgen) produced by special endocrine tissue (the Leydig cells) in the male testicles. It is also produced by the adrenal glands in both males and females and, in small amounts, by the ovaries in females. This test measures the level of testosterone in the blood.
In males, testosterone stimulates development of secondary sex characteristics, including enlargement of the penis, growth of body hair, muscle development, and a deepening voice. It is present in large amounts in males during puberty and in adult males to regulate the sex drive and maintain muscle mass. In women, testosterone is converted to estradiol, the main sex hormone in females.
Testosterone production is stimulated and controlled by luteinizing hormone (LH), which is manufactured by the pituitary gland. Testosterone works within a negative feedback mechanism: as testosterone increases, LH decreases, whereas increased LH causes decreased testosterone. Testosterone levels are diurnal, peaking in the early morning hours (about 4:00 to 8:00 am), with the lowest levels in the evening (about 4:00 to 8:00 pm). Levels also increase after exercise and also decrease with age. About two-thirds of testosterone circulates in the blood bound to sex-hormone binding globulin (SHBG) and slightly less than one-third bound to albumin. A small percent (about 1-4%) circulates as free testosterone.
In many cases, measurement of total testosterone provides the doctor with adequate information. However, in certain cases, for example when the level of SHBG is abnormal, a test for free or bioavailable testosterone may be performed as it may more accurately reflect the presence of a medical condition.
How is the sample collected for testing?
A blood sample is taken by needle from a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
The Test
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 gland or 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, or viral 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.
Common Questions
Ask a Laboratory Scientist
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Related Pages
On This Site
Conditions: Infertility, PCOS, Endocrine Syndromes, Testicular Cancer, Adrenal Insufficiency
Elsewhere On The Web
The Hormone Foundation: Low Testosterone and Men's HealthArticle Sources
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
(June 7, 2012) Kaplowitz. Precocious Puberty. Medscape Reference article. Available online at http://emedicine.medscape.com/article/924002-overview through http://emedicine.medscape.com. Accessed November 2012.
(June 6, 2012) Kemp S. Hypogonadism. Medscape Reference. Available online at http://emedicine.medscape.com/article/922038-overview through http://emedicine.medscape.com. Accessed November 2012.
(October 30, 2012) Lucidi R. Polycystic Ovarian Syndrome. Medscape Reference. Available online at http://emedicine.medscape.com/article/256806-overview through http://emedicine.medscape.com. Accessed November 2012.
The Endocrine Society's Clinical Guidelines. Testosterone Therapy in Adult Men with Androgen Deficiency Syndromes. J Clin Endocrinol Metab June 2010, 95(6):2536–2559. PDF available for download at http://www.endo-society.org/guidelines/final/upload/FINAL-Androgens-in-Men-Standalone.pdf through http://www.endo-society.org. Accessed November 2012.
Harrison's Principles of Internal Medicine, 18ed, Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson JL, Loscalzo J, Eds., McGraw-Hill. (2012) Chapters 49 & 346.
Sources Used in Previous Reviews
Clinical Chemistry: Theory, Analysis, Correlation. 3rd Edition. Lawrence A. Kaplan and Amadeo J. Pesce, St. Louis, MO. Mosby, 1996.
Clinical Chemistry: Principles, Procedures, Correlations. Michael L. Bishop, Janet L. Duben-Engelkirk, Edward P. Fody. Lipincott Williams & Wilkins, 4th Edition.
The Gale Encyclopedia of Childhood and Adolescence: Testosterone. Available online at http://www.findarticles.com/p/articles/mi_g2602 through http://www.findarticles.com.
Laurence M. Demers, PhD. Distinguished Professor of Pathology and Medicine, The Pennsylvania State University College of Medicine, The M. S. Hershey Medical Center, Hershey, PA.
Pagana K, Pagana T. Mosby's Manual of Diagnostic and Laboratory Tests. 3rd Edition, St. Louis: Mosby Elsevier; 2006, Pp 481-484.
(January 2006) The Hormone Foundation. Low Testosterone and Men's Health. PDF available for download at http://www.hormone.org/Resources/Reproduction/upload/bilingual_Testosterone.pdf through http://www.hormone.org. Accessed January 2009.
(January 2008) Eugster E, Palmert M, eds. The Hormone Foundation. Precocious Puberty. PDF available for download at http://www.hormone.org/Resources/Growth/upload/bilingual_precocious_puberty.pdf through http://www.hormone.org. Accessed January 2009.
Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER, Bruns DE, eds. St. Louis: Elsevier Saunders; 2006.
(March 18, 2008) Holt E. MedlinePlus Medical Encyclopedia. Testosterone. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003707.htm. Accessed January 2009.
(December 9, 2008) Mayo Clinic. Male hypogonadism. Available online at http://www.mayoclinic.com/health/male-hypogonadism/DS00300 through http://www.mayoclinic.com. Accessed January 2009.
