To detect an abnormal testosterone level in males and females:
To monitor testosterone levels in transgender individuals who are undergoing hormone therapy
A blood sample drawn from a vein
None, but the sample is typically collected in the morning.
Testosterone is the main sex hormone (androgen) in men. Although it is considered a "male" sex hormone, it is present in the blood of both men and women. However, testosterone levels are normally much higher in men than in women. This test measures the level of testosterone in your blood. It is measured as total testosterone, either alone or in combination with free testosterone and/or bioavailable testosterone.
Testosterone is mainly produced by 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.
Testosterone production is stimulated and controlled by luteinizing hormone (LH), which is made by the pituitary gland. Testosterone works within a negative feedback loop:
Testosterone levels are diurnal, with the highest (peak) levels occurring in the early morning hours (about 4:00 to 8:00 am) and the lowest levels occurring in the evening (about 4:00 to 8:00 pm). Levels also increase after exercise and decrease with age.
About two-thirds of testosterone circulates in your blood bound to the protein sex hormone binding globulin (SHBG) and slightly less than one-third is bound to the protein albumin, the most abundant protein in the blood. A small percent (less than 4%) circulates as free (not bound to protein) testosterone. Free testosterone plus the testosterone that is bound to albumin is the testosterone that can act on target tissues. This is called bioavailable testosterone.
In many cases, measurement of total testosterone provides a healthcare practitioner 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.
The testosterone test may be used, along with tests for other hormone levels, to help evaluate conditions such as:
Testosterone testing may be used to monitor transgender individuals who are undergoing hormone therapy.
In men, the test may be ordered when infertility is suspected or when you have a decreased sex drive or erectile dysfunction. Some other symptoms of low testosterone include lack of beard and body hair, very small testicles, decreased muscle mass, and development of breast tissue (gynecomastia).
In boys with delayed or slowly progressing puberty, or very early puberty, the test is often ordered with the FSH and LH tests. Although there are differences among boys as to when puberty begins, it is generally between ages 9 and 14. Testing may be ordered when these common physical signs of puberty in boys developer early or later:
In females, testosterone testing may be ordered when you have irregular or no menstrual periods (amenorrhea), are having difficulty getting pregnant, or appear to have masculine features, such as excess facial and body hair, male pattern baldness, and/or a low voice.
In infants, testosterone testing may be ordered when the genitals are not clearly male or female.
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, usually starting after age 30. This is a normal part of aging and typically doesn't cause health problems.
A low testosterone level (male hypogonadism) may be due to:
(For more information, see the article on Low Testosterone in Adult Men.)
Increased testosterone levels in males can indicate:
In women, testosterone levels are normally much lower than in males, and there are different ranges of normal for women than men. Increased testosterone levels can indicate:
Most testosterone (up to 98%) circulates in the blood bound to proteins. A small amount of testosterone (less than 4%) circulates in the blood as free testosterone—it is not bound to protein. The bound plus unbound (free) testosterone is measured by labs as total testosterone.
Slightly less than one-third of the protein-bound testosterone is loosely bound to albumin, the main protein in the fluid portion of the blood. About two-thirds is tightly bound to another protein called sex hormone binding globulin or SHBG. The binding between testosterone and albumin is not very strong and is easily reversed. The free testosterone plus the albumin-bound testosterone is the bioavailable testosterone (BAT), which is the portion of testosterone that is available to act on target tissues.
In many cases, measurement of total testosterone provides a healthcare practitioner 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. Decreased SHBG levels may be seen in obesity, hypothyroidism, androgen use, and nephrotic syndrome (a form of kidney disease). Increased SHBG levels may be seen with low testosterone production, cirrhosis, hyperthyroidism, and estrogen use.
Depending on the reason for testing, other tests and hormone levels may be done in addition to testosterone testing. Some examples include:
Men who are diagnosed with consistently low testosterone levels and have related signs and symptoms may be prescribed testosterone replacement therapy to improve signs and symptoms. The American Urological Association recommends prescribing treatment only to men who meet the clinical and laboratory definitions of low testosterone. Testosterone replacement therapy may not be appropriate for everyone with a diagnosis of low testosterone. For example, the Endocrine Society recommends against routine replacement therapy for men over 65 and suggests making individualized treatment decisions for aging men. Treatment may also be inappropriate for individuals with certain health problems, such as prostate cancer or sleep apnea.
Some of the benefits and risks of hormone replacement therapy remain unclear and are the subjects of active research. It is important for you to talk to your healthcare practitioner about expectations for treatment and the potential side effects. Also read the Hormone Health Network patient guide Truth About Testosterone Therapy.
There is not much that can be done to naturally increase testosterone levels. However, healthy lifestyle choices, including regular exercise, good nutrition, maintaining a healthy weight and avoiding use of illicit drugs and/or excess alcohol, can help keep testosterone levels within a normal range. You may wish to talk to your healthcare practitioner about identifying and treating any underlying conditions or use of medications that might be contributing to your symptoms.
Women's bodies also produce testosterone but in small amounts. It is needed for hormonal balance and to help women's bodies to function normally. If your body is producing too much testosterone, you may have more body hair than average, have abnormal or no menstrual periods, or be infertile. A testosterone test, in conjunction with measuring other hormone levels, can help your healthcare provider to understand what is causing your symptoms.
Some healthcare practitioners may order testosterone levels for transgender individuals to determine whether blood levels have reached or stabilized at target male ranges. Your healthcare practitioner can help explain the meaning of your test results. For more on this topic, visit the Hormone Health Network article on Transgender Health and Mayo Clinic’s article Masculinizing Hormone Therapy.
Yes, there are different methods that labs may use to measure testosterone, and there are reasons for using different methods.
Alcoholism in males can decrease testosterone levels. Drugs, such as androgens other than testosterone, 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.
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