Testosterone is a male sex hormone, also called an androgen, which is responsible for the development of masculine characteristics among men. In women, testosterone plays a role in muscle and bone development, energy levels and the distribution of fat. Normal testosterone levels for adult males are between 270 and 1,080 nanograms per deciliter (ng/dL) for men age 20 to 40; 350 to 890 ng/dL for men 40 to 60 years; and 350 to 720 ng/dL for men over 60. Women have lower levels of testosterone, and the average amount for a premenopausal woman is between 10 and 70 ng/dL. The normal amount for a postmenopausal woman is 7 to 40 ng/dL.
Identification
In men, testosterone is produced by the testes and the adrenal glands and in women it is produced in smaller amounts by the ovaries. The amount of testosterone production is controlled by the brain, specifically the pituitary gland. This gland secretes luteinizing hormone, a substance that tells the body to produce testosterone. When testosterone levels run low, the pituitary gland increases luteinizing hormone production, which in turn causes the testes or the ovaries to produce more testosterone.
Symptoms
Low testosterone levels may be difficult to identify if symptoms are not obvious or are confused with another disorder. Symptoms of low testosterone levels can also be related to the cause. For example, if low levels are the result of testicular inflammation, there may be scrotal pain and tenderness in addition to hormone changes. Symptoms of low testosterone levels include decreased libido, low muscle tone, erectile dysfunction, depression and lack of energy.
Disease
According to the UCLA Health System, low testosterone is also known as hypogonadism, and low levels can be the result of a disease process or medications. Diseases that affect the testicles or adrenal glands in men or the ovaries in women can cause low testosterone levels. Some examples include Addison's disease, chronic alcohol consumption, liver disease; steroid use and estrogen therapy.
Age
Low testosterone may also be the result of age, as boys have lower levels before entering puberty. Overall testosterone levels decline with age, particularly after 75. Some genetic disorders also cause low testosterone levels; including Klinefelter's syndrome, a condition that occurs when a boy is born with an extra X chromosome; undescended testicles; and hemochromatosis, a condition that causes the body to overproduce iron.
Considerations
See your doctor if you feel you may have low testosterone levels. According to the American Diabetes Association, a test called the ADAM Questionnaire can help you identify if you might have low testosterone levels. The questionnaire asks about symptoms of low energy, low sexual drive and depressed mood. You can take the test and contact your doctor with the results. A blood test is also available that can check for testosterone levels in the bloodstream.
