Description
Testosterone testing is used to diagnose several conditions in men, women, and boys. These conditions include:
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delayed or precocious (early) puberty in boys;
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decreased sex drive in men and women;
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erectile dysfunction in men;
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infertility in men and women;
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testicular tumors in men;
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or pituitary disorders; and
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hirsutism and virilization in girls and women.
When is it ordered?
In males, the test is ordered, often along with the FSH and LH tests, if puberty is delayed or slow in developing. Although there are differences from individual to individual as to when puberty begins, generally by the age of 10 years, there are hormonal and physical manifestations of the onset of puberty in males. Some symptoms of delayed puberty may include:
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Delayed development of muscle mass
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Lack of deepening of the voice or growth of body hair
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Slow or delayed growth of testicles and penis
A delay can occur if the testes do not produce enough testosterone or if the pituitary does not produce enough LH. 

The test also can be ordered if 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 if the patient has a decreased sex drive or erectile dysfunction, all of which can result from low testosterone levels. Some other symptoms include lack of beard and body hair, decreased muscle mass, and development of breast tissue (gynecomastia).
In females, testosterone testing may be done if a patient has irregular or no menstrual periods (amenorrhea), is having difficulty getting pregnant, or appears to have masculine features, such as facial and body hair, male pattern baldness, and 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).