To find out if testosterone levels are abnormal in a male or female patient. Measurement may help to explain why a man has difficulty in getting an erect penis (erectile dysfunction), the inability of your partner to get pregnant (infertility), premature or delayed puberty, or masculine physical features if you are women. In a women it is used to investigate polycystic ovarian syndrome (PCOS). More recently it has been used to investigate the so-called Male Menopause.
If you are man and your doctor thinks that you may be infertile or if you are unable to get or maintain an erection
If you are a boy with either early or delayed sexual maturity
If you are a female but have male traits, such as a low voice or excessive body hair (hirsutism), or are infertile or have no periods or if they are irregular
A blood sample taken from a vein in your arm
Testosterone is a steroid hormone (androgen) made by the testes in males. The production of testosterone is stimulated and controlled by luteinising hormone (LH), which is manufactured in the pituitary gland.
In men, testosterone stimulates the enlargement of the penis, growth of body hair, muscle development, and a deepening voice. It is present in large amounts in boys during puberty and in men to regulate the sex drive and maintain muscle mass.
In women testosterone levels are about one tenth of those in men. Testosterone is produced both in small amounts from the ovary and by conversion from other weak androgens in the body.
Testosterone is also produced by the adrenal glands in both men and women.
How is the sample collected for testing?
A blood sample is taken by needle from a vein in the arm.
There is no preparation e.g. fasting required for this test.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
How is it used?
Testosterone testing is used to diagnose several conditions in men, women, and boys. These conditions include:
- delayed or early (precocious) puberty
- decreased sex drive
- erectile dysfunction
- excessive body hair, also called hirsutism
- ovarian tumours
Men and women
- adrenal tumours
- Hypothalamic and pituitary disorders
When is it requested?
In boys, the testosterone is measured with the FSH and LH tests, if puberty is delayed or slow in developing. Although puberty begins at different times in different individuals, generally by the age of 10 years, there are hormonal and physical manifestations of the onset of puberty. A delay can occur if the testes do not produce enough testosterone or if the pituitary does not produce enough LH.
The test may be performed if a young boy seems to be undergoing a very early (precocious) puberty with obvious secondary sex characteristics, such as an enlarged penis, development of muscle mass, deepening voice and growth of body hair.
In men, the test may be performed when infertility is suspected or if the patient has a decreased sex drive or erectile dysfunction, which can result from low testosterone levels.
In women, testosterone may be measured if a patient has irregular or no menstrual periods (amenorrhoea), 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 tumours 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?
There is great variability in testosterone levels in men and it is normal for testosterone levels to fall as men get older.
In males, a low testosterone level may be due to hypothalamic or pituitary disease with reduced production of LH and FSH, or damage to the testes with reduced production of testosterone. Genetic diseases can cause decreased testosterone production in young men (Klinefelter’s, Kallman’s, and Prader-Willi syndromes) or testicular failure and infertility (as in myotonic dystrophy, a form of muscular dystrophy). A decreased testosterone level also can indicate impaired testosterone production because of acquired damage to the testes, such as alcoholism, physical injury, or viral diseases like mumps. Use of most anabolic steroids also causes a decrease in testosterone levels.
Increased testosterone levels in males can indicate testicular tumours . Increased testosterone in boys is usually the cause of early puberty.
In women, increased testosterone levels can indicate polycystic ovary syndrome (PCOS) or an ovarian or adrenal gland tumour.
Is there anything else I should know?
If I have a low testosterone level, will taking supplemental testosterone help?
Maybe. Testosterone supplements, either with patches or injections, can raise testosterone levels. However although men with erectile dysfunction may have low testosterone, testosterone administration does not improve the symptoms in all cases. Your doctor will determine if this is the right therapy for you.
I am a woman, so why do I need a testosterone test?
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, however, you may have more body hair than average, have abnormal or no menstrual periods, or be infertile. A testosterone test, together with other tests, can help your doctor to understand what is causing your symptoms.
Is the amount of body hair directly proportional to the amount of testosterone in my body?
Studies have shown a proportional relationship of testosterone levels to the amount of body hair. However, the hair growth response to testosterone differs in different parts of the body. Hence, in some men, for example, testosterone promotes hair growth in the abdomen and back while hair growth is suppressed in the scalp, leading to male pattern baldness.
What are free and bioavailable testosterone?
Most of the testosterone in the blood circulates bound to two main proteins, albumin and sex hormone binding globulin (SHBG). Only a small amount of testosterone (1-4%) is not bound and is ‘free’. The free testosterone is available to tissues. Testosterone is loosely bound to albumin and this proportion may also be available to tissues. Both free and bioavailable testosterone provide a measure of the amount of testosterone available to tissues and they give the same information. Free testosterone is calculated from the testosterone and SHBG results whereas bioavailable testosterone is a separate measurement.
The amount of free and bioavailable testosterone is affected by the levels of SHBG. High levels of SHBG are caused by cirrhosis of the liver, anti-convulsant therapy, oestrogen therapy and hyperthyroidism. Low levels are present in hypothyroidism, androgen use, nephritic syndrome, polycystic ovarian syndrome and obesity. In these situations the measurement of free or bioavailable testosterone may be more helpful in diagnosis.
On This Site
Tests: FSH, LH, SHBG, DHEAS, Estradiol (see Estrogens), Dihydrotestosterone (DHT), Gonadotropin-releasing Hormone, Semen Analysis, Anti-Mullerian Hormone, Androstenedione
Conditions: Infertility, PCOS, Endocrine Syndromes, Testicular Cancer, Adrenal Insufficiency, Congenital Adrenal Hyperplasia
Elsewhere On The Web
The Hormone Health Network: Men's Health
Mayo Clinic: Infertility
Mayo Clinic: Testosterone therapy
KidsHealth.org: Precocious puberty
KidsHealth.org: Delayed puberty
MedlinePlus Medical Encyclopedia: Congenital Adrenal Hyperplasia