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Low testosterone

In this series:Erectile dysfunction

Low testosterone in men (testosterone deficiency) is often part of the ageing process and therefore common in older men. It can also occur at any age as a result of conditions affecting the testicles or the pituitary gland in the brain.

Low testosterone can be treated with testosterone replacement therapy. Any underlying cause for the testosterone deficiency will also need treatment. The outlook will depend on the underlying cause.

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What is low testosterone?

Low testosterone (testosterone deficiency) in men occurs when the body is unable to make enough testosterone. It is sometimes called hypogonadism. Low testosterone can significantly affect a man's health and quality of life.

Testosterone is the most important sex hormone in men. Its production is controlled by both the brain and the testicles (testes). The body starts to produce testosterone during puberty. From the age of about 30 years, testosterone levels usually start to decrease.

Testosterone is essential for developing and maintaining male characteristics. Testosterone also has effects on sexual function. Low testosterone levels increase a man's risk of developing disease of the heart and blood vessels (cardiovascular disease), and increase the risk of early death.

What causes low testosterone?

Low testosterone can be caused by normal ageing. However, there are other potential causes of low testosterone. Some causes can be inherited. Low testosterone may be present at birth or it may develop later in life.

Being significantly overweight or obese at any age is linked to low testosterone.

Testosterone levels can reduce due to a physical illness, surgery or emotional stress, but in these situations the testosterone level will go back to normal once the underlying problem has been treated.

Primary testosterone deficiency

Low testosterone may be caused by a failure of the testicles (testes) to make enough testosterone. This is sometimes called primary testosterone deficiency. Common causes of primary testosterone deficiency include:

  • Klinefelter's syndrome. A male normally has one X and one Y chromosome. In Klinefelter's syndrome, two or more X chromosomes are present in addition to one Y chromosome.

  • Undescended testicles. This is where a baby is born without one or both of his testicles in the scrotum. They are usually in the lower part of the pelvis but have failed to migrate into the scrotum. If they have not descended by 6 months of age then surgery is needed to bring them into the scrotum. Testicles need to be slightly cooler than normal body temperature in order to function well. If the testicles remain inside the body rather than the scrotum they will be too warm and this reduces their ability to produce testosterone.

  • Mumps orchitis. This is where there is an inflammation of the testes due to the mumps infection (which can largely be prevented by immunisation with the MMR vaccine).

  • Haemochromatosis. This is an inherited condition causing high iron levels to build up.

  • Injury to the testicles.

  • Cancer treatment. Both chemotherapy or radiotherapy can interfere with testosterone and sperm production.

Secondary testosterone deficiency

Low testosterone can also be caused by a problem with parts of the brain (hypothalamus and pituitary gland) which make the hormones that stimulate the testicles to make testosterone. This is sometimes called secondary testosterone deficiency. See the separate leaflet called Pituitary Gland Disorders for further information.

In secondary testosterone deficiency, the testicles are normal but don't function properly because of a problem with the pituitary gland or hypothalamus. A number of conditions can cause secondary testosterone deficiency, including:

  • Pituitary gland disorders such as a benign tumour called a prolactinoma.

  • HIV/AIDS: can cause low levels of testosterone by affecting the hypothalamus, the pituitary gland and the testicles.

  • Some medicines (such as opiate painkillers and some hormones): can affect testosterone production.

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How common is low testosterone?

Men are more likely to develop low testosterone as they get older. It is also more common in men who are overweight and men who are in poor general health with long-term health conditions.

One large study in Europe found that testosterone deficiency affected about 2 in 100 men aged 40 to 79 years. Testosterone deficiency affected about 5 in 100 men aged 70 to 79 years.

Low testosterone symptoms

The symptoms will depend on when the condition develops.

If an unborn male baby does not produce enough testosterone during the pregnancy then the testicles won't develop properly and the baby may be born with either:

  • Female genitals.

  • Genitals that are neither clearly male nor clearly female (ambiguous genitals); or

  • Underdeveloped male genitals.

In adult males, low testosterone may cause:

If testosterone deficiency develops before puberty then it may also cause:

  • Delayed puberty.

  • Lack of deepening of the voice.

  • Impaired growth of the penis and testicles.

  • Excessive growth of the arms and legs compared with the trunk of the body.

As testosterone levels decrease in older men, some men experience symptoms similar to those of the menopause in women, such as:

  • Excessive tiredness (fatigue).

  • Decreased sex drive (reduced libido).

  • Difficulty concentrating.

  • Hot flushes.

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How to test for low testosterone

Many older men with low testosterone are never diagnosed. Problems such as tiredness, low sex drive and erectile dysfunction can be thought to be due to the normal ageing process so medical help is often not sought.

Testosterone deficiency can be identified by blood tests which might be suggested when describing decreased sex drive (reduced libido) or erectile dysfunction.

Men who don't respond to the medicines that are used to treat erectile dysfunction (such as sildenafil), should also have their testosterone level checked.

If tests confirm a low testosterone level, referral to a urologist or andrology specialist would usually be suggested. They can offer further testing to determine if a problem with the testicles (testes) or a pituitary gland abnormality is the cause. These further tests may include:

Treatment of low testosterone

Can low testosterone be prevented?

Early detection in boys can help prevent problems from delayed puberty. Testosterone treatment can stimulate puberty and the development of sex characteristics, such as increased muscle mass, beard and pubic hair growth, and growth of the penis.

Early diagnosis and treatment in adult men provides better protection against loss of bone density (osteoporosis) and cardiovascular disease. Treatment can also improve tiredness, general well-being, erectile dysfunction and sex drive.

The treatment for low testosterone also depends on the underlying cause.

For men without another underlying cause, maintaining a healthy body weight is important. Obesity in young men is increasing and there has been shown to be an increased number of young men with low testosterone levels in the United States, resulting from obesity.

Testosterone replacement

Testosterone treatment is usually given in the form of a gel. Other forms of testosterone treatment include long-acting injections or using a patch applied to your skin.

Side-effects of testosterone replacement

Testosterone replacement has been shown to cause:

  • Worsening sleep apnoea.

  • Acne.

  • Benign prostatic hypertrophy (non-cancerous enlargement of the prostate gland).

  • Growth of prostate cancer (in men who already have prostate cancer).

  • Gynaecomastia (enlargement of breast tissue).

  • Shrinking of the testicles (testicular atrophy) and reduction in sperm count.

  • Red blood cell production over-development (which can lead to increased risks of blood clots in the legs or lungs).

  • Increased anger and aggression though not increased physical aggression.

  • Worsening of heart failure (in men who already have heart failure).

There are concerns about possible increased risks of heart disease and possible risks of prostate cancer development - neither of which have been clearly shown in studies to date.

Testosterone replacement is contra-indicated (not allowed) in patients with male breast cancer, prostate cancer, men with severe heart failure, men with a very raised haematocrit (a marker of red blood cell production) and men actively wanting to conceive a child in the future.

Other treatments

If low testosterone is caused by a pituitary gland problem, treatment with pituitary hormones may stimulate sperm production and improve fertility. Testosterone replacement therapy can be used.

If a pituitary tumour is the cause of low testosterone then this will require treatment, such as surgical removal, chemotherapy or radiotherapy, as well as replacement therapy with other hormones.

Although there's often no effective treatment to restore fertility in a man with primary testosterone deficiency, infertility treatments may be helpful.

What is the outlook?

There have been many studies looking at the benefits or otherwise of treating low testosterone levels with testosterone replacement. The results of these are mixed.

A large review of more than 150 studies in 2016 showed that there was no evidence of benefit of testosterone replacement for heart disease (and some evidence for increased cardiac events), no significant benefit of testosterone on libido and no consistent benefit on mood or cognitive function. The majority of studies showed that testosterone increased muscle mass but did not have an effect on muscle strength or function. That review said that the evidence from randomised control trials was said not to support treatment for physical function, sexual function, mood or cognition.

Subsequent reviews have been more positive with evidence of benefit of testosterone for libido and mood. Studies also tend to show that testosterone can be of benefit in improving symptoms of erectile dysfunction when used alongside medications such as sildenafil in men who had no response to sildenafil (or other similar medications) alone. There was little evidence of testosterone treatment alone being of significant benefit.

It is thought that some of the apparent benefits of testosterone might be related to healthier men generally being more aware of their bodies and being more likely to be prescribed testosterone.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

  • Next review due: 12 May 2028
  • 8 Jun 2023 | Latest version

    Last updated by

    Dr Pippa Vincent, MRCGP

    Peer reviewed by

    Dr Colin Tidy, MRCGP
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