What is testosterone?

Testosterone is a sex hormone that helps develop the male reproductive system including the penis, testes and prostate.

Males and females both naturally produce testosterone, though males produce far more than females. In males, most testosterone is made by the testes. In females, testosterone is made by the ovaries and converted to female sex hormones. It is also produced in the adrenal glands in both males and females.

Testosterone levels can vary greatly depending on your sex, age and health. Children usually have lower levels of testosterone that increase around puberty. In adults, levels gradually reduce with age.

What does testosterone do?

Testosterone is important in the development of the male reproductive organs, such as the testicles and penis.

It is responsible for the changes during puberty in males, such as:

• body hair
• a deeper voice
• stronger muscles
• growth spurts
• penis growth
• acne

In adult males, testosterone carries out important body functions, such as:

• regulating sex drive and mood
• regulating bone and muscle strength
• making new blood cells
• helping the testes make sperm

In females, testosterone is needed for bone and muscle strength and sex drive. Some of it is converted to a form of oestrogen.

What causes low testosterone?

Your body needs to maintain normal levels of testosterone for it to function properly.

Testosterone levels are controlled by a feedback loop between your brain, your pituitary gland and your testes. Sometimes your body can't make enough testosterone. This could be because your testes are not working properly, or because the pituitary gland in your brain is not telling your testes to make testosterone.

A low testosterone level is also known as androgen deficiency or hypogonadism.

There are many reasons that you may have low testosterone levels. Causes of low testosterone levels include:

• damage to your testicles — for example by an injury, undescended testes or an infection, such as mumps
• damage to your pituitary gland
• obesity
• genetic conditions, such as Klinefelter syndrome (XXY)
• chronic health conditions, such as diabetes and haemochromatosis
• tumours
• some medicines and cancer treatments

Low testosterone with ageing

Healthy older males may have lower testosterone levels due to the ageing process itself. This is generally not a medical concern.

Some people use the term 'andropause' or 'male menopause' to refer to the decline in testosterone with ageing. This term is misleading. It suggests that males don't have enough testosterone as they get older, however there is no clear evidence that this is a problem in healthy people.

You may have a greater drop in your testosterone levels if you have long-term medical conditions or if you are living with obesity. If low testosterone is a problem for you, you may want to speak to your doctor about whether it is simply because you are getting older or if there is another cause.

Use the BMI Calculator to find out if your weight and waist size are in a healthy range.

Low testosterone in females

The level of testosterone in females declines gradually until menopause. Lower levels of testosterone can also be due to:

• oral contraceptive pill use
• oral steroid therapy
• some medicines
• conditions that affect the pituitary gland

What are the symptoms of low testosterone?

Males with low testosterone levels can have many different symptoms. You might have:

• reduced libido
• problems getting and keeping erections
• changes in sleep patterns and poor sleep
• hot flushes
• lower energy levels
• low mood
• difficulty concentrating or remembering things

You may notice physical changes such as:

• increased body fat
• reduced muscle bulk and strength
• swollen or tender breasts
• less facial and body hair growth

You may also find out that you have infertility or decreased bone density.

Children with low testosterone levels might:

• have a small penis or testes
• have late puberty
• not grow facial or body hair or their voice might not break

Some females with low testosterone levels might have loss of libido.

When should I see my doctor?

If you think that you have any of the symptoms of low testosterone you should talk to your doctor. They will ask you about your medical history, perform a physical examination and send you for a blood test. They may then refer you to an endocrinologist — a doctor who specialises in hormones.

If you are having difficulty becoming pregnant, you may want to talk to your doctor about the possibility of low testosterone levels.

How can I get my testosterone levels tested?

Your doctor can check your testosterone levels with a blood test, along with other hormones that might affect them. Testosterone levels can vary, so if you have a low level on one blood test, a second test is needed to confirm low levels.

It's best to have the blood test early in the morning while you are fasting. This is when your testosterone levels are usually at their highest.

Your doctor may also want to measure your iron levels to check for haemochromatosis. They may refer you for a genetic test called a karyotype to check for genetic conditions such as Klinefelter's syndrome.

How is low testosterone treated?

If you have low testosterone, you can take testosterone replacement therapy. This is given by injections, gels, creams or tablets. Gels, creams and tablets are usually taken daily whereas injections are given every 3 months.

If there is an underlying cause for your low testosterone, it should be treated. You may also need testosterone therapy.

It's unclear whether testosterone therapy has any benefit for older males who have low testosterone but no testicular or pituitary problems. Getting diabetes or other health conditions under control and losing weight can improve testosterone levels.

If you are taking testosterone therapy, your doctor will regularly monitor your testosterone levels with blood tests. They may also check your bone health.

If you have prostate or breast cancer, or are planning to try to have a child, your doctor won't prescribe testosterone therapy. If you have fertility problems because of low testosterone levels, speak to your doctors about fertility treatments and other options.

You can also increase your testosterone levels by:

• getting regular exercise
• keeping stress to a minimum
• eating a healthy diet
• losing weight if you live with overweight or obesity

What are the complications of low testosterone levels?

If you have low testosterone levels, you are at a higher risk of developing osteoporosis and breaking your bones.

Testosterone replacement therapy can also cause side effects and complications, such as:

• acne or other skin reactions
• male pattern hair loss
• higher levels of red blood cells and prostate-specific antigen (PSA)
• reduced fertility in some people

Resources and support

Visit Healthy Male for more information about male reproductive and sexual health

Pathology Tests Explained also has more information on blood tests, including testosterone tests.

Talk to your doctor or call healthdirect on 1800 022 222 at any time to speak to a registered nurse (known as NURSE-ON-CALL in Victoria) for more information and advice.

Do you prefer to read in languages other than English?

Hormones Australia provides resources on hormone conditions, available in various languages.

Looking for information for Aboriginal and/or Torres Strait Islander people?

Find an Aboriginal Community Controlled Health Organisation (ACCHO) in your area.