Low testosterone in boys and men Taiaki tāne hakahaka

Testosterone is a sex hormone made in your testicles. While your body will naturally reduce testosterone production with age, some people have unusually low levels.

This may be caused by a range of things that can affect the testicles' ability to make testosterone.

A problem with your testicles such as:

• something you were born with (like undescended testicles that are not corrected)
• an injury
• an infection (like mumps)

A general medical problem such as:

• diabetes
• haemochromatosis — a condition where the body absorbs and stores too much iron
• being an unhealthy weight
• obstructive sleep apnoea

A problem with part of your brain (pituitary gland or hypothalamus), which mean your brain does not produce enough of the hormones that cause the testicles to produce enough testosterone.

Cancer treatment including:

• chemotherapy
• radiotherapy

Some medications and supplements such as:

• opiate pain killers
• anabolic steroids (a synthetic version of testosterone) used by some bodybuilders and professional athletes to support muscle growth.

Symptoms of low testosterone vary depending on your age and how long the levels have been low.

If a boy has never had enough testosterone, they may not fully develop during puberty. They may have:

• a lack of body hair
• small testicles
• smaller muscles.

Short‑term effects in adults include:

• low sex drive
• poor erections (impotence)
• low sperm count
• breast enlargement.

Longer term, low testosterone can cause:

• loss of body hair
• loss of muscle strength
• more body fat
• low energy.

Having low levels of testosterone can increase your risk of:

• heart disease
• stroke (cardiovascular disease)
• cause weak and thin bones (osteoporosis).

It can make it difficult to conceive a baby (infertility) by reducing sperm production but does not always do this.

Low testosterone can also have psychological effects.

Your healthcare provider will ask about you and your symptoms. They will also check:

• the amount of body hair you have
• the size of your penis and testicles.

You will need to have a blood test to check the amount of testosterone in your blood. This test needs to be done early in the morning as this is when blood testosterone levels are naturally at their highest. If it shows a low level, you will need a second test on another day to confirm it.

Since some medications and supplements can cause low testosterone, it is important you tell your healthcare provider about any that you are taking. This includes any sports supplements and herbal medications.

If you need it, you will have testosterone replacement with testosterone tablets, patches or injections.

The type and dose of the treatment varies based on your needs.

The aim is to get your testosterone back to normal levels, which will help reverse symptoms. Testosterone replacement treatment may:

• deepen your voice
• help you grow a beard and pubic hair
• improve your sex drive and erections
• strengthen your muscles and bones.

Before having testosterone treatment, your red blood cell count will be checked. You will need this test once a year as testosterone treatment can increase your red blood cell level.

Testosterone treatment could be dangerous if you have, or have had, prostate cancer. Your healthcare provider will talk to you about whether you need to be checked for this or whether you need regular monitoring.

It can also make heart failure worse if you have it.

Other possible side effects of testosterone replacement include:

• acne
• swelling of breast tissue
• mood changes including increased anger
• shrinking of testicles.

If you notice any of these side effects you should talk to your healthcare provider.