What is gynaecomastia?

Gynaecomastia (sometimes referred to as 'man boobs') is a common condition that causes boys’ and men’s breasts to swell and become larger than normal. It is most common in teenage boys and older men.

What are the signs of gynaecomastia?

Signs vary from a small amount of extra tissue around the nipples to more prominent breasts. It can affect one or both breasts.

Sometimes, the breast tissue can be tender or painful, but this isn’t always the case.

What causes gynaecomastia?

Gynaecomastia can have several causes.

Hormone imbalance

Gynaecomastia can be caused by an imbalance between the sex hormones testosterone and oestrogen. Oestrogen causes breast tissue to grow. While all men produce some oestrogen, they usually have much higher levels of testosterone, which stops the oestrogen from causing breast tissue to grow.

If the balance of hormones in his body changes, this can cause a man’s breasts to grow. Sometimes, the cause of this imbalance is unknown.

The growth in breast tissue is not due to extra body fat from being overweight, so losing weight or doing more exercise will not improve the condition.

Newborn baby boys

Gynaecomastia can affect newborn baby boys because oestrogen passes through the placenta from the mother to the baby. This is temporary and will disappear a few weeks after the baby is born.


During puberty, boys’ hormone levels vary. If the level of testosterone drops, oestrogen can cause breast tissue to grow. Many teenage boys have some degree of breast enlargement. Gynaecomastia at puberty usually clears up as boys get older and their hormone levels become more stable.

Older age

As men get older, they produce less testosterone. Also, older men tend to have more body fat, and this can cause more oestrogen to be produced. These changes in hormone levels can lead to excess breast tissue growth.

Other causes

In rare cases, gynaecomastia can be caused by:

  • side effects of medication, such as anti-ulcer drugs or medication for heart disease
  • illegal drugs, such as cannabis or anabolic steroids
  • drinking too much alcohol
  • a health abnormality, such as kidney failure or liver disease
  • Klinefelter’s syndrome, a rare genetic disorder
  • lumps or infection in the testicles

Treatment for gynaecomastia

If you’re worried about breast tissue growth, see your GP.

If your GP thinks treatment is needed, there are two types of treatment for gynaecomastia:

  • surgery to remove the excess breast tissue
  • medication to adjust a hormone imbalance

Your GP can discuss the treatment options with you. Find out more about male breast reduction surgery.

Procedures such as breast reduction surgery are not usually available on the NHS unless there is a clear medical need for them. For example, if you have had gynaecomastia for a long time, it has not responded to other treatments and it is causing you a lot of distress or pain, your GP may refer you to a plastic surgeon to discuss the possibility of surgery.

Always see your GP if the area is very painful or there is an obvious lump. Sometimes, the lump may need to be removed.

Gynaecomastia is not related to breast cancer but if worried about breast swelling, see a GP.

Read the answers to more questions about men’s health.

Further information:


Teen bodies

Find out about the changes that happen to boys’ and girls’ bodies during puberty.

Media last reviewed:

Next review due:

Page last reviewed: 04/04/2013

Next review due: 03/04/2015