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 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 the body changes, this can cause a man's breasts to grow. Sometimes, the cause of this imbalance is unknown.
Being very overweight (obese) is a common cause of gynaecomastia – this is because being overweight can increase levels of oestrogen, which can cause breast tissue to grow. If you're overweight you're also more likely to have excess fat that can enlarge the breast tissue. For some people losing weight or doing more exercise can help but this may not always 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.
As men get older, they produce less testosterone. Older men also 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 rare causes of gynaecomastia include:
- side effects of medicine – such as anti-ulcer drugs or medicine for heart disease
- illegal drugs – such as cannabis or anabolic steroids
- drinking too much alcohol
- a health condition – such as kidney failure or liver disease
- Klinefelter syndrome (a rare genetic disorder)
- lumps or infection in the testicles
Treatment for gynaecomastia
See a GP if you're worried about breast tissue growth – they can discuss the treatment options with you.
If a GP thinks you need treatment, they may recommend:
- surgery to remove the excess breast tissue
- medication to adjust a hormone imbalance
Read 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've had gynaecomastia for a long time, it hasn't responded to other treatments and it's causing you a lot of distress or pain a GP may refer you to a plastic surgeon to discuss the possibility of surgery.
Always see a GP if the area is very painful or there's an obvious lump. Sometimes, the lump may need to be removed. Gynaecomastia isn't related to breast cancer, but you should see a GP if you're worried about breast swelling.
Read the answers to more questions about men's health.
Page last reviewed: 22 February 2018
Next review due: 22 February 2021