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.
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.
Gynaecomastia can have several causes.
Gynaecomastia can be caused by an imbalance between the sex hormones testosterone and estrogen. Estrogen causes breast tissue to grow. While all men produce some estrogen, they usually have much higher levels of testosterone, which stops the estrogen 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.
Some growth in breast tissue is not due to extra body fat from being overweight, so losing weight or doing more exercise may not improve the condition. However, a common reason for gynaecomastia is that being very overweight can increase levels of estrogen, which can cause breast tissue to grow.
During puberty boys hormone levels vary. If the level of testosterone drops, estrogen 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 estrogen to be produced. These changes in hormone levels can lead to excess breast tissue growth.
In rare cases, gynaecomastia can be caused by:
