Ah, puberty. It can be a very interesting time in a guy's life, what with all the changes going on. In fact, it seems like every day something on your body grows bigger or hair begins sprouting somewhere. Each day brings a new change or two, and it can sometimes feel like it's hard to keep up.

It doesn't happen to every guy, but one of these changes can be the development of breast tissue. It's called gynecomastia (pronounced: guy-nuh-ko-mas-tee-uh) and it's completely normal — and almost always temporary. So how exactly does a guy happen to develop breast tissue?

What Is Gynecomastia?

Gynecomastia is a condition in which breast tissue forms in guys, usually due to normal hormonal changes during puberty. Hormones are chemicals produced by your body's glands. In a guy, hormones produced in the testicles are responsible for the physical changes that begin to take place during puberty — facial hair, muscle development, a deepening of the voice, and the lengthening of the penis, for example. Guys and girls produce both androgens (hormones that help develop and maintain male characteristics) and estrogen (a hormone that is responsible for most female characteristics).

Guys have mostly androgens in their systems, but they also have small amounts of estrogen. In girls, breast growth is caused by high levels of estrogen. Normally, when going through puberty, a guy's production of androgens increases significantly, whereas estrogen production remains low.

However, sometimes guys produce enough estrogen during puberty that some breast tissue develops. Breast tissue growth in guys can appear on one or both sides of the chest, and the breast area can feel tender. This doesn't mean you're turning into a girl or anything. It's just a minor change in your hormones as you begin to grow into adulthood.

How Common Is It?

It's estimated that about half of all males going through puberty experience some degree of gynecomastia in one or both breasts. Gynecomastia is almost always a temporary condition, and it's very unusual for the breasts to stay developed — they will eventually flatten out completely within a few months to a couple of years. It usually goes away on its own and no medical treatment or surgery is needed.

Even though it's just a temporary change for most teens, some guys with gynecomastia feel embarrassed or self-conscious about their appearance. Many guys find that wearing loose-fitting shirts helps make the condition less noticeable until the breast tissue shrinks over time. Surgical removal of the breast tissue is an option in some cases. If a guy finds his gynecomastia is bothering him, he can talk to a doctor about it.

Although the most common cause of gynecomastia is puberty, it can sometimes be caused by certain diseases or side effects of some medications. Using illegal drugs such as anabolic steroids, marijuana, or heroin can also disrupt hormonal balance and lead to gynecomastia.

There's also something called pseudogynecomastia (or false gynecomastia). This has nothing to do with puberty or hormones. It's just simply due to the fact that some guys have extra fat in the chest area, making it look like they have breasts. A doctor's exam can tell whether a guy has gynecomastia or pseudogynecomastia.

If you're concerned or have any questions about gynecomastia, talk to your doctor. Keep in mind that temporary breast tissue growth in guys is a common part of puberty that will usually go away on its own.

Reviewed by: Steven Dowshen, MD
Date reviewed: April 2010