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Changes During Puberty for Boys and Girls

What is puberty? Growing up. Everyone goes through the same process. Whether you start at age 9 or at age 15, it’s all “normal.’’ You are still you inside. Your body and feelings are changing at their own pace. Growing up can be a great experience: a time of changing and finding out who you are. Hormones are responsible for the changes you are beginning to notice. In boys, testosterone is the hormone. In girls, it's estrogen. Girls may start normal puberty as early as age 7 or not start at all until age 15. For boys it is usually anywhere between ages 9 and 15.

Girls

Three girls showing differences in development at age 12.

Three girls showing differences in development at age 15.

Three girls showing differences in development at age 18.

At 12, you may have a young girl's body or begin to look like a woman.

At 15, you'll see less difference between you and your friends.

At 18, you'll pretty much have your adult body.

Breasts come in all shapes and sizes. Some girls’ breasts grow early; others grow late. Most girls have one breast that grows faster than the other. Breast growth will be the first sign that puberty has started.

Boys

Three boys showing differences in development at age 12.

Three boys showing differences in development at age 15.

Three boys showing differences in development at age 18.

At 12, you'll probably still have a young boy's body.

At 15, you might look like a child or a young man: either one is normal.

At 18, you'll see less difference between you and your friends.

An erection is the swelling and stiffening of your penis. Erections don’t only happen in sexual situations. It’s also normal to get a “hard on’’ just from your pants rubbing against you.

Online Medical Reviewer: Liora C Adler MD
Online Medical Reviewer: Pat F Bass MD MPH
Date Last Reviewed: 10/1/2016
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