Adolescence is a time of rapid growth in height and weight and of physical changes throughout the body. Most of these changes occur near the time of puberty, which in the United States and Canada usually begins for girls between the ages of 9 and 11, and for most boys between the ages of 9½ and 13.
Breast buds-slight elevation and enlargement of the nipple area-are one of the first signs of puberty in girls. Also, pubic hair usually starts growing around the same time. In boys, the first sign of puberty is that the testicles increase in size, followed by the growth of pubic hair and by penis lengthening.
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Girls usually grow rapidly during early puberty. Then growth slows down with the first menstrual period (menarche), which most commonly happens sometime between ages 11 and 14. (It can happen as early as age 9 or up to age 15.) For boys, the height spurt occurs after other signs of puberty have developed. While boys lag behind girls in height in early adolescence, they typically end up being taller than girls. This happens because after growth starts, boys grow at a faster rate and for a longer period of time. Girls reach their approximate adult height around 16 years of age, and boys at about 18 years of age.1
There has been a long-term trend toward earlier puberty and larger growth related to better health and nutrition. Also, race seems to affect the timing of puberty. For example, African American and Mexican American girls may have breast development earlier than Caucasian girls.
The surging hormones related to puberty often stimulate the sex drive in both males and females. It is normal for members of both genders to masturbate in private. Hormones may also trigger episodes of difficult behavior, such as challenging parents and other authority figures.
Growth in body parts may occur out of sync with each other. For example, the nose, arms, and legs may grow faster than the rest of the body. Other physical development during puberty usually includes: