What physical changes take place in adolescence?

Unlike middle childhood, which is a period of predictable and gradual change, adolescence is a time of abrupt and dramatic transformation. To start with, there are tremendous physical changes. The child becomes an adult and the body dramatically changes form, frequently leaving young adolescents surprised and disoriented by their new and alien body. “I didn’t know where my feet were,” one young man described his feelings, referring to the year he grew ten inches in about as many months. “And everyone wanted me to play basketball,” he added.

What physical changes take place in adolescence? Both boys and girls undergo tremendous growth spurts. While the typical American ten-year-old is about 4’7”, the median height for seventeen-year-olds is about 5’8” for boys and 5’4” for girls. The shape of the body changes as well, with lengthening of the trunk, arms and legs and enlargement of the hands and feet. The face also changes, with growth of the nose, jaw, and cheekbones. Often the ears and nose grow before the rest of the face. In North American girls, the growth spurt starts around ten and is completed by about age sixteen. In North American boys, the growth spurt begins around twelve or thirteen and is completed by about seventeen or eighteen. Most adolescents add about ten inches in height and gain about fifty to seventy-five pounds. Additionally, there are tremendous hormonal and physiological changes associated with puberty.

During puberty, the body transforms into a sexually mature state, with the adolescent now capable of sexual reproduction. This takes place about two years earlier in girls than in boys. Girls start puberty around age twelve and complete it in about four years. In both sexes, a flood of hormones is released by various glands in the body. Growth hormone and thyroxine stimulate the increase in body size.

For boys, most of the hormones are released by the testes. The androgen (or male hormone) testosterone leads to muscle growth, body and facial hair, and the development of male sexual characteristics. Boys also release a small amount of estrogen, which stimulates release of growth hormone. This in turn stimulates growth in body size and bone density. By the end of puberty, boys have developed greater muscle mass than girls and their shoulders have widened relative to their waist and hips.

In girls, hormones are released from the ovaries. Estrogen release results in maturation of the breasts, uterus, and vagina, an accumulation of body fat, and an increase in the hip to waist ratio. In girls but not boys, androgen release from the adrenal glands (right above the kidneys) results in increased height as well as the growth of pubic and underarm hair. Menarche, the beginning of menstruation, begins around age 12.5, although this can vary widely depending on many factors, including diet.