Physical Development: What’s Normal? What’s Not?

Two boys exactly the same age can begin or complete puberty years apart, yet still fall within the broad parameters of “normal” growth. The timing and pace of a child’s physical development varies greatly, because it is determined largely by the genetic programming that he inherited from his parents. For a boy or girl to be slightly less developed or more developed than other kids the same age rarely warrants cause for alarm. But if a youngster seems significantly outside the norm, parents should raise their concerns with their pediatrician, so that he can evaluate for—and most likely rule out—any medical disorders. Chances are, it’s the doctor who will bring this to the parents’ attention.

Whatever timetable a teen’s growth pattern follows, it is during adolescence that your son or daughter grows more rapidly than at any time of life except infancy. On average, a girl’s growth spurt occurs around age eleven and a half, but it can begin as early as eight or as late as fourteen. Boys usually trail behind by about two years—hence the comical sight of thirteen-year-old boys slow-dancing with thirteen-year-old girls a head taller.

Here’s what typically happens:

The hands and feet grow first, resulting in a frequently awkward appearance. Until the arms and legs catch up, teenagers may literally trip over their own feet. Next the thighs widen and boys’ shoulders and girls’ hips broaden. Then the trunk of the body lengthens. The bones in the face grow too—particularly the lower jaw—bringing about a noticeable transformation.

To help you appreciate the dramatic changes that take place, consider that every year since the age of two or three, your youngster has grown an average of two inches and gained about five pounds. During adolescence, however, you can expect that rate to double. A boy may sprout four inches in twelve months, and by the time this surge is complete he’s likely to have added thirteen to fourteen inches and forty pounds. Girls’ growth is significant too, cresting at three plus inches in the six to twelve months before they begin having menstrual periods. Growth slows considerably soon afterward. In all, they gain nearly ten inches and twenty-five pounds.

Once the peak period of development is over, you can trim the clothing budget, as most teens grow no more than another inch or two. Youngsters leave adolescence having attained nearly all of their adult height.

Puberty: Blame It On Hormones

Hormones, chemical messengers produced by the body’s glands, travel through the bloodstream to regulate specific cells and organs. They are central to growth, sexual characteristics, procreation, metabolism, personality traits and mood. Some parents would go so far as to say that hormones dictate their teenager’s every waking thought.

The initiating event of puberty is one you can’t see. For reasons that are not fully understood, sometime between the ages of seven and eleven in girls, and nine and a half to thirteen and a half in boys, the pituitary gland at the base of the brain releases two hormones that signal a girl’s ovaries and a boy’s testicles to begin producing the female sex hormone, estrogen, and the male sex hormone, testosterone, respectively.

Each sex hormone then instructs reproductive structures (the ovaries, uterus, fallopian tubes and vagina in girls; the testes, penis, vas deferens and epididymis in boys) to develop or mature in preparation for one day being able to bear or father children. Estrogen and testosterone also trigger the development of secondary sex characteristics, which encompass other male-female distinctions, such as women’s breasts and rounded hips, and men’s facial hair and muscle development. The growing ovaries and testicles secrete increasing amounts of sex hormones, further fostering the process of puberty.