Kids grow up so fast, but some seem to spring up overnight. Witness the trajectory of Malia Obama, the older daughter of President and Mrs. Obama, who at the age of 13 stands almost as tall as her mother. Estimates put her at 5-foot-9 or 5-foot-10, not that unusual for a child with tall parents, but definitely taller than most children her age.
No doubt she experienced a growth spurt, a natural occurrence that happens in puberty. This is the time when the body grows the fastest, says Dr. Jamie Wood, a pediatric endocrinologist at Children's Hospital Los Angeles, following a fairly steady growth rate in childhood.
For girls, Wood adds, this growing stage happens about two years after girls start developing breasts (average age 10) and about two years after boys have an increase in the size of their testicles (average age 12).
There's some variation in those ages, of course, Wood said, but that rapid growth period is tied to a rise in estrogen in girls and testosterone in boys. "They work synergistically with growth hormones to cause elongation in the long bones of the body," causing the spurt.