The acceleration in the rate of growth in height that starts in late childhood and reaches a maximum (peak height velocity) during adolescence. Rate of growth in height decelerates after the peak and eventually ceases in late adolescence or young adulthood (see figure below). The growth spurt in girls is oestrogen induced, and begins coincidentally with (or just a few months before) the first signs of breasts (the second stage of breast development referred to as thelarche). Many girls have proportionally longer legs relative to the torso during the first year of puberty as growth of the legs (and feet) begins to accelerate first. Growth tends to reach a peak velocity, up to as much as 7-10 cm, midway between thelarche and menarche. With the onset of menarche, it starts to decline, and in the subsequent two years about another 5cm in height is attained. As with boys, this mainly involves growth of the trunk rather than the legs. For boys, growth accelerates more slowly and lasts longer. The outcome is a taller adult compared to females, with boys being on average about 10 cm more in height. Growth for boys begins to accelerate some 9 months after the first signs of testicular enlargement with the peak growth spurt occurring about 2 years after the onset of puberty, attaining a peak velocity of between 8 and 12 cm per year. In contrast to girls, the growth spurt is first evident in the feet and hands, then the limbs, and finally trunk. Adult height and epiphyseal closure are achieved at 17 to 18 years. The slower growth of boys is attributed to testosterone having less of an effect on bone growth and epiphyseal closure than estradiol.
