Height and Growth Rate Plotting height increments (i.e., growth velocity) against the phases of puberty allows one to see relationships during puberty (Fig. 29.2). Girls reach peak height velocity early in puberty before menarche. As a consequence, they have limited growth potential after menarche. In contrast, boys reach peak height velocity about 2 years later than girls. Boys grow an average of 28 cm during the growth spurt, in comparison to a mean of 25 cm for girls. Adult men eventually are an average of 13 cm taller than adult women because they are taller at the onset of the growth spurt. Hormonal control of the pubertal growth spurt is complex. Growth hormone (GH), insulinlike growth factor 1 (IGF-1), and gonadal steroids play major roles. Adrenal androgens appear to be less important. Mutations limiting conversion of androgens to estrogens in males confirmed that estrogen is the major stimulus to the pubertal growth spurt in both boys and girls (11).
During the growth spurt associated with puberty, the long bones in the body lengthen and the epiphyses ultimately close. The bone or skeletal age of any individual can be estimated closely by comparing x-rays documenting the development of bones in the nondominant hand (most commonly), knee, or elbow to standards of maturation for the normal population. The Greulich and Pyle atlas is used most often for this purpose (12). Skeletal age is more closely correlated with pubertal stage than with chronologic age during puberty. With height and chronologic age, an individual’s bone age can be used to predict final adult height using the Bayley-Pinneau tables (13). Bone age determinations can be used to assess the degree of delay, monitor subsequent development, and estimate final adult height.
Figure 29.4 Diagrammatic depiction of Tanner pubic hair staging in adolescent women. (From Ross GT, VandeWiele RL, Frantz AG. The ovaries and the breasts. In: Williams RH, ed. Textbook of endocrinology. 6th ed. Philadelphia, PA: WB Saunders, 1981:355, with permission; adapted from Marshall WA, Tanner JM. Variations in patterns of pubertal changes in girls. Arch Dis Child 1969;44:291–303.)
Another practical clinical approach to predicting adult height uses midparental height. The adjusted midparental height is calculated by adding 13 cm to the mother’s height (for boys) or subtracting 13 cm from the father’s height (for girls) and then determining the mean of the heights of the parents, including the adjusted height of the opposite-sex parent. Adding and subtracting 8.5 cm to the calculated predicted height approximates the target range of the 3rd to the 97th percentile for the anticipated adult height of the child. This quick calculation can be of assistance in evaluating individuals with delayed or precocious pubertal development and those with short stature.
Several changes in body composition occur during pubertal development. Although lean body mass, skeletal mass, and body fat are equal in prepubertal boys and girls, by maturity, men have 1.5 times the lean body mass and almost 1.5 times the skeletal mass of women, whereas women have twice as much body fat as men (1). The changes in body contour in girls, with accumulation of fat at the thighs, hips, and buttocks, occur during the pubertal growth spurt. In this regard, testosterone is a potent anabolic steroid and is responsible for the major changes in boys, whereas estrogen increases total body fat in a characteristic distribution at the thighs, buttocks, and abdomen in girls.