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Adolescence comprises a period in the life cycle between childhood and adulthood. Biological, psychological, social, environmental, and legal changes influence the definitive onset and termination of adolescence. Pubescence is often described as the onset of adolescence; however, the mean age of onset of puberty in girls in the United States varies by race and is earlier than in previous generations. The mean age of onset for white girls is 9.7 years with a range of onset from 7.8 to 11.6 years; and for black girls, 8.1 years with a range of onset from 6.1 to 10.1 years. In boys, the onset of puberty has remained stable at 11.4 years of age with a range of 9.5 to 13.51-6 (see Chapter 540). For purposes of discussion in this section, adolescence in chronologic years is defined as the period from 10 to 21 years.

All bodily tissues are affected by the biological changes of puberty. Growth of the reproductive, cardiovascular, and musculoskeletal systems is closely correlated during this period. The major biological changes occurring during puberty can be classified into 6 groups: skeletal growth, alterations in body composition, cardiorespiratory changes, hematologic development, neuroendocrine development, and reproductive maturation. Chronologic age does not always correlate with biological maturity. Sexual maturation rating (SMR) stages, as originally described by Tanner and Marshall, provide a more accurate assessment of the biological developmental stage of the adolescent (see Chapter 540).7,8

The secondary growth spurt at pubescence accounts for approximately 25% of final adult height.9 As outlined in Table 63-1,10 the growth spurt for girls occurs at an earlier sexual maturity rating (SMR 2–3) than for boys (SMR 4). Girls reach a final mean adult height of 163.8 cm at a mean age of 16 years compared with 176.8 cm for boys at a mean age of 18 years. Assessment of skeletal growth during adolescence is done through the use of a height-velocity curve with consideration of the gender-specific sexual maturity rating. Bone age can be determined through the use of a hand roentgenogram.11

Table 63-1. Clinical Correlates of Pubertal Maturation

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