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Puberty has been defined as the activation of the hypothalamic–pituitary–gonadal axis, which leads to gonadal maturation and the subsequent somatic manifestations associated with increased sex steroids and anabolic hormones. Adolescence refers to the development of adult social and cognitive behaviors. This is a period of intense physical and psychological changes. The sexual maturity rating (SMR) system described by Tanner and Marshall has been used to characterize the secondary sexual stages of puberty in boys based on pubic hair and genital development (PH1–5 and G1–5), and in girls based on breast and pubic hair development (B1–5 and PH1–5). Somatic changes observed during puberty correlate more closely with the SMR stage than with chronological age.


Nearly 20% of the final adult height is achieved during puberty. The growth rate in childhood averages 5 to 6 cm per year. Prior to puberty there is a slight deceleration in growth rate. Pubertal growth is triggered by the pulsatile secretion of gonadotropin-releasing hormone, which leads to the release of gonadotropins and in turn sex steroids, which facilitate accelerated growth hormone secretion. Typically, both males and females begin their pubertal growth spurt when they reach SMR stage 2. However, boys most often reach their peak height velocity (PHV) at a later stage of genital development (G4 and PH4) compared to girls in relation to breast development (B3; Table 65-1). Linear growth in girls slows after menarche with an average of 7 cm of height increase after menarche. Height increases are usually complete by a bone age of 15 years in girls. In most boys, linear growth is complete at a bone age of 17 years. The average PHV in boys is 9.5 cm/year, while in girls is 8.25 cm/year. Thus, the longer period of growth and a higher height velocity contribute to a greater adult height in males compared to females. Final adult height is largely determined by the genetic potential, reflected in the mid-parental height.


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