Because the range of normal onset and progression of puberty is broad and is different in boys and girls, pediatricians must have a solid grasp of normal pubertal events to assess when a child falls outside the normal range and needs evaluation or treatment.

Puberty is initiated by changes in the sensitive negative feedback system that exists among the gonads, hypothalamus, and pituitary in the prepubertal child. Puberty involves an increase in gonadal steroid production (i.e., gonadarche) and an increase in adrenal steroid production (i.e., adrenarche).

In most girls, puberty begins between 8 and 13 years of age and is completed, on average, in 4.2 years (range, 1.5 to 6.0 years). In 90% of girls, breast development (thelarche) is the first sign of puberty. The time from onset of breast buds to menarche is 2.3±1.0 years.

A 1997 cross-sectional study conducted by Herman-Giddens et al. showed that a substantial portion of girls have pubertal changes at age 7 years. The changes occurred earlier in black than in white girls. In 2002, Wu et al. reported data from the Third National Health and Nutrition Examination Survey (NHANES III), conducted between 1988 and 1994, showing that, on average, black girls enter puberty first, followed by Mexican American and then white girls. Including current body mass index (BMI) did not modify the relationship between race/ethnicity and pubertal status, with the exception of attainment of menarche. Higher BMI led to earlier age at the onset of menarche. Sun et al. also reported data from NHANES III in 2002 finding little statistical difference between sexual development in non-Hispanic white girls and Mexican American girls. Using NHANES III, Sun et al. and Wu et al. both found the median age for onset of breast development was 9.48, 10.38, and 9.80 in non-Hispanic black girls, non-Hispanic white girls, and Mexican American girls, respectively. Similarly, the median age for onset of pubic hair in girls was 9.5, 10.5, and 10.3, respectively.

Chumlea et al. used NHANES III data in 2003 to show that the median age for attainment of menarche is 12.43 years, which is not significantly different from that reported for U.S. girls in 1973. Again, non-Hispanic black girls had a significantly earlier age of onset of menarche than did non-Hispanic white and Mexican American girls (12.06 years, 12.55 years, and 12.25 years, respectively).

In the vast majority of boys, puberty begins between 9 and 14 years of age and is completed, on average, in 3.5 years (range 2.0 to 4.5 years). In most boys, testicular enlargement (length greater than 2.5 cm) is the first sign of puberty. Sun et al. reported data from NHANES III showing the median age of genital development in boys to be 9.2 years, 10 years, and 10.3 years for non-Hispanic black boys, non-Hispanic white boys, and Mexican-American boys, respectively.

Classically, if a girl shows signs of pubertal maturation before she is 8 years of age or a boy shows signs of puberty before he is 9 years of age, the child should be evaluated for precocious puberty. The 1997 data by Herman-Giddens et al. were interpreted as lowering the age for evaluation to 6 years for black girls and 7 years for white girls. These recommendations are controversial, although detailed etiologic evaluations in 6to 8-year-old girls usually are not revealing of pathology. Each child must be considered individually, including past medical history, tempo of puberty, and physical examination. Conversely, if no signs of pubertal development occur by 13 years of age in girls or by 14 years of age in boys, the child should be evaluated for pubertal delay. Timing and progression of puberty is important. Pubertal changes that progress too rapidly or arrest in progression require evaluation.