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Girls’ pubertal development occurred earlier than boys’
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Pubertal development may not be expressed solely with puberty onset and termination, as differential secondary sex characteristics occur at different stages and times depending on sex and ethnicity, according to new findings of a multisite, longitudinal study.
Researchers conducted the study to identify when adolescents were in sexual maturity stages II to V, explain the relationship between genital, breast and pubic hair development between age 9.5 and 15.5 years, and evaluate synchronized pubertal development across different characteristics.
For the Eunice Kennedy Shriver National Institute of Child Health and Human Development Study of the Early Child Care and Youth Development Network, researchers assessed breast development in 432 girls, genital development in 427 boys and pubic hair development in both sexes. Overall, 86.3% of girls and 85.2% of boys were white.
Children were followed from birth to age 15.5 years (1991 to 2006), and annual staging of secondary sex characteristics was performed between age 9.5 and 15.5 years (2000 to 2006).
Maturity stages
Girls were in breast maturity stages II and III earlier than comparable pubic hair stages (P<.001). However, girls completed breast and pubic hair development at about the same age.
Black girls had earlier breast and pubic hair development at all stages compared with white girls. Most white girls showed no evidence of breast (56.2%) or pubic hair (71.5%) development at age 9.5 years; black girls of the same age had some evidence of breast (69%) and pubic hair development (59.2%). At age 15.5 years, more than three-quarters of white girls were in sexual maturity stage V for breast (79.5% vs. 84.1%) and pubic hair (81.9% vs. 92.5%) development vs. black girls.
Conversely, boys arrived at stages II to V of genital development before pubic hair development (P<.001). However, pubic hair development was completed before genital development. Overall, it took boys about 4.5 years to go from stage II to stage V for genital development and 3.5 years for pubic hair development.
Black boys entered genital and pubic hair development about seven months before white boys. In addition, black and white boys completed genital development in about 4.5 years, but it took black boys about six months longer to complete pubic hair development.
At stage II, breast development preceded pubic hair development for 66.2% of girls. For 91.1% of boys, genital development preceded pubic hair development.
The researchers suggested replication of this study in a representative sample.
“The descriptive findings from this study are useful in understanding normative variation in the timing and change in secondary sexual characteristics at puberty,” the researchers said. “They will help identify children with atypical changes in sexual maturation and unusual progression of sexual maturation and growth disorders.”
Susman EJ. Arch Pediatr Adolesc Med. 2010;164:166-173.