Limitations to the use of secondary sex characteristics for gender comparisons.

Background: To control for the confounding effect of maturation many researchers use secondary sex characteristics to compare individuals within and between genders. However, this assumption presumes that the timing and tempo of secondary sex characteristics is identical in both genders.

Aim: The study investigated the timing and relationships between sexual and somatic maturation indices between and within genders.

Subjects And Methods: Eighty three boys and 75 girls, aged between 8 and 15 years at study entry, were measured every 6 months for 6 consecutive years. Sexual maturation was assessed through pubic hair, facial hair and axillary hair development in boys, and pubic hair development and menarcheal status in girls. Somatic maturation was assessed through age at peak height velocity (PHV).

Results: Low to moderate correlations (r = 0.30-0.55, p < 0.05) existed between age of PHV and age of reaching each pubic hair stage. The majority of boys reached PHV in pubic hair stage 4 (79.2%). The majority of girls reached PHV in pubic hair stage 3 (42.5%) and pubic hair stage 4 (47.5%).

Conclusion: Boys and girls differ in the timing and tempo of somatic and sexual maturity. Thus boys and girls should not be aligned on secondary sex characteristics when controlling for the confounding effects of maturity.