Skeletal and Sexual Maturation in Japanese Children

Abstract

Japanese children appear to grow and mature faster than Caucasian children. To investigate such ethnic differences, we studied 2 cohorts of children in the Tokyo metropolitan area. Skeletal maturation (Greulich-Pyle method) and secondary sex characteristics (Tanner's criteria) were assessed in 731 boys and 573 girls aged 1-19 years who attended for minor illnesses between 1985 and 1991. The menarchial age (“status quo”method) was assessed in 2234 girls aged 9-18 years who were enrolled in a private school in 1989.The mean bone age exceeded chrononological age by at least 1 year in pubertal children of both sexes. The first sign of puberty was testicular growth (≥ 3ml) in boys, being attained at a mean age of 10.8 years, and breast development (Tanner stage 2) in girls, at a mean age of 10.0 years. The mean age for Tanner stage 4 pubic hair development was 14.9 years for boys and 13.9 years for girls, respectively. The mean menarchial age was 12.25 years with a standard deviation of 1.25 years.The results indicate that skeletal and sexual maturation is approximately 1 year earlier in Japanese compared to Caucasians, though pubic hair development is significantly slower in Japanese. The difference in the overall pattern of skeletal and sexual maturation between Japanese and Caucasians calls for specific Japanese standards for bone age and sexual maturation stages.