A limited number of reports of estrogen (E2) levels in prepubertal and early pubertal boys have been published because E2 assays have lacked adequate sensitivity. A new ultra-sensitive assay has permitted measurement of E2 levels in 23 normal boys progressing through puberty. Concentrations were measured at 4 month intervals over 5 - 8 years. As expected, the levels increased with stage of maturation in all. Table shows mean + SE. E2 levels correlated directly with chronological age, bone age, weight, height, pubertal stage, testosterone (T), and IGF-1 levels, but did not correlate with 24-h GH level. The level of T appeared to have the greatest influence on the E2 concentration. The time from peak growth velocity (GV) significantly correlated with E2. E2 had a positive correlation with GV prior to the time of peak GV, and a negative correlation after peak GV. The first significant increase in E2 by year relative to pubertal onset was 3 years after the onset of puberty. Peak E2 occurred 5 years after the onset of puberty. Peak GV occurred an average of 3 years after pubertal onset. In conclusion, E2 levels are very low in all boys before puberty and rise during puberty. E2 level is closely related to T concentration and to time of peak GV. These findings are consistent with the hypothesis that E2 at low levels influences skeletal growth and maturation in boys as well as girls, and with the hypothesis that continued exposure to E2 leads to epiphyseal fusion since there are significant data in the literature supporting the concept that E2 and not T is responsible for epiphyseal fusion. Further studies are required to separate the roles of E2, GH, and T, and other factors on growth and pubertal development.

Table 1
Full size table