Hormonal studies and physical maturation in adolescent gynecomastia.

As part of a 3-year longitudinal study of lipid and hormonal changes during puberty, 536 boys aged 10 to 15 years were prospectively followed every 6 months to assess development of gynecomastia. The overall prevalence of gynecomastia in the 377 with complete data was 48.5% (51% of white subjects and 46% of black subjects). In the majority of subjects, gynecomastia developed during mid-puberty. Gynecomastia was bilateral in 55% of subjects, on the left side in 19%, and on the right in 26%. Gynecomastia was documented for only one visit in the majority of subjects. When subjects were matched at the onset of gynecomastia for race, visit number, and pubertal rating, there were no significant differences between those with or without gynecomastia in serum estradiol level, testosterone level, estrogen/testosterone, ratio, or dehydroepiandrosterone-sulfate level. However, free testosterone level, weight, and Quetelet index were all significantly lower, and the testosterone-estrogen binding globulin level was significantly greater, in those with gynecomastia. We conclude that approximately half of adolescent boys have transient gynecomastia, usually lasting less than 1 year; those with gynecomastia enter mid-puberty at an earlier age, have a lower Quetelet index, and have lower serum free testosterone levels.