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Female serum concentrations (n = 456) of estradiol (E2) and estrone (E1) by age, stratified by Tanner breast stages B1–B5: B1, n = 178; B2, n = 71; B3, n = 69; B4, n = 95; and B5, n = 43. Number of adolescents postmenarche (filled circles), n = 112.
