Blood concentrations of estradiol and sex hormone-binding globulin in relation to age at menarche in premenopausal British and Japanese women.

In a cross-sectional study, serum estradiol (E2) and sex hormone-binding globulin (SHBG) concentrations were not significantly related to age at menarche in premenopausal British women in the luteal or follicular phases of the cycle. In Japanese subjects in the luteal phase, a marginally higher concentration of E2 was observed in those who had undergone an early rather than a late menarche. In British women, previous oral contraceptive users had significantly lower luteal phase E2 concentrations than never users.