Daily 17-β-estradiol exposure in non OC-users compared to daily ethinyl estradiol exposure, observed over 28 days measured in nmol/l. Open circles are endogenous E2 daily exposure, solid circles are unstandardized exogenous EE daily exposure and solid squares are exogenous EE exposure standardized by the RBA of EE to the estrogen receptor, which is 190. EE exposure is reported for each of seven OC formulations detailed in Table 1