Additional evidence against the ethanol – estrogen secretion mechanism comes from studies of postmenopausal women using HRT. While women in the Dorgan study were not using HRT, other studies have shown that alcohol does increase estrogen levels in postmenopausal women who are taking HRT(Ginsburg et al., 1996). Therefore, if the effect of moderate alcohol on breast cancer risk were due to increased estrogen levels, and alcohol only increases estrogen levels in postmenopausal women on HRT, it follows that the relationship between moderate alcohol consumption and breast cancer risk would only be observed in postmenopausal women on HRT. However, in the Allen study, the increased breast cancer risk per 10 g/day in current users of HRT was no different than in non-users. Similarly, Li et al. (2010) found that the multivariable adjusted risks of hormone receptor positive ductal cancers per drink per day among current HRT users were similar to those for never users.
