Fig. 2. Graphical overview of the potential effects of genistein in specific tissues via modulation of estrogen synthesis and metabolism. Upon soy-rich food or supplement intake, genistein might reach sufficient levels to decrease estrogen (E) levels in healthy breast tissue due to the inhibition of aromatase, but increase the activity of breast cancer-associated aromatase. Genistein may affect ovarian and endometrial functions by the inhibition of 17β-HSD, SULT1E1 and CYP1B1 activity, leading to increased intracellular E levels and lower circulating levels of estrogen sulfates (ES). In premenstrual women, genistein suppresses circulating LH and/or FSH concentrations.186,187 A = androgen; DHEA(S) = dehydroepiandosterone (sulfate); E = estrogen; FSH = follicle stimulating hormone; LH = luteinizing hormone.