Genistein impairs early testosterone production in fetal mouse testis via estrogen receptor alpha

► Genistein, an isoflavone found in soy products, mimics the actions of estrogens. ► The fetal testis is responsive to estrogens. ► Genistein inhibits testosterone secretion during early fetal development. ► This effect occurs through an ERα-dependent mechanism. ► It starts at 10 nM genistein, a concentration compatible with human consumption.