Effect of exposure to high isoflavone-containing diets on prenatal and postnatal offspring mice.

Isoflavone (IF), a type of phytoestrogen, has multiple beneficial effects, but too much phytoestrogen can have adverse effects on offspring. To examine whether chronic exposure to high IF has adverse effects on reproductive development, mice offspring were exposed to IF through dietary administration to dams during pregnancy and lactation and to the offspring directly after weaning until sacrifice. In male offspring, there was no difference between the IF group and controls; however, in female offspring in the IF group, remarkably earlier puberty and induction of multioocyte follicles on postnatal day (PND) 21 were observed. Gene expression levels of estrogen receptor beta decreased in the ovary and vagina on PND 21. These results suggest that chronic exposure to higher than normal levels of IF induces alterations in the reproductive development of female mice through an estrogenic effect.