Abstract: ObjectiveTo study the effects of soy isoflavones(SIFs)on ovarian development of immature mouse and to provide experiment data for research of female development toxicity.MethodsForty eight postnatal day(PND)21 ICR mice were divided randomly into control,low-,medium-,and high-dose SIFs groups.The mice were treated with SIFs at the concentration of 50,100 and 200 mg/kg.bw,respectively,by gavage once a day for 5 weeks.After the treatment,serum sex hormone,the day of vagina opening,ovarian coefficient,and constituent ratio of different stage follicles were determined.ResultsThe ovarian coefficient of the high-dose SIFs group(0.436±0.120 mg/g)was lower than that of the control group(0.987±0.420 mg/g)(P<0.05).The serum 17p-estradiol(E2)level of the high-dose SIFs group(32.96±12.83 pg/ml)was lower than that of the control group(53.76±16.44 pg/ml)(P<0.05).There were no significant differences in serum progesterone(P4)among all the groups.Compared with control group(33.50±2.68 days),the age of vagina opening in the medium-dose group was accelerated(31.14±1.21 days),with a significant difference(P<0.05).With the increasing dose of SIFs,the constituent ratio of mature follicles decreased and that of atretic follicles increased,with significant difference between high-dose SIFs group and the control group(P<0.05).ConclusionSoy isoflavones treatment from weaning to sexual maturity could affect ovary development in mice.