There is contradictory data about the consequences of isoflavone (ISO) exposure during development of female organisms. Potential impacts on tumor risk, reproduction but also altered susceptibility to develop metabolic diseases like obesity or diabetes are discussed. The aim of this study was to investigate in depth how ISO exposure during adolescence modulates the estrogen sensitivity of the uterus, vagina and visceral body fat.

There is contradictory data about the consequences of isoflavone (ISO) exposure during development of male and female organisms. Potential impacts on tumor risk, reproduction but also altered susceptibility for metabolic diseases like obesity or diabetes are discussed. An important finding in studies with females was that estrogen sensitivity evidently is affected by lifelong ISO intake. The aim of this study was to investigate whether ISOs also impact on androgen responsiveness in males. Hence we conducted a dose response experiment in male rats starting exposure in utero, maintaining it through adolescence into adulthood. Until sacrification at PND 96 rats received a diet enriched with an ISO extract in different concentrations [IDD (ISO depleted diet); IRD50 (ISO rich diet; 50 mg ISO/kg food); IRD400 (400 mg ISO/kg food)].

The effects of isoflavones (ISO) on the female breast are controversially discussed. There is evidence that ISO-rich Asian diet decreases the incidence of hormone related cancer and postmenopausal disorders. Whether chronic exposure to ISO over all critical periods of mammary gland development modulates its estrogen sensitivity was tested in a dose-dependent animal study. From in utero stages, through weaning and adolescence into adulthood female Wistar rats were exposed to different diets enriched with varying concentrations of the soy extract Novasoy650®: ISO-depleted diet (IDD), IRD50 (50 mg ISO/kg diet) and IRD400 (400 mg ISO/kg diet). Rats were ovariectomized (OVX) at day 80 and treated with 4 µg/kg BW E2 or vehicle for 3 days after 2 weeks of hormonal decline. Intact animals served as control. In a second trial adult female rats were exposed to IRD400 directly after OVX for 2 weeks and then treated with E2 as described above.