Endocrine Abstracts

Exposure to soy isoflavones (ISO), abundant in soy protein infant formula, during early postnatal life has benefits to bone health in female mice. Moreover, exposure during the first 10 or 21 days of life has been shown to interfere with structural development of female reproductive organs and results in heavier body weight. The study objective was to compare if shorter exposure to ISO, during the first 5 vs 10 days of life, results in lesser adverse effects on ovarian and uterine structure in adult mice. At birth, female pups (8–12 pups/l) were cross-fostered and litters were randomized to corn oil or ISO (7 mg/kg of body wt/day) treatment for the first 5 or 10 days of life. The 5-day protocol was selected to mimic previously published studies investigating the effects of environmental estrogens (i.e. diethylstilbestrol) on reproductive and skeletal development. Body and organ weights, and histology of ovaries and uterus were analyzed. There were no differences in the ovary or uterus weight, number of ovarian follicles, number of multiple oocyte follicle or percent of ovarian cysts with 5 or 10 day ISO intervention compared to respective controls. Ten day ISO group had higher body weight from 6 days to 4 months of age and higher percent of ovarian hyperplasia than their respective control. Lower number of ovarian corpus luteum and a higher incidence of abnormal changes were reported in the uteri of both ISO groups compared to their respective control. In conclusion, 5 and 10-day exposure to ISO had similar long-lasting adverse effects on the structure of ovaries and uterus in adult mice, identifying the first five days of life as a susceptible window for programming reproductive development. Only the 10-day ISO exposure resulted in greater body weight gain at adulthood.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.