Effects of maternal exposure to diethylstilbestrol on the development of the reproductive system and thyroid function in male and female rat offspring.

Diethylstilbestrol (DES) was administered subcutaneously at 1.5 or 15 microg/kg/day (DES 1.5 group, DES 15 group) to pregnant SD rats daily on days 7-21 of gestation to investigate its effects on the development and functions of the reproductive system and thyroid gland in their offspring. Of the 11 pregnant rats in the DES 15 group, only one delivered a live pup. Rat pups in the DES 1.5 group were autopsied at 1, 3, or 6 weeks after birth. In the DES 1.5 group, the plasma T4 concentrations at all weeks of age at autopsy were significantly increased, the TSH concentration at 6 weeks of age was also significantly increased, and the height of thyroid follicular epithelial cells was increased at 3 weeks. The testosterone concentration in the DES 1.5 group at 6 weeks was significantly decreased and the plasma LH concentration was increased. The DES treatment increased the plasma FSH concentration in female pups at 3 weeks, increased the percentages of primary and secondary ovarian follicles, and decreased the percentage of primordial follicles, but did not influence the timing of the vaginal opening or the onset of the estrous cycle. These observations indicate that prenatally administered DES increases thyroid function, and has an inhibitory effect on testicular function and a promoting effect on female reproductive function.