Sexual differentiation, maternal-fetal physiology, hormones and behavior

The focus of current research is on the effects of fetal exposure to low doses of natural estrogens and to estrogenic endocrine disrupting chemicals. In these studies doses are used that have been shown to be in the hormonally active range based on in vitro studies using intact cells in human serum. Pregnant mice are fed physiologically relevant rather than toxic doses of estrogenic chemicals, and effects on differentiating reproductive organs are examined for evidence of imprinting of selected genes involved in organogenesis. In addition, reproductive organ function and behavior in the offspring are examined during later life.

Results show that fetal exposure to low doses of natural and synthetic estrogenic chemicals (as much as 600,000-times lower than doses used in traditional toxicological studies) lead in males to a permanent increase in prostate size, changes in enzyme activity and steroid receptor numbers in a number of organs, a decrease in sperm production, and increased aggressiveness, while in females, changes in neuroendocrine and uterine function as well as behavior occur. These findings provide the first experimental evidence that exposure to environmentally relevant doses of man-made estrogenic chemicals found in plastics and pesticides during fetal life can irreversibly alter the course of fetal development.