Possible effects of endocrine disruptors on male reproductive function

Endocrine disruptors act to alter blood hormone levels or the subsequent action of hormones, including effects on hormone production, release, transport, metabolism and/or elimination together with effects on cognate receptor binding and/or subsequent intracellular receptor actions. Confirmed alterations in reproductive development in wildlife species together with reports touting an increase in the incidence of human male reproductive tract abnormalities and decreased adult sperm counts in some parts of the world have increased public concern with endocrine disruptors. A biological plausible hypothesis has suggested that man-made chemicals act as endocrine disruptors resulting in altered development of the reproductive tract causing the observed effects. Based on current knowledge, the impact of endocrine disruptors on the male reproductive function remains to be appreciated. Epidemiological human studies are necessary to fill in the gap in our knowledge. Disturbances of hormonal regulation during fetal or postnatal development in humans may induce adverse effects on the male reproductive system, but these adverse effects of endocrine disruptors on humans are subtle, and difficult to research and detect. We have investigated fetal exposure to endocrine disruptors in Japan by analyzing umbilical cords, and changes of testis-weight in Japanese men by using analytical data of necropsy. This mini-review summarizes current endocrine disruptor issues on possible effects of endocrine disruptors on male reproductive function and the results of our recent research.