Assays to measure estrogen and androgen agonists and antagonists.

Substantial evidence has surfaced on the hormone-like effects of many xenobiotics in fish, wildlife and humans (Colborn et al., 1993). The endocrine and reproductive effects of xenobiotics are believed to be due to their 1) mimicking the effects of endogenous hormones such as estrogens and androgens, 2) antagonizing the effects of normal, endogenous hormones, 3) altering the pattern of synthesis and metabolism of natural hormones, and 4) modifying the hormone receptor levels. Estrogen mimics (xenoestrogens) are among the environmental chemicals found to cause reproductive impairment in wildlife and humans. All of these compounds were found to be estrogenic long after they had been released into the environment. A single causal agent can be identified in cases in which humans have had occupational exposures, whereas in cases where wildlife have shown signs of reproductive damage the exposure is usually a combination of endocrine disruptors that may have acted cumulatively. It has been hypothesized that environmental estrogens may play a role in the decrease of human semen quantity and quality of human semen during the last 50 years. They may also be partly responsible for the increased incidence of testicular cancer and cryptorchidism in males and breast cancer incidence in both females and males in the industrialized word. Testing this hypothesis will require: 1) the identification of xenoestrogens among the chemicals present in the environment, 2) the development of a methodology to assess the interactions among mixtures of xenoestrogens to which humans are exposed, and 3) the discovery of markers of estrogen exposure. The development of fast and sensitive bioassays is central to the achievement of these three goals.