Environmental Toxicology and Endocrine Disrupting Chemicals

Chemicals of natural and manmade origins such as phytoestrogens, pesticides, and industrial waste have been shown to disrupt hormone signaling or the endocrine system of many species. Substances known to disrupt endocrine function are collectively classified as endocrine disrupting chemicals (EDCs). Hormones typically work through a receptor, which is a protein found in the cells of tissues regulated by that hormone. For example, estrogen, which in part regulates the reproductive cycle, is detected by estrogen receptors in the reproductive tract tissues of females. Many EDCs have been shown to bind to hormone receptors and effectively mimic or block the action of natural hormones. The disruption of normal hormone signaling may reduce the reproductive success of some endangered species, including rhinos, polar bears, and crocodilians.

The purpose of the San Diego Zoo's Reproductive Physiology Division's research is to develop a system of screening EDCs for their capacity to interact with hormone receptors of endangered species whose successful reproduction might be compromised by exposure to these chemicals. Using recent advances in biotechnology, researchers are able to screen chemicals for endocrine disrupting properties without exposing animals to potentially harmful substances. This information can be used to identify chemicals in the environment that might be a threat to endangered species and assist regulatory agencies with policy decisions regarding acceptable levels of environmental exposure.