Endocrine or hormone systems are found in all mammals, birds, fish and other living organisms. In general, these endocrine systems are comprised of a gland that produces hormones and secretes them into general circulation or into spaces around the cells near the glands. Tissues all throughout the body have receptors that respond when the hormone binds its receptor. The effects of this binding are varied and are linked to the development, growth and the overall health of the organism. Although there are many different hormones present in the body, three very important hormones are estrogen, androgen, and thyroid.
As hormone signaling is crucial for proper development and growth of many organisms, chemicals or drugs that interrupt normal endocrine signaling and function can result in developmental defects, interference with reproductive processes, increase the risk for some types of cancer, and even alter the function of the immune and nervous systems. Chemical mediated endocrine disruption can occur when a compound mimics the endogenous hormone and activates the signaling pathway, resulting in over stimulation or false hormone may activate the signaling pathway at an inappropriate time. Disruption of normal endocrine signaling can also occur if a chemical binds to the endogenous hormone receptor and blocks the subsequent binding of the natural hormone.
Over the past several years there has been an increase in the number of studies linking exposure of humans, domestic animals, and other wildlife to endocrine-active chemicals, with adverse health effects. In domestic and wildlife species, adverse health effects have been associated with exposure to the following endocrine-active chemical groups:
Polychlorinated biphenyls and dioxins
Naturally occurring plant estrogens
Although environmental exposure to certain endocrine disruptive chemicals has been clearly linked to adverse effects in wildlife and domestic animals, the health effects to humans exposed to low environmental levels of these chemicals is less clear. In recent years there has been a decline in the quantity and quality of human sperm. There has been an increase in certain cancers, such as breast, prostate, and testicular. Because these cancers can have an endocrine basis for development it is possible that these trends may be due in part to a greater abundance and hence a greater exposure of humans to chemicals with endocrine activity.