What is an Endocrine Disrupter?

Within the last decade the terms endocrine disrupter, endocrine modulator and hormone mimics have entered the lay and scientific jargon as terms to describe exogenous chemicals that alter the function(s) of the endocrine system and consequently cause adverse health effects in an organism, its progeny or subpopulations. However, these terms have been difficult to define, leading to different definitions in the literature, considerable controversy, and more importantly confusion within the scientific and lay communities about what is and what is not an endocrine disrupter. We therefore put forward the term endocrine toxicant as an alternative that may be more appropriate for several reasons.

For the term endocrine disrupter and its attendant definition to be useful it must allow us to separate chemicals into those that cause changes in hormone function and those that do not. This definition hinges on two key points: altered endocrine homeostasis and induction of an adverse health effect.

The endocrine system is a communication system that maintains normal physiological balance across multiple organ systems. It accomplishes this by modulating or regulating the activity of almost every body system in reaction to variations in body temperature, activity level, stress, and circulating levels of nutrients and hormones required for growth, reproduction, and metabolism. Hence, any exogenous chemical, no matter how innocuous, may disrupt the physiological balance of the body either by direct interaction with hormone receptors or indirectly through changes induced in other organ systems. For example, consuming food causes changes in numerous hormones involved in digestion and metabolism. It is also recognized that bright light will alter hormone levels in the brain affecting human behavior and depression. Thus, even foods and light could be considered as endocrine disrupters since they do induce functional changes in hormone levels. Hence, use of the terms disrupter, modulator or mimic does little to help us distinguish between chemicals that do or do not adversely alter endocrine homeostasis.

In screening chemicals for potential adverse health effects, some argue that it should be enough to show that exposure to a chemical alters the endocrine system to a measurable degree because even slight alterations in endocrine balance may be sufficient to induce adverse health effects in sensitive populations. While this is an important issue, it is not unique to chemicals that cause endocrine toxicity. Many toxicants, depending on level of exposure, will induce measurable changes in gene expression and in some cases circulating hormone levels that are within normal limits. Therefore, coupling the affected system (endocrine) with an adverse health effect will help discriminate between hazardous and non-hazardous endocrine disrupters - we suggest this is best accomplished by the term endocrine toxicant.

The term endocrine disrupter is widely used at present by representatives from the media, regulatory groups, academic scientists, and non-governmental organizations to communicate divergent meanings. The net result is significant confusion surrounding the messages that are being communicated concerning the potential for chemicals to interact with physiological systems and to induce endocrine toxicity. We therefore prefer the use of the term endocrine toxicants to describe chemicals that disrupt endocrine homeostasis and induce adverse health effects. This term clearly communicates that a chemical has been shown to be toxic through an endocrine mechanism and thus enables us to discriminate between chemicals with this property and those without.

Towards Less Confusing Terminology in Endocrine Disrupter Research. Working Paper. Agzarian, J., and Foster, W. (2005)