Endocrine hormones act as control agents that regulate homeostasis, development and many other bodily functions. They are secreted directly into the blood by the endocrine glands (pineal, hypothalamus, pituitary, thyroid, parathyroids, thymus, adrenals, pancreas, and ovaries or testes). The disruption of the endocrine system by chemicals, both natural and synthetic, in both experimental systems and humans is an area of toxicology that has received focused international attention since 1991 and is highly relevant to the American Chemical Society (ACS).
Endocrine disruption is the alteration of the endocrine system that causes adverse health effects in an intact organism, or its progeny, or (sub) populations. Endocrine hormones naturally act at ultra-low concentrations and certain chemicals are suspected of altering endocrine function at similarly low concentrations, which sometimes occur in the environment. A large and growing body of environmental health literature shows that endocrine-disrupting substances have complicated dose-response curves that do not fit the central tenet of regulatory toxicology, namely, that the ‘dose makes the poison.’ Like the hormones whose actions they disrupt, endocrine-disrupting chemicals can follow what endocrinologists call bi-phasic, or non-monotonic, dose response curves. This makes it impossible to predict the effects of low-dose exposures based upon high-dose experiments. The effects can be not only different, but opposite. While well established in medical endocrinology, such responses have been less well understood in traditional toxicology.
The American Chemical Society strongly endorses expanded endocrine disruptor education and research and the development of more effective science-based, decision-making tools and methods for reducing and eliminating exposures of humans and the environment. Specifically, ACS encourages expansion of funding for the following:
- in vitro and in vivo laboratory studies and human epidemiological investigations;
- mechanisms of action with emphasis on understanding non-monotonic dose-response behaviors;
- improvement of early identification of endocrine active chemicals and chemical classes;
- identification of exposure pathways, uptake mechanisms, and trends in human exposures and impacts; and
- design of epidemiological research to reflect biological mechanisms.