Endocrine systems release hormones that act as chemical messengers.
The messengers interact with receptors in cells to trigger responses and prompt normal biological functions such as growth, embryonic development and reproduction. Scientists know that endocrine systems can be adversely affected by a wide variety of substances. A substance can interfere with the normal communication between the messenger and the receptor in the cell, so that the chemical message is not interpreted properly. Even very subtle effects on the endocrine system can result in changes in growth, development, reproduction or behaviour that can affect the organism itself, or the next generation. The specific mechanisms by which substances disrupt the endocrine systems are very complex, and not yet completely understood.