In recent years, some scientists have proposed that chemicals might inadvertently be disrupting the endocrine system of humans and wildlife. These chemicals are mostly man-made, found in many everyday products including plastic bottles, metal food cans, detergents, flame retardants, foods, food, toys, cosmetics and pesticides. Human exposure to these products occurs via ingestion of food, dust and water, via inhalation of gases and particles in the air, and through the skin.
Disruption of the endocrine system can occur in various ways. Some chemicals mimic a natural hormone, fooling the body into over-responding to the stimulus (e.g., a growth hormone that results in increased muscle mass), or responding at inappropriate times (e.g., producing insulin when it is not needed). Other endocrine disruptors block the effects of a hormone from certain receptors (e.g. growth hormones required for normal development). Still others directly stimulate or inhibit the endocrine system and cause overproduction or underproduction of hormones (e.g. an over or underactive thyroid). Certain drugs are used to intentionally cause some of these effects, such as birth control pills. In many situations involving environmental chemicals, however, an endocrine effect is not desirable.
Research shows that endocrine disruptors may pose the greatest risk during prenatal and early postnatal development when organ and neural systems are forming. Pregnant women and nursing mothers should be especially careful, as should both men and women thinking of having a baby.