The Science of Endocrine
Activity and Disruption
Through the efforts of governments, academia and industry, considerable progress has been made to develop scientific methods, tests and data that could distinguish between whether a substance is merely endocrine active, or whether, under certain exposure scenarios, a substance goes beyond a simple interaction and results in adverse health effects – these substances are often referred to as endocrine disruptors. A precise definition is important because the majority of the substances that may interact with the endocrine system result in effects that are harmless, or in some cases, even essential to our well-being.
Many substances and activities can be shown to impact the endocrine system – stress, food, and exercise are among the most common. What scientists care about most with regard to any substances known to cause endocrine activity, is whether that activity can lead to an adverse health effect. At doses and durations of exposure far higher than what we are ordinarily exposed to, we know that some substances can negatively impact the endocrine system and cause adverse health effects. At lower doses, those substances may not impact our health at all.
Science of the
The endocrine system naturally responds to exposure from our environment, both chemical and physical. For example, a change in temperature, food or daylight can affect the level of hormones circulating in our body.
How a chemical interacts with the endocrine system depends on a variety of factors, including the:
- Type and duration of the exposure to the chemical,
- Frequency of exposure,
- Potency of the chemical substance, and
- Ways in which the body absorbs and eliminates the substance.
The interplay of these factors can determine whether the endocrine system’s response to the chemicals is positive, neutral or negative.
Is it Positive? Neutral? Negative?
When our bodies are exposed to sunlight, the production of Vitamin D in the skin is stimulated, which helps with calcium absorption. The Vitamin D is ultimately converted into a hormone in the kidneys and liver that stimulates the intestines, bones and kidneys to activate calcium and phosphorus, thus resulting in normal bone development.
Plant-based soy phytoestrogens found in many foods have the potential to interact with the estrogen receptor. But scientific studies of large populations of healthy women have shown either no association between soy and breast cancer, or a protective association, meaning that women who consumed higher levels of soy had less breast cancer.
Steroidal estrogens (both naturally occurring estrogen and estrogen from synthetic contraceptive pills contained in human waste) have the potential to increase the frequency with which wild freshwater fish have altered sexual organs. Research in the United Kingdom has shown that when sewage discharge treatment has been insufficient to remove these estrogen contaminants, the reproductive tract of wild populations of male fish can be affected.