Endocrine disruptors: can biological effects and environmental risks be predicted?

Area of Science:

• Environmental chemistry
• Endocrinology
• Toxicology

Background:

• Xenoestrogens are diverse nonsteroidal chemicals that interact with the estrogen receptor (ER).
• Most xenoestrogens exhibit significantly weaker activity compared to estradiol.
• Their interaction with the ER binding pocket is driven by structural similarities to estradiol, typically a phenolic A-ring.

Purpose of the Study:

• To explore the mechanisms of xenoestrogen activity and endocrine disruption.
• To evaluate the influence of ER binding on biological responses.
• To assess the consensus on low-dose effects and human risk from environmental xenoestrogen exposure.

Main Methods:

• Review of existing literature on xenoestrogen binding and activity.
• Analysis of factors influencing ER signaling pathway complexities.
• Examination of evidence regarding high-dose versus low-dose effects of nonsteroidal chemicals.

Main Results:

• Xenoestrogen activity is generally weak due to incomplete molecular fit within the ER binding pocket.
• ER binding alone has limited influence on endocrine disruption; response magnitude depends on the substance and pathway complexities.
• Factors like plasma binding, signaling pathway cross-talk, and androgen antagonism modulate xenoestrogen effects.

Conclusions:

• There is no consensus on whether low environmental levels of xenoestrogens pose a risk to humans.
• High doses of nonsteroidal chemicals can cause endocrine disruption, but low-dose effects are debated.
• Current screening programs for hormonally active chemicals may be premature due to the intricate mechanisms involved.