Thyroid hormone system disrupting chemicals

Area of Science:

• Endocrinology
• Environmental Health
• Toxicology

Background:

• The thyroid hormone system is crucial for regulation, synthesis, distribution, metabolism, and action of thyroxine and its metabolites.
• Endocrine disruptor compounds (EDC) target the thyroid hormone system at multiple levels.
• Effects often occur at the pre-receptor level, influencing T3 ligand availability and thyroid hormone action.

Purpose of the Study:

• To review the impact of EDC on the thyroid hormone system.
• To highlight the mechanisms by which EDC exert adverse effects.
• To emphasize the risks to human and animal health and the environment.

Main Methods:

• Review of evidence from nutritional, pharmacological, and molecular genetic studies.
• Analysis of mechanistic studies in animal models.
• Examination of epidemiological data linking EDC exposure to thyroid dysfunction.

Main Results:

• EDC affect thyroid hormone feedback regulation, synthesis, distribution, metabolism, and action.
• Tissue-specific components like transporters, deiodinases, and receptors are key targets for EDC.
• Animal studies confirm cause-effect relationships, and human studies show risks to development and metabolism.

Conclusions:

• The thyroid hormone system is highly conserved and vulnerable to EDC across species.
• EDC exposure, particularly in iodine-deficient populations, poses significant risks to human health, development, and the environment.
• Adverse effects impact fetal/neonatal brain development, growth, differentiation, and adult metabolic processes.