Toward an AOP Network-Based Tiered Testing Strategy for the Assessment of Thyroid Hormone Disruption

Area of Science:

• Environmental toxicology
• Endocrinology
• Ecotoxicology

Background:

• Environmental pollutants pose risks to the thyroid hormone system.
• Current tools for assessing thyroid hormone disrupting chemicals are insufficient.
• Gaps exist in hazard and risk assessment methodologies for these chemicals.

Purpose of the Study:

• To demonstrate the utility of the Adverse Outcome Pathway (AOP) framework for thyroid disruption assessment.
• To address challenges in current fish testing protocols for endocrine disruptors.
• To propose a tiered screening and testing approach for thyroid hormone disruption.

Main Methods:

• Utilized the AOP framework and data generation strategies.
• Applied a suite of assays targeting key biological pathways.
• Implemented a tiered screening and testing approach.
• Guided by the OECD's Conceptual Framework for Endocrine Disrupting Chemicals.

Main Results:

• The AOP framework, combined with new data, can address testing challenges.
• A tiered approach using specific assays is feasible for thyroid disruption screening.
• The proposed methods are applicable to fish early life stage and general fish tests.

Conclusions:

• The AOP framework offers a viable strategy for assessing thyroid hormone disruptors.
• Integrated testing strategies improve the identification and assessment of these chemicals.
• This approach enhances the evaluation of environmental risks to thyroid hormone systems.