Amphibian bioassays for thyroid disrupting chemical testing: Recent findings, methodological advances, and perspectives

Abstract

Thyroid disrupting chemicals (TDCs) pose significant risks to vertebrate development, yet current screening tests may not capture the diverse molecular targets and indirect mechanisms of TDCs. Amphibian metamorphosis, mediated by thyroid hormone signaling, has been recognized for many years as a robust in vivo model for detecting thyroid disruption. This review synthesizes the peer-reviewed literature published from January 2023 to July 2025 that assesses TDCs in amphibians. We evaluate recent findings from Xenopus test guidelines, methodological refinements, and emerging endpoints, including molecular, neurological, and hepatic biomarkers. We also highlight contributions from non-Xenopus amphibian species that improve ecological relevance. Finally, we discuss how these data can be integrated into modern toxicological frameworks such as new approach methodologies and adverse outcome pathways.