The assessment for potential thyroid-mediated endocrine disruption in amphibians: Clarification on the use of new methods and on the interpretation of changes in thyroid histology.

Amphibians (specifically Xenopus laevis) are used as the model species to assess potential endocrine-disrupting properties in non-mammalian species through thyroid modality. The amphibian metamorphosis assay is the most frequently available test. Attempts have been made to modify this protocol in order to make it more fit for purpose and overcome potential limitations. In light of these developments, EFSA, with the support of the Working Group on Endocrine Disruptors, under the auspices of a self-task mandate here endeavours to clarify the pros and cons of newly proposed amphibian protocols when compared with the standard guideline tests. Moreover, recommendations to facilitate the interpretation of findings in relation to changes in thyroid histopathology have been included.