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Thyroid disruption – publication of workshop report

The final report detailing the scientific workshop held to discuss issues related to the interpretation of thyroid disruption outcomes held in spring 2017 has been published by the European Commission. As part of this project, case studies were reviewed with the intention of elucidating several aspects and issues highlighted as important for understanding thyroid disruption. The topics discussed were:


  • the rat as predictor of human effects;
  • the relevance of compensatory effects in protecting against thyroid disruption;
  • the role of hepatic metabolism in thyroid insufficiency;
  • better measures of downstream effects of thyroid disrupting chemicals;
  • the relevance of thyroid tumours that arise via thyroid hormones;
  • thyroid systems across taxa, to discuss the relevance of mammalian data in environmental assessments and of non-mammalian data in human health assessment were explored.

A strategy for developing improved or novel endpoints important for detecting thyroid disruption could unfold at the following levels:

  • thyroid histology improvements;
  • extension of the timing of exposure, emphasising developmentally exposed animals;
  • the set of downstream effects should include brain morphology, especially the developing brain.

The workshop concluded that until these gaps are filled, it is necessary to evaluate substances on the basis of incomplete data regarding thyroid disruption. In this context, the finding of diminished serum thyroid hormone concentrations in animal studies should be taken as predictive of adverse effects in humans in the absence of substance-specific data.

It was noted that observations of thyroid disruption in rodent laboratory studies can be useful for the identification of thyroid disrupting properties in other wildlife mammalian species. Considering the preservation of the thyroid system across taxa, such data would also raise concerns for e.g. birds, fish or amphibians, although species-species extrapolations will not be straight-forward due to differences in exposure routes and other factors (e.g. the presence of a placenta in mammals).

The report can be found here:(

The outcome and conclusion of this workshop are likely to be included in updated EFSA guidance on endocrine disruption.

For advice on risk assessment and further information on the registration of plant protection products, biocides or general chemicals, or any other regulatory issues, please contact JSC on +44 (0)1423 520245,

Published 9th November 2017
Categories Agrochemicals, Links, News
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