Revised Guidance Document 150 on Standardised Test Guidelines for Evaluating Chemicals for Endocrine Disruption
This guidance document was originally published in 2012 and updated in 2018 to reflect new and updated OECD test guidelines, as well as reflect on scientific advances in the use of test methods and assessment of the endocrine activity of chemicals. The document is intended to provide guidance for evaluating chemical using standardised test guidelines. Specific objectives include providing a description of the OECD conceptual framework for evaluating chemicals for endocrine disruption, background on the standardised test methods used, and guidance for interpreting the outcome of individual tests. The general approach taken by the document is primarily to provide guidance on how test results might be interpreted based on the outcome of standardised assays. Key questions addressed in the document concern likely mechanisms of endocrine action and any resulting apical effects that can be attributed to such action. The document is not proscriptive but provides suggestions for possible next steps in testing (if any) which might be appropriate for a regulatory authority to take, given the various data scenarios. The guidance document is focused primarily on endocrine modalities included in the conceptual framework; estrogen, androgen, and thyroid mediated endocrine disruption and chemicals that interfer with steroidogenesis.
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Uterotrophic Bioassay in Rodents (UT assay) (OECD TG 440) (including OECD GD 71 on the procedure to test for anti-estrogenicity)
TG 440 is an OECD validated in vivo short-term screening test based on the increase in uterine weight or uterotrophic response. The Uterotrophic Bioassay relies for its sensitivity on an animal test system in which the hypothalamic-pituitary-ovarian axis is not functional. Two oestrogen sensitive states in the female rodent meet this requirement: i) immature females after weaning and prior to puberty and ii) young adult females after ovariectomy with adequate time for uterine tissues to regress. The test substance is administered daily by oral gavage or subcutaneous injection. Each treated and control group should include at least 6 animals. Graduated test substance doses are administered to a minimum of two treatment groups of experimental animals using one dose level per group and an administration period of three consecutive days for immature method and a minimum administration period of three consecutive days for ovx-adult method. The animals are necropsied approximately 24 hours after the last dose. For oestrogen agonists, the mean uterine weight of the treated animal groups relative to the vehicle group is assessed for a statistically significant increase. A statistically significant increase in the mean uterine weight of a test group indicates a positive response in this bioassay. The report should include: the daily body weights, the daily record of status of animal, the wet and blotted uterine weight, the daily food consumption.
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