Polybrominated Diphenyl Ether (DE-71) Interferes With Thyroid Hormone Action Independent of Effects on Circulating Levels of Thyroid Hormone in Male Rats
Bibliographic record
Abstract
Polybrominated diphenyl ethers (PBDEs) are routinely found in human tissues including cord blood and breast milk. PBDEs may interfere with thyroid hormone (TH) during development, which could produce neurobehavioral deficits. An assumption in experimental and epidemiological studies is that PBDE effects on serum TH levels will reflect PBDE effects on TH action in tissues. To test whether this assumption is correct, we performed the following experiments. First, five concentrations of diphenyl ether (0-30 mg/kg) were fed daily to pregnant rats to postnatal day 21. PBDEs were measured in dam liver and heart to estimate internal dose. The results were compared with a separate study in which four concentrations of propylthiouracil (PTU; 0, 1, 2, and 3 ppm) was provided to pregnant rats in drinking water for the same duration as for diphenyl ether. PBDE exposure reduced serum T4 similar in magnitude to PTU, but serum TSH was not elevated by PBDE. PBDE treatment did not affect the expression of TH response genes in the liver or heart as did PTU treatment. PTU treatment reduced T4 in liver and heart, but PBDE treatment reduced T4 only in the heart. Tissue PBDEs were in the micrograms per gram lipid range, only slightly higher than observed in human fetal tissues. Thus, PBDE exposure reduces serum T4 but does not produce effects on tissues typical of low TH produced by PTU, demonstrating that the effects of chemical exposure on serum T4 levels may not always be a faithful proxy measure of chemical effects on the ability of thyroid hormone to regulate development and adult physiology.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".