Association of Bisphenol Exposure and Serum Hypothalamic–Pituitary–Thyroid Axis Hormone Levels in Adults and Pregnant Women: A Systematic Review and Meta-Analysis
Bibliographic record
Abstract
Background: Bisphenols (BPs) are present in medical instruments, plastic containers, and personal care products (PCPs). Bisphenol A has been replaced by its alternatives, bisphenol S, F, AF, and B. Due to the awareness of their toxicity, mixed exposure to these alternatives at the regional level has been given less attention; there is a need to study this area of research. This meta-analysis examined the exposure of urinary bisphenol A and its metabolites to blood Hypothalamic–Pituitary–Thyroid axis hormones (HPT axis hormones) in pregnant women and adult males and females. We searched Embase, PubMed, Web of Science, Cochrane Library, and CINAHL until 8 January 2025, yielding 4588 articles using the PECO framework. Quality assessment was done using AHRQ: Agency for Healthcare Research and Quality for cross-sectional and NOS: Newcastle Ottawa Scale for cohort studies, with combined exposure evaluated using random and fixed-effect models. The I2 test assessed heterogeneity. We included eighteen studies for the final analysis. Fixed-effect model estimates revealed that BPA is negatively associated with thyroid-stimulating hormone (TSH) in female and male adults (β = −0.02; 95% CI = −0.04 to −0.01); (β = −0.08; 95% CI = −0.14 to −0.02). In Females, BPA was positively associated with free thyroxine, FT4 (β = 0.001, 95% CI, 0.001 to 0.001). In the male group, BPA was negatively associated with FT4 (β = −0.001, 95% CI, −0.001 to −0.001). As per pregnant women, there was no association found between exposure to bisphenols and total Thyroxine (TT4), FT4, and TSH in both trimesters (β = 0.010, 95% CI = −0.030 to 0.050); (β = 0.001, 95% CI = −0.010 to 0.010); (β = −0.001, 95% CI = −0.010 to 0.001), respectively, for early pregnancy. Bisphenols can significantly influence HPT axis hormones in adult males, females, and pregnant women. Gender-based studies were observed, concluding that adult females are more affected by bisphenol exposures than adult males. The subgroup analysis based on the regions did not reveal any associations.
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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 | 0.008 | 0.022 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.016 | 0.029 |
| Bibliometrics | 0.007 | 0.008 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
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".