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Meta-Analysis
. 2018 May 10;13(5):e0197244.
doi: 10.1371/journal.pone.0197244. eCollection 2018.

Association between perfluoroalkyl substances exposure and thyroid function in adults: A meta-analysis

Min Joo Kim  1 , Shinje Moon  2 , Byung-Chul Oh  3 , Dawoon Jung  4 , Kyunghee Ji  5 , Kyungho Choi  6 , Young Joo Park  1
Affiliations
Meta-Analysis

Association between perfluoroalkyl substances exposure and thyroid function in adults: A meta-analysis

Min Joo Kim et al. PLoS One. .

Abstract

Objective: Many people are exposed to perfluoroalkyl substances (PFASs) because these substances are widely used as industrial products. Although epidemiological studies suggest that PFASs can disrupt thyroid hormones, the association between PFAS exposure and thyroid function remains inconclusive. Therefore, we performed a comprehensive meta-analysis to investigate the association between PFASs exposure and thyroid hormones.

Methods: We searched medical literature databases for articles on the association between PFASs-perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and perfluorohexane sulfonic acid (PFHxS)-and thyroid hormone levels in adults. Twelve articles were included in the meta-analysis, and the pooled z values were calculated with correlation or regression coefficients.

Results: The blood PFOS concentration was positively correlated with free T4. The pooled z value was 0.05 (95% confidence interval (CI): 0.03, 0.08). PFOS was negatively correlated with total T4 and total T3 when excluding outlier studies. In a subgroup analysis stratified by mean PFOS concentration, PFOS was observed to be positively associated with free T4 and TSH and negatively associated with total T3 in the intermediate concentration group (8-16 ng/mL). PFOA concentration was negatively correlated with total T4 (z value, -0.06; 95% CI: -0.09, -0.03) after omitting one outlier study. PFHxS also showed a negative correlation with total T4 (z value, -0.04; 95% CI: -0.07, -0.01). A subgroup analysis of pregnant women showed that there was no association between PFASs and thyroid hormones.

Conclusions: Our meta-analysis suggests that PFASs are negatively associated with total T4, and their effect can be different depending on the PFAS concentration.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Representation of the search strategy based on PRISMA flow diagram.
Fig 2
Fig 2. Forest plots of the summary z value with corresponding 95% CIs for the correlation between PFOS and thyroid hormone.
A. Correlation between PFOS and free T4. B. Correlation between PFOS and total T4. C. Correlation between PFOS and total T3 D. Correlation between PFOS and TSH.CI, confidence interval; W, weight.
Fig 3
Fig 3. Forest plots of the summary z value with corresponding 95% CIs for the correlation between PFOA and thyroid hormone.
A. Correlation between PFOA and free T4. B. Correlation between PFOA and total T4. C. Correlation between PFOA and total T3 D. Correlation between PFOA and TSH.CI, confidence interval; W, weight.
Fig 4
Fig 4. Forest plots of the summary z value with corresponding 95% CIs for the correlation between PFHxS and thyroid hormone.
A. Correlation between PFHxS and free T4. B. Correlation between PFHxS and total T4. C. Correlation between PFHxS and total T3 D. Correlation between PFHxS and TSH.CI, confidence interval; W, weight.
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