PFAS Exposure Can Impair Thyroid Homeostasis in Adults

TOPLINE:
Exposure to individual or mixed per- and polyfluoroalkyl substances (PFASs) is associated with changes in peripheral rather than central thyroid hormone sensitivity.
METHODOLOGY:
PFASs are widely recognized for their persistence in the environment and potential endocrine-disrupting effects.
A cross-sectional study investigated associations between PFAS exposures and thyroid homeostasis parameters in adult participants in two National Health and Nutrition Examination Survey cycles (2007-2008 and 2011-2012).
Participants were required to have complete thyroid hormone profiles and measurements of PFAS concentration, not be pregnant, and not have thyroid disease or a history of using thyroid drugs such as thyroxine, methimazole, and propylthiouracil.
Levels of six PFASs were measured in the serum: Perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorononanoic acid (PFNA), perfluorodecanoic acid, perfluorohexane sulfonic acid (PFHxS), and 2-(N-methyl-perfluorooctane sulfonamido) acetic acid.
Thyroid homeostasis parameters were assessed using serum concentrations of thyroid hormones.Peripheral sensitivity was calculated using the ratio of free triiodothyronine to free thyroxine (FT3/FT4) and the sum activity of peripheral deiodinases (SPINA-GD).Central sensitivity was assessed with thyrotroph thyroxine resistance index, thyroid-stimulating hormone index, thyroid feedback quantile–based index (TFQI), and parametric TFQI.
Peripheral sensitivity was calculated using the ratio of free triiodothyronine to free thyroxine (FT3/FT4) and the sum activity of peripheral deiodinases (SPINA-GD).
Central sensitivity was assessed with thyrotroph thyroxine resistance index, thyroid-stimulating hormone index, thyroid feedback quantile–based index (TFQI), and parametric TFQI.
TAKEAWAY:
Researchers included 2386 adults (mean age, 47.59 years; 53.94% men; 42.88% White).
FT3/FT4 and SPINA-GD were positively associated with PFOA, PFOS, PFNA, and PFHxS (P < .05 for all) in an adjusted analysis; however, no link was found between central thyroid sensitivity parameters and PFAS exposures.
Specifically, higher quartiles of PFOA and PFOS concentrations were associated with an increased FT3/FT4 and SPINA-GD, indicating an increased conversion efficiency of FT4 to FT3 or peripheral deiodinase.
Exposure to a mixture of different PFASs was also positively correlated with FT3/FT4 (β, 0.013; P < .001) and SPINA-GD (β, 1.230; P < .001), with PFOA showing the highest contribution.
Men and smokers showed higher correlations of PFOA with peripheral thyroid hormone sensitivity indicators than women and nonsmokers, respectively.
IN PRACTICE:
“PFAS exposure, especially PFOA and PFOS, mainly impacted peripheral sensitivity to thyroid hormones, instead of central sensitivity,” the authors wrote, adding that their results may support, “taking more steps to prevent and reduce” the harmful effects of PFASs.
SOURCE:
This study was led by Xinwen Yu and Yufei Liu, Department of Endocrinology, The Second Affiliated Hospital of Air Force Medical University, Xi’an, China. It was published online in The Journal of Clinical Endocrinology & Metabolism.
LIMITATIONS:
The cross-sectional design of this study limited the ability to establish causal relationships between PFAS exposure and thyroid function. The assessment of thyroid homeostasis parameters was conducted indirectly by measuring thyroid hormone levels. Inaccuracies in self-reported data on long-term exposure to PFASs and the exclusion of other endocrine-disrupting chemicals may have affected the study’s conclusions.
DISCLOSURES:
This study was supported by grants from the Natural Science Foundation of Shaanxi Province, China; the Key Research and Development Project of Shaanxi Province; and the Clinical Research Program of Air Force Medical University. The authors reported having no relevant conflicts of interest.
This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.
 
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