Document Detail

Associations between Perfluoroalkyl acids (PFASs) and maternal thyroid hormones in early pregnancy: A population-based cohort study.
MedLine Citation:
PMID:  25019470     Owner:  NLM     Status:  Publisher    
BACKGROUND: Associations between perfluoroalkyl acids (PFASs) and human thyroid hormone levels remain unclear, especially during early pregnancy when small changes in maternal thyroid hormones can affect fetal brain development.
OBJECTIVES: To examine associations between maternal serum PFAS levels and maternal thyroid hormone levels in the early 2nd trimester of pregnancy.
METHODS: Participants were euthyroid pregnant women (n=152) enrolled in the Chemicals, Health and Pregnancy (CHirP) study based in Vancouver, Canada. Associations between maternal serum PFASs, including perfluorohexanesulfonate (PFHxS), perfluorononanoate (PFNA), perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) and repeated measures of maternal thyroid hormones, including free thyroxine (fT4), total thyroxine (TT4) and thyroid stimulating home (TSH) were examined using mixed effects linear models. Associations were considered in all women, then separately in women with high (≥9IU/mL) vs normal (<9IU/mL) levels of thyroid peroxidase antibody (TPOAb), a marker of autoimmune hypothyroidism (Hashimoto׳s disease).
RESULTS: Median PFAS concentrations (ng/mL) in maternal sera were 1.0 (PFHxS), 0.6 (PFNA), 1.7 (PFOA) and 4.8 (PFOS). PFASs were not associated with fT4, TT4 or TSH among women with normal TPOAb. However, among the 9% of women with high TPOAb (n=14), interquartile range (IQR) increases of PFASs were associated with a 46-69% increase in maternal TSH (95% CIs ranging from 8% to 123%) (PFNA, PFOA and PFOS only), and with a 3% to 7% decrease in maternal fT4 (95% CIs ranging from -18% to 5%) (all 4 PFASs). PFNA was also associated with higher maternal TSH in the whole sample.
CONCLUSIONS: PFASs were positively associated with TSH, and weakly negatively associated with fT4 in the subset of pregnant women with high TPOAb, which occurs in 6-10% of pregnancies. PFASs may exacerbate the already high TSH and low fT4 levels in these women during early pregnancy, which is a critical time of thyroid hormone-mediated fetal brain development. The clinical significance of these findings is not clear. We propose a "multiple hit hypothesis" to explain these findings; this hypothesis deserves evaluation in larger, more representative study samples.
Glenys M Webster; Scott A Venners; Andre Mattman; Jonathan W Martin
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2014-7-11
Journal Detail:
Title:  Environmental research     Volume:  133C     ISSN:  1096-0953     ISO Abbreviation:  Environ. Res.     Publication Date:  2014 Jul 
Date Detail:
Created Date:  2014-7-14     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0147621     Medline TA:  Environ Res     Country:  -    
Other Details:
Languages:  ENG     Pagination:  338-347     Citation Subset:  -    
Copyright Information:
Copyright © 2014 Elsevier Inc. All rights reserved.
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