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. 2011 Oct;119(10):1396-402.
doi: 10.1289/ehp.1103582. Epub 2011 Jul 11.

Relationship between urinary phthalate and bisphenol A concentrations and serum thyroid measures in U.S. adults and adolescents from the National Health and Nutrition Examination Survey (NHANES) 2007-2008

John D Meeker  1 , Kelly K Ferguson
Affiliations

Relationship between urinary phthalate and bisphenol A concentrations and serum thyroid measures in U.S. adults and adolescents from the National Health and Nutrition Examination Survey (NHANES) 2007-2008

John D Meeker et al. Environ Health Perspect. 2011 Oct.

Abstract

Background: Limited animal, in vitro, and human studies have reported that exposure to phthalates or bisphenol A (BPA) may affect thyroid signaling.

Objective: We explored the cross-sectional relationship between urinary concentrations of metabolites of di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), and BPA with a panel of serum thyroid measures among a representative sample of U.S. adults and adolescents.

Methods: We analyzed data on urinary biomarkers of exposure to phthalates and BPA, serum thyroid measures, and important covariates from 1,346 adults (ages ≥ 20 years) and 329 adolescents (ages 12-19 years) from the National Health and Nutrition Examination Survey (NHANES) 2007-2008 using multivariable linear regression.

Results: Among adults, we observed significant inverse relationships between urinary DEHP metabolites and total thyroxine (T4), free T4, total triiodothyronine (T3), and thyroglobulin, and positive relationships with thyroid-stimulating hormone (TSH). The strongest and most consistent relationships involved total T4, where adjusted regression coefficients for quintiles of oxidative DEHP metabolites displayed monotonic dose-dependent decreases in total T4 (p-value for trend < 0.0001). Suggestive inverse relationships between urinary BPA and total T4 and TSH were also observed. Conversely, among adolescents, we observed significant positive relationships between DEHP metabolites and total T3. Mono(3-carboxypropyl) phthalate, a secondary metabolite of both DBP and di-n-octyl phthalate, was associated with several thyroid measures in both age groups, whereas other DBP metabolites were not associated with thyroid measures.

Conclusions: These results support previous reports of associations between phthalates-and possibly BPA--and altered thyroid hormones. More detailed studies are needed to determine the temporal relationships and potential clinical and public health implications of these associations.

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Conflict of interest statement

The authors declare they have no actual or potential competing financial interests.

Figures

Figure 1
Figure 1
Adjusted regression coefficients [β (95% CI)] for change in serum thyroid measure in relation to urinary MEHHP quintiles (p-value for trend) for (A) total T4 (< 0.0001), (B) free T4 (0.09), (C) free T3 (0.20), and (D) TSH (0.06). Values are adjusted for age, sex, race, BMI, ln-serum cotinine, ln-urinary creatinine, and ln‑urinary iodine.
Figure 2
Figure 2
Adjusted regression coefficients [β (95% CI)] for change in serum thyroid measure in relation to urinary BPA quintiles (p-value for trend) for (A) total T4 (0.05), (B) free T4 (0.89), (C) free T3 (0.80), and (D) TSH (0.14). Values are adjusted for age, sex, race, BMI, ln-serum cotinine, ln-urinary creatinine, and ln-urinary iodine.
See this image and copyright information in PMC

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