Association Between Phenols And Parabens & Reproductive And Thyroid Hormones

Introduction: Phenols and parabens are ubiquitous environmental contaminants. Evidence from animal studies suggest they may be endocrine disruptors. The association of phenols and parabens with reproductive and thyroid hormones was examined in the first 103 pregnant women (148 observations) recruited for a large prospective cohort. Methods: Urinary exposure biomarkers (bisphenol A, triclosan, benzophenone-3, 2,4-dichlorophenol, 2,5-dichlorophenol, butyl, methyl and propyl paraben) and serum hormone levels (estrogen, progesterone, sex hormone-binding globulin, free triiodothyronine, free thyroxine and thyroid stimulating hormone) were measured at two time points during pregnancy (16-20 weeks and 24-28 weeks). Linear mixed models with random intercept were constructed to examine the associations between the hormones and the exposures, controlling for specific gravity, maternal age, BMI and education. Progesterone, thyroid stimulating hormone and all exposure biomarkers were log-transformed. The results were additionally stratified by visit. Results: Sex hormone-binding globulin was positively associated with methyl paraben (p value = 0.02); free thyroxine (FT4) was positively associated with butyl paraben (p value = 0.01) and bisphenol A (p value = 0.04); free triiodothyronine (FT3) was negatively associated with benzophenone-3 (p value = 0.04); and, estrogen was negatively associated with butyl paraben (p value = 0.05). Suggestive, but not statistically significant, associations were also observed in this exploratory analysis. For example, progesterone was negatively associated with four of the phenols (p values= 0.15 – 0.17); and, thyroid stimulating hormone was positively associated with bisphenol A (p value = 0.15) and methyl paraben (p value = 0.11). Conclusions: In this group of women, phenols and parabens may be associated with reproductive and thyroid hormones which may lead to adverse health effects, but additional research is required.