Association between urinary 3 5 6-trichloro-2-pyridinol a metabolite of chlorpyrifos and chlorpyrifos-methyl and serum T4 and TSH in NHANES 1999–2002

摘要

Thyroid hormones are vital to a host of human physiological functions in both children and adults. Exposures to chemicals, including chlorpyrifos, have been found to modify thyroid signaling at environmentally relevant levels in animal studies. The aim of this study was to examine circulating T4 and TSH levels in relation to urinary concentrations of 3, 5, 6-trichloro-2-pyridinol (TCPY), a metabolite of the organophosphorus insecticides chlorpyrifos and chlorpyrifos-methyl, using data from individuals 12 years and older from the U.S. National Health and Nutrition Examination Surveys (NHANES). NHANES datasets from and were combined, and individuals with thyroid disease, those taking thyroid medications, and pregnant women were excluded (N=3249). Multivariable linear regression models for relationships between log-transformed urinary TCPY and serum total T4 or log (TSH) were constructed adjusting for important covariates. Models were stratified by sex and a categorical age variable (12–18, 18–40, 40–60, and >60 years). In male participants, an interquartile range (IQR) increase in urinary TCPY was associated with statistically significant increases in serum T4 of 3.8% (95^th CI 0.75 to 7.0)among those 12–18 years of age and 3.5% (95^th CI 0.13 to 7.0) in the 18–40 year age group., relative to median T4 levels using unweighted models. An IQR increase in TCPY was also associated with decreases in TSH of 10.7% (−18.7–2.05) among men 18–40 years old and 20.0% (95^th CI −28.9 to −9.86) among men >60 years old. Conversely, urinary TCPY was positively associated with TSH in females >60 years of age. Further research to confirm these findings, elucidate mechanisms of action, and explore the clinical and public health significance of such alterations in thyroid hormones is needed.