Context: Perfluorinated chemicals (PFCs) have been widely used in a variety of products worldwide for years. The relationship between serum PFCs and thyroid function has never been addressed in a nationally representative survey.
Objectives: The study examined the association between serum PFCs and thyroid function in the general U.S. population.
Design and participants: We selected 1181 subjects (aged >20 years) from a National Health and Nutrition Examination Survey (NHANES) in 2007 through 2008 and 2009 through 2010 to determine the relationship between serum PFCs and thyroid function. Data were adjusted for confounding variables.
Results: The geometric means and 95% confidence interval (CI) concentrations of perfluorooctanoate (PFOA), perfluorooctane sulfonate, perfluorononanoic acid, and perfluorohexane sulfonate (PFHxS) were 4.15 (4.02-4.29), 14.2 (13.59-14.86), 1.54 (1.48-1.59), and 2.00 (1.89-2.11) ng/mL, respectively. After weighting for sampling strategy, we determined a 1-U increase in natural log-serum PFOA increased serum total T3 concentration by 6.628 ng/dL (95% CI = 0.545-12.712, P = .035) in women. A 1-U increase in natural log-PFHxS was associated with an increase of total T4 by 0.26 μg/mL (95% CI = 0.108-0.413, P = .002) and total T3 by 4.074 ng/dL (95% CI = 2.232-5.916, P < .001) in women and a decrease of natural log-free T4 by 0.016 (ng/dL) (95% CI = -0.029 to 0.003, P = .019) in men.
Conclusion: Higher serum concentrations of PFOA and PFHxS are associated with total T3, total T4, and free T4 in the U.S. general population. More studies are warranted to clarify the causal relationship between PFCs and thyroid function.