Perfluorinated Compounds and Thyroid Function in Older Adults

Abstract

Background: Perfluorinated compounds (PFCs) are widespread. PFCs may disrupt thyroid function; however, the human evidence is equivocal. Objectives: We assessed 1) predictors of serum perfluorooctanoic acid (PFOA) and perfluorooctane sulphonate (PFOS), and 2) associations between thyroid hormones and serum PFOA and PFOS among older men and women. Methods: Serum PFC levels were measured in 157 participants aged 55 -74 years. We used demographic variables and occupational information to identify predictors of serum PFOA and PFOS. We examined associations of serum PFOA and PFOS with serum thyroid stimulating hormone (TSH), free thyroxine (FT4), total thyroxine (T4), and total tri-iodothyronine (T3) in a subsample of men (n=51) and women (n=36) who were not taking sex hormones or thyroid medications. Linear regression models were used for both aims. Serum PFOA, PFOS, and TSH were log-natural transformed. Results: Geometric means (SD) of serum PFOS and PFOA were 34.2 (1.8) and 8.1 (1.7) ng/ml respectively, higher than the levels in NHANES 2003-2004 for men and women of the same age (22.8 (2.1) for PFOS and 3.9(2.1) for PFOA). Serum total PCB (lipid basis (ppb),p=0.02), occupational lead exposure (p=0.09), and low income (p<0.01) were predictors of PFOS; occupational solvent exposure (p=0.08), blood mercury (ng/dl, p=0.06), and area of residence (p=0.02) were PFOA predictors. Specific industries that were associated with elevated PFOS or PFOA included pulp and paper, color, chemical, and plastic manufacturing, military personnel, and general construction. Regarding thyroid biomarkers, PFOS was positively associated with both FT4 (? = 0.06, p=0.09) and T4 (? =0.87, p<0.01) adjusting for relevant confounders. These associations were stronger among women and older persons. Conclusion: The elevations in serum PFCs in this population appear to be related to occupation and are associated with increases in certain markers of thyroid function.