Perfluoroalkyl substances and thyroid function in older adults

Abstract

Current understanding of the thyroid disruptive properties of perfluoroalkyl substances (PFASs), particularly in aging populations, is limited. The objectives of this study were to (i) assess associations between thyroid function, as measured by serum thyrotropin (thyroid stimulating hormone, TSH), free thyroxine (fT4), total thyroxine (T4), and total triiodothyronine (T3), and serum perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in an aging population and (ii) determine if other persistent organic pollutants with thyroid disruptive properties including polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) modify such associations. We conducted a cross-sectional study of 87 men and women 55 to 74 years of age, without clinically-diagnosed thyroid disease, who resided in upper Hudson River communities in New York. Geometric means (standard deviations) of serum PFOS and PFOA were 31.6 (1.7) ng/mL and 9.17 (1.72) ng/mL, respectively. Multivariable linear regression analyses indicated that one interquartile range difference in PFOS corresponded to 4% and 9% increases in fT4 and T4 respectively. We detected statistical interactions between PFOA and age for effects on fT4 and T4; joint increases in PFOA and age were associated with increases in fT4 and T4, of 3% and 7%, respectively. We also detected statistical interactions between PFOS and total PCBs for the effect on T3 and between PFOA and total PBDEs for the effect on TSH. Our results suggest that PFASs are associated with subtle alterations in thyroid hormone levels in this population, and that these associations are likely to vary by age, and levels of PCBs and PBDEs.

Placental Transfer of Perfluoroalkyl Substances and Associations with Thyroid Hormones: Beijing Prenatal Exposure Study

“…The concentrations of the major PFASs in our study were lower than most reported studies of populations in other countries 4 5 7 11 31 32 36 39 , but comparable with levels detected in other cities from China 6 50 and in recent studies of populations from Norway 51 , South Korea 40 , 20–40 years old females from the United States 36 and Denmark 52 . The highly correlated PFASs in maternal serum, especially PFNA, PFDA and PFUnA, indicated that these chemicals might have common sources of exposure in this area.…”

“…In human studies, associations between PFOA or PFOS and thyroid disease have been found in general population 26 and in highly exposed Mid-Ohio Valley community children, adults and workers 27 28 29 . However, the results of many other population-based researches on individual thyroid hormones disrupting potencies of PFASs were inconsistent 30 31 32 33 34 35 36 . Null associations between PFASs and thyroid hormones have been also reported 37 38 .…”

Association between perfluoroalkyl substances exposure and thyroid function in adults: A meta-analysis

“…However, the association is still inconclusive. Blood PFAS concentrations are negatively correlated with thyroid hormone concentrations according to some studies [ 23 , 25 , 26 ], while other studies showed positive correlations [ 27 , 28 ] or no association [ 29 – 32 ]. These inconsistent results may be due to the concentration-dependent differential effects of PFASs.…”

Per‐ and polyfluoroalkyl substances in Northern California cats: Temporal comparison and a possible link to cat hyperthyroidism

“…Epidemiologic and toxicologic studies have reported the potential of PFASs, particularly PFOAs and PFOSs, to act as endocrine-disruptors, impairing thyroid function through pathways including competing for thyroid hormone binding proteins, such as transthyretin (Weiss et al 2009;Ballesteros et al 2017). However, studies on human thyroid hormones and PFAS exposures have not been conclusive (Bloom et al 2010;Melzer et al 2010;Ji et al 2012;Webster et al 2014;Shrestha et al 2015;Yang et al 2016). Modest associations between PFOAs and thyroid hormones (negative for T4 and positive for T3) were reported in a study on 506 PFOA production workers (Olsen and Zobel 2007).…”