Thyroid hormone levels associate with exposure to polychlorinated biphenyls and polybrominated biphenyls in adults exposed as children.
BACKGROUND
Michigan residents were directly exposed to endocrine-disrupting compounds, polybrominated biphenyl (PBB) and polychlorinated biphenyl (PCB). A growing body of evidence suggests that exposure to certain endocrine-disrupting compounds may affect thyroid function, especially in people exposed as children, but there are conflicting observations. In this study, we extend previous work by examining age of exposure's effect on the relationship between PBB exposure and thyroid function in a large group of individuals exposed to PBB.


METHODS
Linear regression models were used to test the association between serum measures of thyroid function (total thyroxine (T4), total triiodothyronine (T3), free T4, free T3, thyroid stimulating hormone (TSH), and free T3: free T4 ratio) and serum PBB and PCB levels in a cross-sectional analysis of 715 participants in the Michigan PBB Registry.


RESULTS
Higher PBB levels were associated with many thyroid hormones measures, including higher free T3 (p = 0.002), lower free T4 (p = 0.01), and higher free T3: free T4 ratio (p = 0.0001). Higher PCB levels were associated with higher free T4 (p = 0.0002), and higher free T3: free T4 ratio (p = 0.002). Importantly, the association between PBB and thyroid hormones was dependent on age at exposure. Among people exposed before age 16 (N = 446), higher PBB exposure was associated with higher total T3 (p = 0.01) and free T3 (p = 0.0003), lower free T4 (p = 0.04), and higher free T3: free T4 ratio (p = 0.0001). No significant associations were found among participants who were exposed after age 16. No significant associations were found between TSH and PBB or PCB in any of the analyses conducted.


CONCLUSIONS
This suggests that both PBB and PCB are associated with thyroid function, particularly among those who were exposed as children or prenatally.
['Curtis|Sarah W|SW|', 'Terrell|Metrecia L|ML|', 'Jacobson|Melanie H|MH|', 'Cobb|Dawayland O|DO|', 'Jiang|Victoria S|VS|', 'Neblett|Michael F|MF|', 'Gerkowicz|Sabrina A|SA|', 'Spencer|Jessica B|JB|', 'Marder|M Elizabeth|ME|', 'Barr|Dana Boyd|DB|', 'Conneely|Karen N|KN|', 'Smith|Alicia K|AK|0000-0002-8537-5156', 'Marcus|Michele|M|']
D000328:Adult D000368:Aged D003430:Cross-Sectional Studies D004781:Environmental Exposure D005260:Female D006801:Humans D008297:Male D008824:Michigan D008875:Middle Aged D011075:Polybrominated Biphenyls D011078:Polychlorinated Biphenyls D013963:Thyroid Hormones
PBB PCB Thyroxine Triiodothyronine Age at exposure Children’s health DOHaD EDC Endocrine disrupting compound Thyroid-stimulating hormone