BACKGROUND AND AIM[|]The objective of this analysis is to evaluate the cross-sectional associations of multiple per and polyfluoroalkyl substances (PFAS) with thyroid hormone levels in women without thyroid disease.[¤]METHOD[|]We used enrollment data (2020-2021) from the GenX Cohort Study, a prospective study of PFAS exposure and health in the Cape Fear River Basin of North Carolina (NC). We restricted analysis to women without a self-reported history of thyroid disease. Serum samples were analyzed for a suite of PFAS using high resolution mass spectrometry and for thyroid hormones (TSH, free T4, and Total T4) by immunoassay. Covariate information was obtained via questionnaire. We limited analysis to five PFAS detected in 75% of samples (PFHpS, PFHxS, PFNA, PFOS, and PFOA). We used multiple linear regression controlling for age, smoking status, current alcohol consumption, and race. Models included all five PFAS simultaneously to control for multiple exposures; serum PFAS were modeled as continuous variables. Separate models were built for each log-transformed thyroid hormone.[¤]RESULTS[|]The study sample of 367 women ranges in age from 18 to 93 years old. Hormone values were within normal ranges. Serum PFAS values for all five PFAS were higher than US national values. PFOS had the highest median concentration (5.9 ng/mL) while PFHpS had the lowest median concentration (0.3 ng/mL). The Spearman correlations among PFAS ranged from 0.5 to 0.8, with the strongest correlation between PFOS and PFNA. Overall, free T4 was the most sensitive outcome, with both PFOS and PFHpS significantly associated with increased free T4; PFHpS was also positively associated with Total T4. No PFAS were associated with TSH.[¤]CONCLUSIONS[|]In this cross-sectional study of thyroid hormones and PFAS in a highly exposed community, sulfonic acid PFAS (e.g., PFOS), but not carboxylic acid PFAS (e.g, PFOA), were positively associated with T4 (free and total) in women.[¤]