Association between serum levels of 4-tertiary-octylphenol and thyroid function in a young cohort study

• The correlations among 4-tOP and thyroid function was studied in 886 young population. • Positive associations were found among 4-tOP, total T3, and free T4. • A upward trend of total T3 and free T4 with increasing quartiles of 4-t-OP. • No link between 4-t-OP and thyroid disease, but caution is needed due to few cases. 4-tertiary-octylphenol (4-t-OP) is a commonly used alkylphenol present in a variety of consumer products. Earlier experimental investigations have suggested that 4-t-OP leads to thyroid dysfunction. However, it is unclear whether these effects translate to humans. We recruited 886 adolescents and young adults (aged 12–30 years) from Taiwan and explored the associations between serum levels of 4-t-OP and various thyroid panel parameters including free and total thyroxine (T4) and triiodothyronine (T3), thyroid-stimulating hormone (TSH), and thyroxine-binding globulin (TBG). Our findings indicated that a one-unit increase in the natural logarithm (ln) of 4-t-OP levels was positively associated with both total T3 and ln free T4, with β values of 3.122 (SE = 1.400, P = 0.026) and 0.046 (SE = 0.015, P = 0.002), respectively. Furthermore, we observed a statistically significant upward trend in the mean values of total T3 and ln free T4 as the quartiles of 4-t-OP exposure increased ( P for trend = 0.001 and 0.025, respectively). Nevertheless, our analysis did not uncover any differences in the odds ratio of thyroid diseases based on exposure to 4-t-OP in the logistic regression analysis. In conclusion, our study reveals an association between serum concentrations of 4-t-OP and biomarkers of thyroid function. However, these effects may manifest as subclinical. Further investigations are essential to establish a causal relationship between 4-t-OP exposure and thyroid function in human subjects.