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

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 beta 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.