Presentations

Abstract

Introduction: Benzophenone-3 (BP-3), a sunscreen ingredient, is suggested to have endocrine-disrupting properties by interacting with hormone receptors and altering gene expression. In animal studies, BP-3 affects thyroid function by enhancing gene expressions related to thyroid hormone production, iodine uptake, and peripheral conversion of T4 to T3. However, small epidemiological studies in humans have provided inconsistent results. Therefore, we examined the association between BP-3 and thyroid hormones using the nationally representative US population.

Methods: We used the continuous NHANES data from 2007-08 and 2011-12. Urinary BP-3 and urinary creatinine were used to calculate creatinine-normalized urinary BP-3 (CNBP3) to account for urinary dilution/concentration. Relationship between quartiles of BP-3 and thyroid stimulating hormone (TSH), thyroxine (T4), free T4, triiodothyronine (T3), and free T3 were examined using survey-weighted multivariable generalized linear regression models. Models were adjusted for age, gender, race, smoking, hypertension, diabetes mellitus, obesity, estimated glomerular filtration rate (eGFR), and serum albumin.

Results: Of the 3,966 participants, 1,985 (50%) were female, with a median (IQR) age of 42.9 (36.9) years. The cohort included 1,597 (40.3%) Whites, 905 (22.8%) Blacks, and 1,035 (26.1%) Hispanics, with a median (IQR) BP-3 level of 12.5 (47.5) µg/gm (Table 1). In unadjusted models, participants in the highest quartile of CNBP3 levels had 3% lower T4 levels compared to those in the lowest quartile (0.97; 95% CI: 0.95, 0.99; p=0.007). This association remained significant after adjustment (0.96; 95% CI: 0.94, 0.98; p=0.001). Similarly, the highest quartile of CNBP3 was associated with a 3% reduction in T3 levels in adjusted analyses (Table 2). There was no association between TSH, free T4, or free T3 and CNBP3.

Conclusion: In this large, nationally representative cohort, we found that higher levels of CNBP3 are associated with modest but significant reductions in T4 and T3. However, no significant relationship was seen with free T4, free T3, or TSH levels, suggesting that the functional thyroid hormones levels remain unchanged after CNBP3 exposure. Therefore, in the context of thyroid function, use of BP-3-containing sunscreens has no deleterious effects.