Association of diethylhexyl phthalate exposure with serum thyroid hormone levels: a systematic review and meta-analysis.

Objective: Evidence suggests that diethylhexyl phthalate (DEHP) may disrupt thyroid hormone homeostasis by targeting multiple components of the hypothalamic-pituitary-thyroid (HPT) axis, potentially harming human health. However, the relationship between DEHP exposure and thyroid function remains debated. We performed a meta-analysis to clarify the association between DEHP exposure and thyroid function.

Methods: We searched Medline, Embase, the Cochrane Library, and Web of Science for relevant studies that provided quantitative data on the association between DEHP and thyroid hormones. The ROBINS-E tool was used to assess the quality of included studies. Pearson correlation coefficients or regression coefficients (β) with 95% confidence intervals (CIs) were calculated to evaluate the relationship between DEHP exposure and thyroid hormone levels.

Results: Twenty-three studies were included. In adults, thyroxine (TT4) levels (pooled coefficient -0.05, 95% CI [-0.08, -0.03]) and free thyroxine (FT4) levels (pooled coefficient -0.04, 95% CI [-0.06, -0.02]) were negatively associated with urinary DEHP concentration. Additionally, DEHP exposure in adults was positively correlated with thyroid-stimulating hormone (TSH) levels (pooled coefficient 0.03, 95% CI [0.02, 0.04]). In pregnant women, urinary DEHP concentration was negatively correlated with FT4 levels (pooled correlation coefficient -0.04, 95% CI [-0.06, -0.02]). However, no significant association was observed between DEHP exposure and thyroid function in children and adolescents.

Conclusion: This meta-analysis demonstrates a significant association between DEHP exposure and serum thyroid hormone levels in adults. However, DEHP exposure appears to have no significant effect on thyroid function in children and adolescents.