Mediation effects of thyroid function in the associations between phthalate exposure and glucose metabolism in adults. (1st June 2021)

• Record Type: Journal Article
• Authors: Huang, Han-Bin; Siao, Chi-Ying; Lo, Yuan-Ting C.; Shih, Shu-Fang; Lu, Chieh-Hua; Huang, Po-Chin
• Is Part Of: Environmental pollution. Volume 278(2021)
• Publication Date: 2021-06-01
• Subjects: Phthalates -- Thyroid hormones -- Insulin resistance -- Glucose metabolism -- Mediation effects; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2021.116799
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: The mediating influence of thyroid function on the association of phthalate exposure with glucose metabolism, including insulin resistance, remains unclear. We explored the mediating influence of thyroid hormone levels on the phthalate exposure–insulin resistance association. This cross-sectional study of 217 Taiwanese adults assessed insulin resistance (Homeostatic Model Assessment for Insulin Resistance, HOMA-IR scores) and the levels of 11 urinary phthalate metabolites and 5 thyroid hormones. Multiple regression models were used to analyze the associations among serum thyroid hormone levels, urinary phthalate metabolite levels, and HOMA-IR scores. The mediation analysis assessed the influence of thyroid function on the phthalate exposure–HOMA-IR association. Our data indicated urinary mono-ethylhexyl phthalate (MEHP) levels was negatively associated with free thyroxine (T4 ) (β = −0.018; 95% confidence interval [CI]: −0.031, −0.005) and positively associated with HOMA-IR scores (β = 0.051, 95% CI: 0.012, 0.090). The study also revealed urinary mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP) levels was negatively associated with free T4 (β = −0.036, 95% CI: −0.056, −0.017) and HOMA-IR (β = 0.070, 95% CI: 0.013, 0.126). Free T4 and HOMA-IR had a negative association (β = −0.757, 95% CI: −1.122, −0.392). In the mediation analysis, free T4 mediated 24% and 35% of the associations of urinary MEHP and MEOHP with HOMA-IR, respectively. Our findings revealed the mediating role of thyroid function in the phthalate exposure–glucose metabolism association in adults. Graphical abstract: Image 1 Highlights: We examined the mediation role of thyroid hormones in the associations between exposure to phthalates and insulin resistance. Associations of urinary MEHP (24%) and MEOHP (35%) with HOMA-IR were partially mediated by free T4. Free T4 levels could play a mediating role in the effects of exposure to phthalates on insulin resistance in adults. Abstract : Our data provided the evidence supported how phthalate exposure influence glucose metabolism through mediating role of thyroid hormones.