Exposure to phthalates in children aged 5-7Â years: Associations with thyroid function and insulin-like growth factors

This study aimed to evaluate the associations between phthalate concentrations and thyroid function in preschool children. We collected demographic data and biological samples from 216 children aged 5-7 years. We calculated urinary concentrations of eight mono-phthalate metabolites (mPAEs) separately for children from urban and rural areas and investigated their associations with thyroid function and growth hormones. mPAE concentrations were higher in children from the urban area than in those from the rural area, and most mPAEs were positively associated with free triiodothyronine and free thyroxine. The insulin-like growth factor 1 (IGF-1) concentration decreased 0.082 ng/mL (95% confidence interval [CI]: − 1.34, − 0.113) with each 1 ng/mL increase in monomethyl phthalate (MMP) and 0.132 ng/mL (95% CI: − 0.209, − 0.055) with each 1 ng/mL increase in mono-n-butyl phthalate. The insulin-like growth factor binding protein 3 concentration decreased by 0.01 mg/L (95% CI: − 0.001, − 0.000) or 0.01 mg/L (95% CI: − 0.003, − 0.000) with each 1 ng/mL increase in MMP or monoethyl phthalate, respectively. Exposure to some phthalates at 5-7 years of age might interfere with thyroid hormones and growth.