Prenatal and early childhood phthalate exposures and thyroid function among school-age children

Kyoung Nam Kim, Hwa Young Kim, Youn Hee Lim, Choong Ho Shin, Johanna Inhyang Kim, Bung Nyun Kim, Young Ah Lee, Yun Chul Hong

Research output: Contribution to journalArticle

Abstract

Background: Limited studies have investigated the association between prenatal and early childhood phthalate exposures and thyroid function among children. Objectives: To investigate the association between early life phthalate exposure and thyroid function among school-age children, considering both prenatal and early childhood exposures, using longitudinal data from an established prospective cohort. Methods: We measured urinary phthalate metabolite levels during pregnancy and at 2, 4, and 6 years of age and conducted thyroid function tests at 6 years of age. We assessed the associations between phthalate metabolite levels and thyroid function using linear regression and Bayesian kernel machine regression (BKMR) models (n = 492). Results: In linear regression models, a doubling of urinary mono-n-butyl phthalate (MnBP) levels, measured during pregnancy and at 4 years of age, was associated with lower thyroid-stimulating hormone (TSH) levels at 6 years of age (−5.0%, 95% confidence interval [CI]: −8.8%, −1.0% and −5.7%, 95% CI: −9.7%, −1.5%, respectively). A similar association was found between mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP) levels at 4 years of age and TSH levels at 6 years of age (−5.5%, 95% CI: −9.7%, −1.1%). Urinary mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) (2.3%, 95% CI: 0.1%, 4.5%) and MEOHP levels at 2 years of age (2.2%, 95% CI: 0.1%, 4.4%) and mono-2-ethyl-5-carboxypentyl phthalate (1.4%, 95% CI: 0.1%, 2.7%) and mono-benzyl phthalate levels at 6 years of age (1.1%, 95% CI: 0.4%, 1.9%) were associated with higher triiodothyronine (T3) levels at 6 years of age. Urinary MnBP during pregnancy, MEHHP, MEOHP, and MnBP at 4 years of age were also associated with lower free thyroxine (fT4) × TSH. In BKMR models, urinary MnBP levels during pregnancy were associated with lower TSH levels and fT4 × TSH (both posterior inclusion probabilities: 0.99). Conclusions: Our findings suggest that early life phthalate exposure influences subsequent thyroid function. However, the results should be interpreted cautiously, because a single spot urine sample was used to quantify the phthalate exposures at each time point.

Original languageEnglish
Article number105782
JournalEnvironment International
Volume141
DOIs
StatePublished - Aug 2020

Keywords

  • Bayesian kernel machine regression
  • Children
  • Cohort
  • Phthalate
  • Thyroid

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