Does exposure to phthalates influence thyroid function and growth hormone homeostasis? The Taiwan Environmental Survey for Toxicants (TEST) 2013

Environ Res. 2017 Feb;153:63-72. doi: 10.1016/j.envres.2016.11.014. Epub 2016 Nov 29.

Abstract

Background: Previous epidemiologic and toxicological studies provide some inconsistent evidence that exposure to phthalates may affect thyroid function and growth hormone homeostasis.

Objective: To assess the relations between exposure to phthalates and indicators of thyroid function and growth hormone homeostasis disturbances both among adults and minors.

Methods: We conducted a population-based cross-sectional study of 279 Taiwanese adults (≥18 years old) and 79 minors (<18 years old) in 2013. Exposure assessment was based on urinary biomarkers, 11 phthalate metabolites measured by using online liquid chromatography/tandem mass spectrometry. Indicators of thyroid function included serum levels of thyroxine (T4), free T4, triiodothyronine, thyroid-stimulating hormone, and thyroxine-binding globulin (TBG). Growth hormone homeostasis was measured as the serum levels of insulin-like growth factor 1 (IGF-1) and insulin-like growth factor binding protein 3 (IGFBP3). We applied multivariate linear regression models to examine these associations after adjusting for covariates.

Results: Among adults, serum T4 levels were negatively associated with urinary mono-(2-ethyl-5-hydroxyhexyl) phthalate (β=-0.028, P=0.043) and the sum of urinary di-(2-ethylhexyl) phthalate (DEHP) metabolite (β=-0.045, P=0.017) levels. Free T4 levels were negatively associated with urinary mono-ethylhexyl phthalate (MEHP) (β=-0.013, P=0.042) and mono-(2-ethyl-5-oxohexyl) phthalate (β=-0.030, P=0.003) levels, but positively associated with urinary monoethyl phthalate (β=0.014, P=0.037) after adjustment for age, BMI, gender, urinary creatinine levels, and TBG levels. Postive associations between urinary MEHP levels and IGF-1 levels (β=0.033, P=0.006) were observed. Among minors, free T4 was positively associated with urinary mono benzyl phthalate levels (β=0.044, P=0.001), and IGF-1 levels were negatively associated with the sum of urinary DEHP metabolite levels (β=-0.166, P=0.041) after adjustment for significant covariance and IGFBP3.

Conclusions: Our results are consistent with the hypothesis that exposure to phthalates influences thyroid function and growth hormone homeostasis.

Keywords: Biomonitoring; Growth hormone; Phthalate metabolites; Taiwanese; Thyroid hormones.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Child
  • Cross-Sectional Studies
  • Diethylhexyl Phthalate / metabolism
  • Diethylhexyl Phthalate / urine
  • Environmental Exposure / adverse effects*
  • Environmental Exposure / analysis
  • Environmental Pollutants / toxicity*
  • Female
  • Homeostasis
  • Humans
  • Insulin-Like Growth Factor Binding Protein 3 / blood
  • Insulin-Like Growth Factor I / analysis
  • Insulin-Like Growth Factor I / metabolism
  • Male
  • Middle Aged
  • Phthalic Acids / toxicity*
  • Phthalic Acids / urine
  • Taiwan
  • Thyroid Gland / drug effects*
  • Thyroid Gland / physiology
  • Thyroid Hormones / blood*
  • Thyroxine / blood

Substances

  • Environmental Pollutants
  • IGFBP3 protein, human
  • Insulin-Like Growth Factor Binding Protein 3
  • Phthalic Acids
  • Thyroid Hormones
  • Insulin-Like Growth Factor I
  • phthalic acid
  • Diethylhexyl Phthalate
  • Thyroxine