Abstract
Phthalates are considered endocrine disruptors. Our study assessed the gender-specific effects of phthalate exposure on thyroid function in children. In total, 189 Taiwanese children were enrolled in the study. One-spot urine and blood samples were collected for analyzing 12 phthalate metabolites in urine and thyroid hormones. The association between urinary phthalate metabolites and serum thyroid hormones was determined using a generalized linear model with a log link function; the children were categorized into groups for analysis according to the 33rd and 66th percentiles. The data were stratified according to gender and adjusted for a priori defined covariates. In girls, a positive association existed between urinary di-2-ethylhexyl phthalate (DEHP) metabolites (mono-(2-ethylhexyl) phthalate, mono-(2-ethyl-5-oxohexyl) phthalate, and mono-(2-ethyl-5-hydroxyhexyl) phthalate) and free thyroxine (T4). In boys, urinary dibutyl phthalate (DBP) metabolites (mono-i-butyl phthalate and mono-n-butyl phthalate) were positively associated with free triiodothyronine (T3). After categorizing each exposure into three groups, urinary DEHP metabolites were positively associated with free T3 levels in boys. Our results suggested that DEHP is associated with free T4 in girls and that DBP is associated with free T3 in boys. Higher DEHP metabolite concentrations exerted larger effects on free T3 in boys. These results reveal the gender-specific relationships between phthalate metabolites and thyroid hormones.
Highlights
Phthalates have been used as plasticizers for a long time
Our results revealed that among the different types of phthalates, di-2-ethylhexyl phthalate (DEHP) and dibutyl phthalate (DBP) metabolites had the strongest effect on thyroid hormones in children aged 9–10
A positive association was discovered between DEHP exposure and free T4 in girls and between DBP exposure and free T3 in boys
Summary
Phthalates have been used as plasticizers for a long time. Humans are exposed to phthalates through multiple routes [1,2]. Phthalate esters are rapidly metabolized into monoesters and are further oxidized into oxidative metabolites in the human body, they have been associated with numerous serious health problems including endocrine disruption, reproductive and developmental toxicity, and respiratory allergy [3,4]. Res. Public Health 2017, 14, 123; doi:10.3390/ijerph14020123 www.mdpi.com/journal/ijerph
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