Academic journal article Environmental Health Perspectives

Maternal Urinary Triclosan Concentration in Relation to Maternal and Neonatal Thyroid Hormone Levels: A Prospective Study

Academic journal article Environmental Health Perspectives

Maternal Urinary Triclosan Concentration in Relation to Maternal and Neonatal Thyroid Hormone Levels: A Prospective Study

Article excerpt


Triclosan (TCS) is a synthetic liposoluble broad-spectrum bacteriostatic germicide to varieties of bacteria, fungi, and viruses (Ahn et al. 2008). It has been widely used in personal care products such as toothpastes, soaps, shampoos, and cosmetics with concentrations of 0.1-0.3% for more than 40 years (Jones et al. 2000). After being absorbed into the human body, TCS is mainly excreted via urine (Krishnan et al. 2010). In pregnant women, maternal serum TCS can pass through the placental barrier and reach the fetus, evidenced by its detection in the umbilical cord blood of newborns (Peters 2005).

The structure of TCS resembles thyroxine ([T.sub.4]), and previous researchers have found TCS might disrupt thyroid hormone levels (Allmyr et al. 2009; Dann and Hontela 2011). Animal studies have shown that TCS exposure significantly decreases serum totals of the hormones [T.sub.4] (Crofton et al. 2007; Paul et al. 2010) and triiodothyronine ([T.sub.3]) (Paul et al. 2010) in a dose-dependent manner in rats and reduced total [T.sub.4] in pregnant rats (Axelstad et al. 2013). A few epidemiologic studies have examined this topic in humans (Cullinan et al. 2012; Geens et al. 2015) and have generated conflicting results. Specifically, a recent study reported an inverse association between TCS and FT4 levels in women (Geens et al. 2015). An U.S. national study observed a positive association between TCS and total [T.sub.3] concentrations in adolescents (Koeppe et al. 2013).

Proper thyroid hormone levels are critical for fetal growth and maintaining pregnancy (Sarkhail et al. 2016). During early pregnancy, the fetus relies entirely on transplacental transfer of maternal thyroid hormones and normal maternal thyroid function (Patel et al. 2011). Maternal thyroid homeostasis also contributes substantially to fetal development during the remaining part of pregnancy (Patel et al. 2011). Even minor changes in thyroid homeostasis may affect fetal neurological development. For example, significant lower intelligence quotient (IQ) scores were observed in children of women with thyroid deficiency during pregnancy, even though hormone levels were inside the population reference range (Haddow et al. 1999; Morreale de Escobar et al. 2000).

Exposure to thyroid-disrupting chemicals may result in altered serum thyroid hormone levels, which may have adverse effects on developing fetuses. However, the effect of TCS exposure on maternal and neonatal thyroid hormone levels is unclear. To our knowledge, no previous study has examined this topic in pregnant women. Therefore, we aimed to evaluate the association between maternal TCS exposure and thyroid hormone levels of mothers and newborns.


Study Design and Participants

This study used data from the Shanghai Obesity and Allergy Cohort, a prospective birth cohort study initiated and maintained at the International Peace Maternity and Child Hospital (IPMCH) in Shanghai, China. The primary objective of this cohort study is to examine environmental and maternal risk factors of childhood obesity and allergic diseases. Eligible study participants were recruited at the IPMCH (n = 680) between June 2012 and February 2013. Eligibility criteria included singleton pregnancy, gestational age [greater than or equal to] 28 weeks, and Shanghai residency with intention to remain in Shanghai for the following 2 years. A face-to-face questionnaire interview was conducted at enrollment to collect demographic information including age, education level, maternal weight before pregnancy, and smoking and alcohol consumption before and during pregnancy. Medical history, including thyroid disease before and during pregnancy was abstracted from medical records. A spot urine sample was also collected for measuring TCS concentration during gestational weeks 38.8 [+ or -] 1.1 and was stored at -80[degrees]C until analysis. At the time of delivery, cord blood was collected from newborns and centrifuged to obtain the serum fractions. …

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