Paraben exposure profiles in pregnant women and association with changes in thyroid hormone levels

Parabens are widely suspected to be endocrine disruptors. Exposure during pregnancy may interfere with thyroid hormone homeostasis, resulting in adverse effects on neurodevelopment and fetal growth. This study aimed to assess pregnant women's exposure to parabens and possible associations with changes in thyroid hormone levels during pregnancy. Links between exposure sources and endogenous paraben concentrations were also investigated. This descriptive study included 384 pregnant women. Thyroid hormones and thyroid-stimulating hormone (TSH) were measured on electrochemiluminescence. Parabens (methylparaben [MP], ethylparaben [EP] and propylparaben [PP]) were detected on LC-MS/MS. Parabens were found in almost all pregnant women (MP: 96.9%; EP: 89.3%; PP: 94.5%), at varying ranges of μg/g creatinine (MP: 36.633±39.849; EP: 9.721±15.655; PP: 22.109±20.722). There were significant negative associations between urinary concentrations of PP and plasma levels of TSH and free thyroxine (FT4). Analysis of exposure sources revealed significant associations of urinary levels of EP with exposure to facial care products and sunscreens. This research highlights the alarming rate of exposure to parabens, which may have deleterious effects on thyroid hormone levels in pregnant women, with consequent repercussions on fetal neural development.