BackgroundVarious studies have reported interactions between thyroid hormones and early life chemical exposure. Our objective was to analyze the associations between markers of endocrine-disrupting chemical exposure and thyroid function in newborns, determined through heel prick blood spots.MethodsThree European mother-child cohorts (FLEHSI-Belgium, HUMIS-Norway, and the PCB cohort-Slovakia. Total n=1,784) were pooled for the purpose of this study. Data on thyroid-stimulating hormone (TSH) were obtained from national neonatal screening registries, and samples of cord plasma and/or breast milk were collected to determine exposure to various chemicals. Multiple regression models were composed with exposure and cohort as fixed factors, and adjustments were made for a priori defined covariates.ResultsMedian TSH concentrations were 1, 1.10, and 2.76 mU/l for the Belgian, Norwegian, and Slovak cohorts, respectively. For polychlorinated biphenyl (PCB)-153 and dichlorodiphenyldichloroethylene (p,p'-DDE), children in the third exposure quartile had a 12-15% lower TSH at birth. Results remained unchanged after additional adjustment for birth weight and gestational weight gain. No effect on TSH was observed for the other compounds.ConclusionEarly life exposure to PCB-153 and p,p'-DDE impacts newborn TSH levels. Higher exposure levels were associated with 12-15% lower TSH levels.