title: Systematic analysis of the relationship between standardized biological levels of polychlorinated biphenyls and thyroid function in pregnant women and newborns.
abstract: The impact polychlorinated biphenyl (PCB) exposure on thyroid status in pregnant women and newborns was investigated in various epidemiological studies, but findings show inconsistencies, and differences in biological indicators of exposure between studies limits comparison of results. The aim of this research was to use a procedure previously developed to standardize PCB biological concentration data between published studies to perform a systematic analysis of associations between PCB exposure and thyroid hormones (THs) (total and free T3 and T4) or thyroid stimulating hormone (TSH) in pregnant women and newborns. Biological concentrations from nineteen studies were expressed in total PCB equivalent per kg of lipids in maternal plasma (μg PCBMPEQ kg(-1) lipids). Systematic analysis of the "standardized biological concentration-thyroid parameters" relationship was conducted through the application of methodological criteria in both pregnant women and newborns. Standardization of PCB levels and application of methodological criteria led to assign higher confidence to ten of the reviewed studies. Among the retained studies in pregnant women, only one reported a significant association between PCBs and total T3 levels, but no association were observed when circulating TSH and free T4 levels were used to assess thyroid function. Regarding the association between prenatal PCB exposure and thyroid status in newborns, a lack of significant association was consistently obtained in the retained studies assigned an overall high confidence. The weight of evidence of a significant impact of PCB exposure on TSH and TH levels at the described biological levels in pregnant women and newborns (mean<1000 μg PCBMPEQ kg(-1) lipids) appears low according to this systematical analysis.
authors.affiliation: Département de Santé Environnementale et Santé au Travail, Chaire d'analyse et de Gestion des Risques Toxicologiques and Institut de Recherche en Santé Publique de l'Université de Montréal (IRSPUM), Faculty of Medicine, Université de Montréal, P.O. Box 6128, Main Station, Montreal, Quebec H3C 3J7, Canada.
authors.forename: Naïma
authors.initials: N
authors.lastname: El Majidi
authors.affiliation: Département de Santé Environnementale et Santé au Travail, Chaire d'analyse et de Gestion des Risques Toxicologiques and Institut de Recherche en Santé Publique de l'Université de Montréal (IRSPUM), Faculty of Medicine, Université de Montréal, P.O. Box 6128, Main Station, Montreal, Quebec H3C 3J7, Canada. Electronic address: michele.bouchard@umontreal.ca.
authors.forename: Michèle
authors.initials: M
authors.lastname: Bouchard
authors.affiliation: Département de Santé Environnementale et Santé au Travail, Chaire d'analyse et de Gestion des Risques Toxicologiques and Institut de Recherche en Santé Publique de l'Université de Montréal (IRSPUM), Faculty of Medicine, Université de Montréal, P.O. Box 6128, Main Station, Montreal, Quebec H3C 3J7, Canada.
authors.forename: Gaétan
authors.initials: G
authors.lastname: Carrier
mesh_terms: D004784:Environmental Monitoring; D004785:Environmental Pollutants / Q000097:blood*; D016021:Epidemiologic Studies; D005260:Female; D006801:Humans; D007231:Infant, Newborn / Q000097:blood; D018811:Maternal Exposure / Q000706:statistics & numerical data*; D011078:Polychlorinated Biphenyls / Q000097:blood*; D011247:Pregnancy / Q000097:blood; D013961:Thyroid Gland / Q000502:physiology*; D013963:Thyroid Hormones / Q000097:blood; D013972:Thyrotropin / Q000097:blood
chemical_list: D004785:Environmental Pollutants; D013963:Thyroid Hormones; D013972:Thyrotropin; D011078:Polychlorinated Biphenyls
keywords: Exposure standardization; Newborns; Polychlorinated biphenyls; Pregnancy; Prenatal exposure; Thyroid hormones