title: Effects of prenatal exposure to organochlorines on thyroid hormone status in newborns from two remote coastal regions in Québec, Canada.
abstract: BACKGROUND
  Several prospective studies have revealed that prenatal exposure to polychlorinated biphenyls (PCBs) and other organochlorine compounds (OCs) affect neurodevelopment during infancy. One of the mechanisms by which PCBs might interfere with neurodevelopment is a deficit in thyroid hormone (TH) concentrations.
  
  
  OBJECTIVE
  We investigated the potential impact of transplacental exposure to PCBs and hexachlorobenzene (HCB) on TH concentrations in neonates from two remote coastal populations exposed to OCs through the consumption of seafood products.
  
  
  METHODS
  Blood samples were collected at birth from the umbilical cord of neonates from Nunavik (n=410) and the Lower North Shore of the St. Lawrence River (n=260) (Québec, Canada) for thyroid parameters [thyroid-stimulating hormone (TSH), free T4 (fT4), total T3 (tT3), and thyroxine-binding globuline (TBG)] and contaminants analyses.
  
  
  RESULTS
  In multivariate models, umbilical cord plasma concentrations of PCB 153, the predominant PCB congener, were not associated with TH and TSH levels in both populations. Prenatal exposure to HCB was positively associated with fT4 levels at birth in both populations (Nunavik, beta=0.12, p=0.04; St. Lawrence, beta=0.19, p<0.01), whereas TBG concentrations were negatively associated with PCB 153 concentrations (beta=-0.13, p=0.05) in the St. Lawrence cohort.
  
  
  CONCLUSIONS
  OCs levels were not associated to a reduction in THs in neonates from our two populations. Essential nutrients derived from seafood such as iodine may have prevented the negative effects of OCs on the thyroid economy during fetal development.
authors.affiliation: Public Health Research Unit, Laval University Medical Research Centre-Centre Hospitalier, Universitaire de Québec, Québec City, Québec, Canada.
authors.forename: Renée
authors.initials: R
authors.lastname: Dallaire
authors.forename: Eric
authors.initials: E
authors.lastname: Dewailly
authors.forename: Pierre
authors.initials: P
authors.lastname: Ayotte
authors.forename: Gina
authors.initials: G
authors.lastname: Muckle
authors.forename: Claire
authors.initials: C
authors.lastname: Laliberté
authors.forename: Suzanne
authors.initials: S
authors.lastname: Bruneau
mesh_terms: D004785:Environmental Pollutants / Q000097:blood / Q000378:metabolism*; D005260:Female; D006801:Humans; D006843:Hydrocarbons, Chlorinated / Q000097:blood / Q000378:metabolism*; D007231:Infant, Newborn; D018811:Maternal Exposure / Q000706:statistics & numerical data*; D008954:Models, Biological; D011792:Quebec; D013963:Thyroid Hormones / Q000097:blood / Q000378:metabolism*
chemical_list: D004785:Environmental Pollutants; D006843:Hydrocarbons, Chlorinated; D013963:Thyroid Hormones