title: Polychlorinated biphenyl exposure and deiodinase activity in young infants.
abstract: BACKGROUND
  Several studies have shown effects of polychlorinated biphenyls (PCBs) on serum thyroid hormone levels in pregnant woman and their infants, while other studies did not find such effects. How PCBs might affect thyroid hormone metabolism, is still unclear. Potential mechanisms are direct influence on the thyroid gland, binding to thyroid binding proteins, increased excretion or metabolism of thyroid hormones by deiodinases or sulfatases. It is also not well known whether the effect on thyroid hormone levels is caused by PCBs themselves, or by their hydroxylated metabolites (OH-PCBs).
  
  
  OBJECTIVE
  To determine the effects of perinatal exposure to PCBs and OH-PCBs on thyroid hormone levels in cord blood and in serum of newborn infants.
  
  
  METHODS
  In a Dutch cohort of 100 mother-infant pairs, exposed to background PCB levels, correlations were assessed between 10 PCBs and 6 OH-PCBs in maternal blood during pregnancy and serum thyroxine (T4), T4 sulfate (T4S), triiodothyronine (T3), reverse T3 (rT3), thyroid-stimulating hormone (TSH) and thyroxine-binding globulin (TBG) levels in cord blood and in serum of three- and 18-month-old infants. We corrected for age of the mother, gestational age, gender and type of feeding.
  
  
  RESULTS
  After correction, prenatal levels of three of 10 measured PCBs showed a positive correlation with cord serum T3, and four PCBs showed a negative correlation with cord serum rT3. After correction, two PCBs and the sum of the 10 measured PCBs were positively correlated with the cord serum T3/rT3 ratio, an indicator of deiodinase 3 activity. No correlations were found between PCBs and T4, TSH and TBG in cord blood. 4-OH-PCB-107 was correlated with T4 at 3months and T4, T4S and T3 at 18months.
  
  
  CONCLUSIONS
  Our results suggest that PCBs have a negative effect on deiodinase type 3 activity, as reflected by a positive correlation with the T3/rT3 ratio. We identified a potential mechanism by which PCBs may affect thyroid hormone metabolism during human development.
authors.affiliation: Division of Neonatology, Department of Pediatrics, Beatrix Children's Hospital, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Shalini D
authors.initials: SD
authors.lastname: Soechitram
authors.affiliation: Division of Neonatology, Department of Pediatrics, Beatrix Children's Hospital, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands. Electronic address: s.a.berghuis@umcg.nl.
authors.forename: Sietske A
authors.initials: SA
authors.lastname: Berghuis
authors.affiliation: Department of Internal Medicine, Erasmus Medical Centre, Rotterdam, The Netherlands.
authors.forename: Theo J
authors.initials: TJ
authors.lastname: Visser
authors.affiliation: Division of Neonatology, Department of Pediatrics, Beatrix Children's Hospital, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Pieter J J
authors.initials: PJJ
authors.lastname: Sauer
mesh_terms: D005260:Female; D005312:Fetal Blood; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007453:Iodide Peroxidase / Q000378:metabolism*; D018811:Maternal Exposure / Q000009:adverse effects*; D009426:Netherlands; D011078:Polychlorinated Biphenyls / Q000009:adverse effects*; D011247:Pregnancy; D013963:Thyroid Hormones / Q000097:blood; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D056825:Thyroxine-Binding Globulin / Q000032:analysis; D014284:Triiodothyronine / Q000097:blood
chemical_list: D013963:Thyroid Hormones; D056825:Thyroxine-Binding Globulin; D014284:Triiodothyronine; D013972:Thyrotropin; D011078:Polychlorinated Biphenyls; D007453:Iodide Peroxidase; D013974:Thyroxine
keywords: Deiodinase activity; Modes of action; PCB; Persistent organic pollutant; Prenatal exposure; Thyroid hormone