title: CO-occurring exposure to perchlorate, nitrate and thiocyanate alters thyroid function in healthy pregnant women.
abstract: BACKGROUND
  Adequate maternal thyroid function during pregnancy is necessary for normal fetal brain development, making pregnancy a critical window of vulnerability to thyroid disrupting insults. Sodium/iodide symporter (NIS) inhibitors, namely perchlorate, nitrate, and thiocyanate, have been shown individually to competitively inhibit uptake of iodine by the thyroid. Several epidemiologic studies examined the association between these individual exposures and thyroid function. Few studies have examined the effect of this chemical mixture on thyroid function during pregnancy
  
  
  OBJECTIVE
  We examined the cross sectional association between urinary perchlorate, thiocyanate and nitrate concentrations and thyroid function among healthy pregnant women living in New York City using weighted quantile sum (WQS) regression.
  
  
  METHODS
  We measured thyroid stimulating hormone (TSH) and free thyroxine (FreeT4) in blood samples; perchlorate, thiocyanate, nitrate and iodide in urine samples collected from 284 pregnant women at 12 (±2.8) weeks gestation. We examined associations between urinary analyte concentrations and TSH or FreeT4 using linear regression or WQS adjusting for gestational age, urinary iodide and creatinine.
  
  
  RESULTS
  Individual analyte concentrations in urine were significantly correlated (Spearman's r 0.4-0.5, p<0.001). Linear regression analyses did not suggest associations between individual concentrations and thyroid function. The WQS revealed a significant positive association between the weighted sum of urinary concentrations of the three analytes and increased TSH. Perchlorate had the largest weight in the index, indicating the largest contribution to the WQS.
  
  
  CONCLUSIONS
  Co-exposure to perchlorate, nitrate and thiocyanate may alter maternal thyroid function, specifically TSH, during pregnancy.
authors.affiliation: Department of Preventive Medicine, Icahn School of Medicine, New York, New York. Electronic address: megan.horton@mssm.edu.
authors.forename: Megan K
authors.initials: MK
authors.lastname: Horton
authors.affiliation: National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Benjamin C
authors.initials: BC
authors.lastname: Blount
authors.affiliation: National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Liza
authors.initials: L
authors.lastname: Valentin-Blasini
authors.affiliation: Department of Obstetrics and Gynecology, Columbia University, New York, New York.
authors.forename: Ronald
authors.initials: R
authors.lastname: Wapner
authors.affiliation: Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York.
authors.forename: Robin
authors.initials: R
authors.lastname: Whyatt
authors.affiliation: Department of Preventive Medicine, Icahn School of Medicine, New York, New York.
authors.forename: Chris
authors.initials: C
authors.lastname: Gennings
authors.affiliation: Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York.
authors.forename: Pam
authors.initials: P
authors.lastname: Factor-Litvak
mesh_terms: D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D052244:Endocrine Disruptors / Q000633:toxicity / Q000652:urine*; D005260:Female; D006801:Humans; D007455:Iodine / Q000652:urine; D016014:Linear Models; D018811:Maternal Exposure / Q000009:adverse effects*; D009519:New York City; D009566:Nitrates / Q000633:toxicity / Q000652:urine*; D010472:Perchlorates / Q000633:toxicity / Q000652:urine*; D011247:Pregnancy; D013861:Thiocyanates / Q000633:toxicity / Q000652:urine*; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000187:drug effects* / Q000503:physiopathology; D013963:Thyroid Hormones / Q000097:blood; D055815:Young Adult
chemical_list: D052244:Endocrine Disruptors; D009566:Nitrates; D010472:Perchlorates; D013861:Thiocyanates; D013963:Thyroid Hormones; D007455:Iodine; C494474:perchlorate
keywords: Chemical mixtures; Perchlorate; Pregnancy; Thyroid function