title: Environmental perchlorate and thiocyanate exposures and infant serum thyroid function.
abstract: BACKGROUND
  Breastfed infants rely on maternal iodine for thyroid hormone production required for neurodevelopment. Dietary iodine among women of childbearing age in the United States may be insufficient. Perchlorate (competitive inhibitor of the sodium/iodide symporter [NIS]) exposure is ubiquitous. Thiocyanate, from cigarettes and diet, is a weaker NIS inhibitor. Environmental perchlorate and thiocyanate exposures could decrease breast milk iodine by competitively inhibiting NIS in lactating breasts (thus impairing infants' iodine availability), and/or infants' thyroidal NIS to directly decrease infant thyroid function. The current study assessed the relationships between environmental perchlorate and thiocyanate exposures and infant serum thyroid function.
  
  
  METHODS
  Iodine, perchlorate, and thiocyanate in breast milk, maternal and infant urine, and infant serum thyroid function tests were cross-sectionally measured in Boston-area women and their 1-3 month-old breastfed infants. Univariate and multivariable analyses assessed relationships between iodine, perchlorate, thiocyanate, thyroid-stimulating hormone (TSH), and free thyroxine (FT4) levels.
  
  
  RESULTS
  In 64 mothers and infants, median (range) iodine levels were 45.6 μg/L (4.3-1080) in breast milk, 101.9 μg/L (27-570) in maternal urine, and 197.5 μg/L (40-785) in infant urine. Median perchlorate concentrations were 4.4 μg/L (0.5-29.5) in breast milk, 3.1 μg/L (0.2-22.4) in maternal urine, and 4.7 μg/L (0.3-25.3) in infant urine. There were no correlations between infant TSH or FT4 and iodine, perchlorate, and thiocyanate levels in breast milk, maternal urine, and infant urine. In multivariable analyses, perchlorate and thiocyanate levels in breast milk, maternal urine, and infant urine were not significant predictors of infant TSH or FT4.
  
  
  CONCLUSIONS
  Boston-area mothers and their breastfed infants are generally iodine sufficient. Although environmental perchlorate and thiocyanate are ubiquitous, these results do not support the concern that maternal and infant environmental perchlorate and thiocyanate exposures affect infant thyroid function.
authors: Section of Endocrinology, Diabetes, and Nutrition, Boston University School of Medicine, 88 East Newton St., Boston, MA 02118, USA. angela.leung@bmc.org
authors: Angela M
authors: AM
authors: Leung
authors: Lewis E
authors: LE
authors: Braverman
authors: Xuemei
authors: X
authors: He
authors: Kristin E
authors: KE
authors: Schuller
authors: Alexandra
authors: A
authors: Roussilhes
authors: Katherine A
authors: KA
authors: Jahreis
authors: Elizabeth N
authors: EN
authors: Pearce
mesh_terms: D000328:Adult; D001900:Boston; D001942:Breast Feeding; D003430:Cross-Sectional Studies; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D007223:Infant; D007455:Iodine / Q000032:analysis / Q000652:urine; D008895:Milk, Human / Q000737:chemistry*; D010472:Perchlorates / Q000009:adverse effects* / Q000032:analysis / Q000652:urine; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000139:chemically induced*; D013861:Thiocyanates / Q000009:adverse effects* / Q000032:analysis / Q000652:urine; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000737:chemistry / Q000378:metabolism; D013972:Thyrotropin / Q000097:blood / Q000652:urine; D013974:Thyroxine / Q000032:analysis / Q000097:blood / Q000652:urine; D055815:Young Adult
chemical_list: D010472:Perchlorates; D013861:Thiocyanates; D013972:Thyrotropin; D007455:Iodine; C031760:thiocyanate; D013974:Thyroxine; C494474:perchlorate