Perchlorate and thiocyanate exposure and thyroid function in first-trimester pregnant women

J Clin Endocrinol Metab. 2010 Jul;95(7):3207-15. doi: 10.1210/jc.2010-0014. Epub 2010 Apr 28.


Context: Thyroid hormone, requiring adequate maternal iodine intake, is critical for fetal neurodevelopment. Perchlorate decreases thyroidal iodine uptake by competitively inhibiting the sodium/iodide symporter. It is unclear whether environmental perchlorate exposure adversely affects thyroid function in pregnant women. Thiocyanate, derived from foods and cigarette smoke, is a less potent competitive sodium/iodide symporter inhibitor than perchlorate.

Objective: Our objective was to determine whether environmental perchlorate and/or thiocyanate exposure is associated with alterations in thyroid function in pregnancy.

Design and setting: We conducted a cross-sectional study at health centers in Cardiff, Wales, and Turin, Italy.

Patients: During 2002-2006, 22,000 women at less than 16 wk gestation were enrolled in the Controlled Antenatal Thyroid Screening Study. Subsets of 261 hypothyroid/hypothyroxinemic and 526 euthyroid women from Turin and 374 hypothyroid/hypothyroxinemic and 480 euthyroid women from Cardiff were selected based on availability of stored urine samples and thyroid function data.

Main outcome measures: Urinary iodine, thiocyanate, and perchlorate and serum TSH, free T(4) (FT(4)), and thyroperoxidase antibody were measured.

Results: Urinary iodine was low: median 98 microg/liter in Cardiff and 52 microg/liter in Turin. Urine perchlorate was detectable in all women. The median (range) urinary perchlorate concentration was 5 microg/liter (0.04-168 microg/liter) in Turin and 2 microg/liter (0.02-368 microg/liter) in Cardiff. There were no associations between urine perchlorate concentrations and serum TSH or FT(4) in the individual euthyroid or hypothyroid/hypothyroxinemic cohorts. In multivariable linear analyses, log perchlorate was not a predictor of serum FT(4) or TSH.

Conclusions: Low-level perchlorate exposure is ubiquitous but did not affect thyroid function in this cohort of iodine-deficient pregnant women.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Autoantibodies / immunology
  • Chromatography, Ion Exchange
  • Cross-Sectional Studies
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Health Surveys
  • Humans
  • Immunoassay
  • Iodine / urine
  • Italy
  • Mass Spectrometry
  • Maternal Exposure*
  • Maternal-Fetal Exchange
  • Perchlorates / toxicity*
  • Perchlorates / urine
  • Pregnancy
  • Pregnancy Trimester, First
  • Prospective Studies
  • Regression Analysis
  • Smoking
  • Thiocyanates / toxicity*
  • Thiocyanates / urine
  • Thyroid Function Tests
  • Thyroid Gland / drug effects*
  • Thyroid Gland / immunology
  • Thyrotropin / blood
  • Thyrotropin / immunology
  • Thyroxine / blood
  • Thyroxine / immunology
  • Wales


  • Autoantibodies
  • Perchlorates
  • Thiocyanates
  • Thyrotropin
  • Iodine
  • thiocyanate
  • Thyroxine
  • perchlorate