Exposures to perchlorate could reduce thyroidal iodine uptake in women and fetuses

Exposures to perchlorate (ClO4), a compound found at low levels in the environment, and thiocyanate (SCN), a compound found in cigarette smoke and some foods, is unlikely to alter thyroid function in pregnant women and fetuses, according to new data presented at the 82nd Annual Meeting of the American Thyroid Association (ATA) in Québec City, Québec, Canada.

"The developing fetus is reliant on maternal iodine for thyroid hormone production for normal neurodevelopment. Environmental exposures to ClO4 and SCN exposures during pregnancy could potentially decrease thyroidal iodine uptake in the mother and/or her fetus and subsequent thyroid hormone synthesis," said Elizabeth Pearce, MD, of Boston Medical Center, Program Co-Chair of the ATA Annual Meeting and co-author of the study.

Led by Angela Leung at the Boston University School of Medicine in Boston, Mass., a team of researchers thus sought to determine for the first time the urinary CIO4 and SCN concentrations in Canada. They recruited 150 pregnant women from four low-risk antenatal outpatient clinics in Toronto, Canada, to provide a spot urine sample for the measurement of both compounds. The women were in their second and third trimesters, primarily Caucasian, well educated, and relatively affluent. The median urinary CIO4 concentration was 3.2 lg/L (range, 0.5-48.1 lg/L), and the median urinary SCN concentration was 351lg/L (range, 28-1195lg/L). These women were iodine sufficient (median urinary iodine concentration 227.1lg/L), as was previously presented at the 2011 American Thyroid Association meeting.

Researchers noted that low levels of both CIO4 and SCN are comparable to those previously reported by in iodine-deficient and sufficient pregnant women from Wales, Italy, Argentina, and the United States where environmental exposures had no effect on maternal thyroid function.