Thyroid antagonists and thyroid indicators in U.S. pregnant women in the Vanguard Study of the National Children's Study.

The sodium iodide-symporter (NIS) mediates uptake of iodide into thyroid follicular cells. This key step in thyroid hormone synthesis is inhibited by perchlorate, thiocyanate (SCN) and nitrate (NO3) anions. When these exposures occur during pregnancy the resulting decreases in thyroid hormones may adversely affect neurodevelopment of the human fetus. Our objectives were to describe and examine the relationship of these anions to the serum thyroid indicators, thyroid stimulating hormone (TSH) and free thyroxine (FT4), in third trimester women from the initial Vanguard Study of the National Children's Study (NCS); and to compare urine perchlorate results with those in pregnant women from the National Health and Nutritional Examination Survey (NHANES). Urinary perchlorate, SCN, NO3, and iodine, serum TSH, FT4, and cotinine were measured and a food frequency questionnaire (FFQ) was administered to pregnant women enrolled in the initial Vanguard Study. We used multiple regression models of FT4 and TSH that included perchlorate equivalent concentration (PEC, which estimates combined inhibitory effects of the anions perchlorate, SCN, and NO3 on the NIS). We used multiple regression to model predictors of each urinary anion, using FFQ results, drinking water source, season of year, smoking status, and demographic characteristics. Descriptive statistics were calculated for pregnant women in NHANES 2001-2012. The geometric mean (GM) for urinary perchlorate was 4.04µg/L, for TSH 1.46mIU/L, and the arithmetic mean for FT4 1.11ng/dL in 359 NCS women. In 330 women with completed FFQs, consumption of leafy greens, winter season, and Hispanic ethnicity were significant predictors of higher urinary perchlorate, which differed significantly by study site and primary drinking water source, and bottled water was associated with higher urinary perchlorate compared to filtered tap water. Leafy greens consumption was associated with higher urinary NO3 and higher urinary SCN. There was no association between urinary perchlorate or PEC and TSH or FT4, even for women with urinary iodine <100µg/L. GM urinary perchlorate concentrations in the full sample (n=494) of third trimester NCS women (4.03µg/L) were similar to pregnant women in NHANES (3.58µg/L).

Mortensen ME ，Birch R ，Wong LY ，Valentin-Blasini L ，Boyle EB ，Caldwell KL ，Merrill LS ，Moye J Jr ，Blount BC ... -  《-》

The effects of perchlorate, nitrate, and thiocyanate on free thyroxine for potentially sensitive subpopulations of the 2001-2002 and 2007-2008 National Health and Nutrition Examination Surveys.

Suh M ，Abraham L ，Hixon JG ，Proctor DM ... -  《-》

Environmental perchlorate and thiocyanate exposures and infant serum thyroid function.

Leung AM ，Braverman LE ，He X ，Schuller KE ，Roussilhes A ，Jahreis KA ，Pearce EN ... -  《-》

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

Thyroid hormone, requiring adequate maternal iodine intake, is critical for neurodevelopment in utero. Perchlorate and, less so, thiocyanate decrease uptake of iodine into the thyroid gland by competitively inhibiting the sodium/iodide symporter (NIS). It remains unclear whether environmental perchlorate exposure adversely affects thyroid function in first-trimester pregnant women. Cross-sectional. 134 pregnant women from Athens, Greece, at mean ± SD 10·9 ± 2·3 weeks' gestation. Urinary iodide, perchlorate, and thiocyanate and thyroid function tests were measured. The median urinary iodide was 120 μg/l. Urinary perchlorate levels were detectable in all women: median (range) 4·1 (0·2-118·5) μg/l. Serum thyroperoxidase antibodies (TPO Ab) were detectable in 16% of women. Using Spearman's rank correlation analyses, there was no correlation between urinary perchlorate concentrations and serum TSH, although inverse correlations were seen between urine perchlorate and free T3 and free T4 values. In univariate analyses, urine thiocyanate was positively correlated with serum TSH, but was not associated with serum free T3 or free T4. Urine perchlorate was positively correlated with gestational age. In multivariate analyses adjusting for urinary iodide concentrations, urine thiocyanate, gestational age, maternal age and TPO Ab titres, urine perchlorate was not a significant predictor of thyroid function. Low-level perchlorate and thiocyanate exposure is ubiquitous, but, in adjusted analyses, is not associated with alterations in thyroid function tests among mildly iodine-deficient Greek women in the first trimester of pregnancy.

Pearce EN ，Alexiou M ，Koukkou E ，Braverman LE ，He X ，Ilias I ，Alevizaki M ，Markou KB ... -  《-》

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

Pearce EN ，Lazarus JH ，Smyth PP ，He X ，Dall'amico D ，Parkes AB ，Burns R ，Smith DF ，Maina A ，Bestwick JP ，Jooman M ，Leung AM ，Braverman LE ... -  《-》