Thyroid Antagonists (Perchlorate, Thiocyanate, and Nitrate) and Childhood Growth in a Longitudinal Study of U.S. Girls

BACKGROUND Perchlorate, thiocyanate, and nitrate are sodium/iodide symporter (NIS) inhibitors that block iodide uptake into the thyroid, thus affecting thyroid function. Thyroid dysfunction can adversely affect somatic growth and development in children. To our knowledge, no studies have examined effects of NIS inhibitors on body size measures. OBJECTIVE We investigated associations between NIS inhibitors and childhood growth in 940 girls from the Puberty Study of the Breast Cancer and Environment Research Program. METHODS Urine samples collected from girls 6-8 years of age at enrollment (2004-2007) from New York City, greater Cincinnati, Ohio, and the Bay Area in California were analyzed for NIS inhibitors and creatinine (C). The longitudinal association between NIS inhibitors and anthropometric measures [height, waist circumference, and body mass index (BMI)] during at least three visits was examined using mixed effects linear models, adjusted for race and site. RESULTS Compared with girls in the low-exposure group (3.6, 626, and 500 mg/gC, median perchlorate, thiocyanate, and nitrate, respectively) girls with the highest NIS inhibitor exposure (9.6, 2,343, and 955 mg/gC, median perchlorate, thiocyanate, and nitrate, respectively) had slower growth in waist circumference and BMI but not height. Significant differences in the predicted mean waist circumference and BMI between the low- and high-exposure groups were observed beginning at 11 years of age. CONCLUSIONS Higher NIS inhibitor exposure biomarkers were associated with reductions in waist circumference and BMI. These findings underscore the need to assess exposure to NIS inhibitors with respect to their influence on childhood growth. CITATION Mervish NA, Pajak A, Teitelbaum SL, Pinney SM, Windham GC, Kushi LH, Biro FM, Valentin-Blasini L, Blount BC, Wolff MS, for the Breast Cancer and Environment Research Project (BCERP). 2016. Thyroid antagonists (perchlorate, thiocyanate, and nitrate) and childhood growth in a longitudinal study of U.S. girls. Environ Health Perspect 124:542-549; http://dx.doi.org/10.1289/ehp.1409309.