Abstract
Perchlorate, nitrate, and thiocyanate are competitive inhibitors of the sodium iodide symporter of the thyroid membrane. These inhibitors can decrease iodine uptake by the symporter into the thyroid gland and may disrupt thyroid function. This study assesses iodine status and exposure to iodide uptake inhibitors of non-pregnant and non-lactating adult women living in three different cities in Turkey (Istanbul, Isparta and Kayseri). We measured iodine and iodide uptake inhibitors in 24-hr urines collected from study participants (N = 255). All three study populations were mildly iodine deficient, with median urinary iodine (UI) levels of 77.5 µg/L in Istanbul, 58.8 µg/L in Isparta, and 69.8 µg/L in Kayseri. Perchlorate doses were higher in the study population (median 0.13 µg/kg/day), compared with a reference population (median 0.059 µg/kg/day), but lower than the U.S. EPA reference dose (0.7 µg/kg/day). Urinary thiocyanate levels increased with increasing exposure to tobacco smoke, with non-smokers (268 µg/L) significantly lower than light smokers (1110 µg/L), who were significantly lower than heavy smokers (2410 µg/L). This pilot study provides novel data indicating that study participants were moderately iodine deficient and had higher intakes of the iodide uptake inhibitor perchlorate compared with a reference population. Further investigation is needed to characterize the thyroid impact resulting from iodine deficiency coupled with exposure to iodide uptake inhibitors such as perchlorate, thiocyanate and nitrate.
Highlights
Iodine deficiency disorder is a global health problem affecting 740 million people [1]
Mean body mass index (BMI) of all study participants was 26.1 kg/m2, which lies just above the overweight limit according to the World Health Organization [40]
Further analyses find that low iodine intake coupled with concurrent exposure to multiple iodide uptake inhibitors may decrease thyroid function [12,31]
Summary
Iodine deficiency disorder is a global health problem affecting 740 million people [1]. Iodine deficiency causes a broad range of health impacts, including increased perinatal mortality, mental retardation, goiter, hypothyroidism, hyperthyroidism, and retarded physical development [2,3,4]. Iodine is a crucial element for maintaining health by enabling production of adequate levels of thyroid hormone. Thyroid hormone synthesis depends upon adequate iodine levels in the thyroid as a result of the pumping action of the transmembrane protein sodium iodide symporter (NIS). Prolonged inhibition of iodine uptake can lead to decreased thyroid hormone production and could result in hypothyroidism. Combined chronic effects of perchlorate and thiocyanate exposure may cause decreased iodine transport in both the thyroid and the lactating breast, and possibly lead to reduced thyroid function, hypothyroidism and impaired mental and physical development of offspring
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