Iodine Nutritional Status and Related Factors among Chinese School-Age Children in Three Different Areas: A Cross-Sectional Study

Abstract

We evaluated the iodine nutritional status and related factors among school-age children based on the 2016 National Nutrition and Health Surveillance of Children and Lactating Women; 3808 children from Hebei, Guangxi, and Zhejiang province were included in the study. Urinary iodine concentration (UIC), thyroid-stimulating hormone (TSH), body mass index (BMI), vitamin A (VA), and vitamin D (VD) were measured. The abnormal rate of UIC and TSH were assessed. Relationships between UIC/TSH and the possible factors were analyzed. The overall median UIC was 185.14 µg/L, and the median UIC of children aged 8–10 was 164.60 µg/L. Prevalence of iodine deficiency and excess was 13.84% and 14.36%, respectively, and 12.87% of children showed TSH excess. UIC, as well as the abnormal rates of iodine deficiency (ID) and TSH, were significantly different among the three provinces. The median UICs and excess rates increased with age, reaching 211.45 µg/L and 21.35% at age of 14~, while TSH showed the opposite trend. Overweight children tended to have lower UIC and higher TSH. Higher UIC and TSH were found in VA sufficient group (p < 0.01). Further, the VD deficient group had a higher TSH compared to the sufficient group (p < 0.01). Moreover, UI and TSH distribution was obviously different among different vitamin A/D status (p < 0.05). Although the median UIC of school-age children was optimal, there were pockets of inadequate and excessive UI in the three provinces. Compared to the national IDD monitoring results in 2014, the iodine nutritional status of children was greatly improved. Considerations of region, age, BMI, VA, or VD are needed in the future iodine evaluation and surveillance.

Iodine Nutrition and Related Factors of Mothers with Children under 2 Years Old from Three Different Areas in China: A Cross-sectional Survey

“…And iodine de ciency can accelerate lipolysis and fatty acid oxidation, and increase plasma TSH level without affecting thyroid hormone signal [30]. Our previous study on school-age children has also con rmed this phenomenon [9]. But obese mothers in this study showed higher MUIC, which was consistent with a Mexican study conducted in children from primary schools, nding a positive correlation between UIC values and BMI, and the prevalence of overweight and obesity [31].…”

“…Since geographic in uences on the iodine status existed in pregnant and lactating women, neonates, and school-age children [26,27], and geographic locations with poor iodine status were suggested to identify [17], we then analyzed UIC differences among the three representative provinces. Our previous study concluded that the iodine nutritional status of school-age children varied among Hebei, Zhejiang and Guangxi, and lower MUIC and higher proportion of UIC < 100 µg/L was observed in Hebei and Zhejiang [9]. Similar to school children, the MUIC of mothers in Zhejiang was the lowest and the proportion of UIC < 100 µg/L in Zhejiang was the highest.…”

“…We guess that dietary patterns, lifestyles and iodised salt intake may be the major factors which in uence the iodine nutritional status for rural and urban mothers. As UIC was shown to be positively related to age among children, and prevalence of UIC < 100 µg/L was the highest among the youngest children, which might be related to lower iodine intake [9], we then analyzed the effect of age on UIC among mothers. In this study, UIC was not statistically signi cant among the agegroups, but we also found that the younger group was more prone to having UIC < 50 µg/L.…”

“…For example, a signi cant association between VDD and high prevalence of thyroid autoimmunity and dysfunction in participants with excessive iodine intake was found in the Korean population [12]. And our previous study showed the iodine nutritional status of children and adolescents was related to VA and VD [9]. It is also necessary to analyze the relationship between iodine nutritional status and VA/VD in mothers with children under 2 years old.…”

“…According to the 2014 monitoring data of IDD in China, the overall level of urinary iodine in the eastern region was lower than that in the central and western regions [7]. As Hebei, Zhejiang, Guangxi in eastern China were historically areas with cretinism and low iodized-salt coverage rates [8], we previously assessed the iodine nutritional status among school-age children in the three representative provinces, which showed that lower MUIC and higher proportion of < 100 µg/L was observed in Hebei and Zhejiang, compared to Guangxi [9]. So similar study is warranted among mothers with children under 2 years old.…”