To investigate the iodine nutritional status of children in Qingdao City and the effects of prevention and treatment measures on iodine deficiency disorders (IDD), and to provide a scientific basis for guiding residents to scientifically supplement iodine, taking timely targeted prevention and control measures, and scientifically adjusting intervention strategies.

According to "National Iodine Deficiency Disorders Surveillance Program (2016 edition)" and "Iodine Deficiency Disorders Surveillance Program of Shandong Province", from 2018 to 2020, using the cluster sampling method, children aged 8-10 years in Qingdao City were chosen to test their household salt iodine content and random urinary iodine content, and to examine their thyroid volume by B-ultrasonography, and the correlation between thyroid volume and physical development indexes was analyzed.

From 2018 to 2020, a total of 6 057 children were monitored, including 3 068 boys and 2 989 girls. The median of salt iodine and iodized salt iodine of children was 23.50 and 24.10 mg/kg. The qualified rate of iodized salt was 89.95% (4 832/5 372), the coverage rate of iodized salt was 88.69% (5 372/6 057), and the consumption rate of qualified iodized salt was 79.78% (4 832/6 057). There were significant differences in the qualified rate of iodized salt, the coverage rate of iodized salt and the consumption rate of qualified iodized salt between different years (χ² = 135.26, 314.71, 342.87, P < 0.001). A total of 6 057 urine samples were collected from children, and the median of urinary iodine was 193.92 μg/L, of which 16.2% (979/6 057) were < 100 μg/L, and 22.5% (1 361/6 057) were ≥300 μg/L. There were statistically significant differences in the medians of urinary iodine between different years, gender and whether eating iodized salt (H/Z = 37.25,-3.89,-5.69, P < 0.001), the median of urinary iodine in boys was higher than that of girls, and the median of urinary iodine in eating iodized salt group was higher than that of eating non-iodized salt group. There was no significant difference in the median of urinary iodine between different age (H = 4.33, P = 0.119). The rate of goiter in children was 3.45% (71/2 057), and the difference between different years was statistically significant (χ² = 42.68, P < 0.001). The incidence of goiter in 2020 [7.31% (45/616)] was significantly higher than that in 2018 and 2019 [2.81% (18/641), 1.00% (8/800), P < 0.001]. Thyroid volume of children was positively correlated with height and weight (r = 0.20, 0.22, P < 0.001).

The iodine nutritional level of children aged 8-10 years in Qingdao City is appropriate. However, the incidence of goiter in children in some years is relatively high. The qualified rate of iodized salt, the coverage rate of iodized salt and the consumption rate of qualified iodized salt are all lower than the national standard for elimination of IDD, which should be paid attention to.

Iodine; Deficiency diseases; Urinary iodine; Salt iodine