Abstract:

Objective To analyze the iodine nutrition level of key populations in iodine adequate areas surrounding water-borne iodine excess areas in Taiyuan City，provide a basis for scientific and precise iodine supplementation in such areas. Methods In iodine adequate area surrounding water-borne iodine excess area in Taiyuan City from 2020 to 2023，the drinking water samples were collected from residents in each administrative village to test the iodine content in water. Totally 100 children aged 8-10 years old were selected to examine goiter and thyroid nodule by ultrasound B（if the number of participants is insufficient，the age range would be expanded 6-12 years old）. And 50 children and 20 pregnant women（if the number is insufficient，all will be selected） were tested for their household salt iodine and random urine iodine content. Results There were 45 adequate iodine villages surrounding water-borne iodine excess areas in Taiyuan City. A population survey was conducted in 32 iodine adequate villages，the median water iodine content was 76.6 μg/L. Totally 1 941 children were surveyed，the coverage rate of iodized salt was 74.9%，the qualified iodized salt consumption rate was 69.5%，the median urinary iodine concentration was 303.9 μg/L，the goiter rate was 5.9%，and thyroid nodule detection rate was 22.2%. Totally 180 pregnant women were surveyed，the coverage rate of iodized salt was 74.4%，the qualified iodized salt consumption rate was 68.3%，and the median urinary iodine concentration was 178.0 μg/L. Among children in the iodized salt group，the median urinary iodine concentration（317.7 μg/L） was higher than that among children in the non-iodized salt group（281.0 μg/L），the difference was statistically significant（Z=2.046，P<0.01）. The goiter rates in two groups were 6.4% and 4.5% respectively，the thyroid nodule detection rates were 23.8% and 21.1% respectively，and the differences were not statistically significant（χ²=2.039，1.168，both P>0.05）. The analysis was performed based on stratifying water iodine levels（40-<70，70-100 μg/L），the median urinary iodine concentration among children in iodized salt group was 274.1 and 334.8 μg/L，which were higher than those in non-iodized salt group（241.8 and 294.8 μg/L）. When the water iodine content was 40-<70 μg/L，the thyroid nodule detection rate（27.9%） of children from the iodized salt group was higher than that in children from the non-iodized salt group（15.5%），all differences were statistically significant（all P<0.01）.After stratification，the goiter rates of children in two groups were 5.70%，2.70% and 6.70%，5.10%，respectively，and the differences were not statistically significant（χ²=1.564，0.953，both P>0.05）. The median urinary iodine concentrations of pregnant women in the iodized salt group and the non-iodized salt group were 179.0 and 171.0 μg/L. According to the water iodine stratification，the median urinary iodine of pregnant women was in an appropriate state，and the differences were not statistically significant（all P>0.05）. No correlation was observed among the goiter rate or thyroid nodule detection rate in children with salt iodine and water iodine，and no correlation was observed between thyroid nodule detection rate and urine iodine level（all P>0.05）. There was correlation among the goiter rate in children with urine iodine level（r=0.068，P<0.01）. Conclusions The residents in iodine adequate area surrounding water-borne iodine excess area in Taiyuan City primarily consume iodized salt，and the iodine nutrition level of pregnant women is adequate. The children in areas with iodine levels of 40-<70 μg/L，regardless of whether they consume iodized salt or not，have appropriate iodine nutrition. The children in the iodized salt group in areas with iodine levels of 70-100 μg/L have reached iodine excess level. It is recommended to dynamically monitor the iodine content in water and salt，urinary iodine levels in key populations，and thyroid health of children in iodine adequate areas，adjust prevention and control measures in time based on the water iodine content，surrounding environment，and iodine nutrition level of key populations.

Key words: Iodine adequate area, Urinary iodine, Thyroid, Children, Pregnant women