Background:To eliminate the harm induced by iodine deficiency, a strategy of universal salt iodization (USI) is adopted. During this period, it shows a significant increasing trend in the prevalence of thyroid nodules, resulting in shining a spotlight on whether thyroid nodules are related to the level of iodine nutrition. In this study, a 1:1 matched case-control study is conducted to investigate whether thyroid nodules are related to the level of iodine nutrition and whether there are differences in thyroid function indicators. And other influencing factors of thyroid nodules are further explored. Methods:Villages with median urinary iodine (MUI) <100μg/L, 100-199μg/L, and 200-299μg/L in general population were selected as the survey sites. The residents who have lived there for more than 5 years with thyroid nodules tested by B-ultrasound were the case group, while those without nodules found by B-ultrasound examination were the control group that matched 1:1 with the case group by age (±3 years), gender and region. All subjects completed questionnaires, collected blood and urine samples to detect the thyroid function indicators and urinary iodine concentration. Results: There was no statistically significant difference in the MUI between the case group and the control group in the areas with adequate iodine intake, the areas with mild iodine deficiency(P>0.05); The MUI of the case group in the areas where iodine intake was more than adequate was lower than that of the control group(P<0.05); The case group’s levels of Tg and FT4 in both areas with mild iodine deficiency and more than adequate iodine intake were higher than those of the control group, whereas only the level of Tg of the case group was higher than that of the control group in the areas with adequate iodine intake, meaning that the difference was statistically significant (P<0.05); Other indicators had no statistical significance. The conditional Logistic regression model fitted by Enter method resulted that there were statistically significant correlations between history of thyroid disorders, Tg, TgAb and thyroid nodules. Conclusions: On the one hand, there was no statistical correlation between the iodine nutrition and thyroid nodules in the areas with adequate iodine intake and areas with mild iodine deficiency. On the other hand, in the areas with more than adequate iodine intake, the urine iodine concentration in the nodule group was lower than that in the non-nodule group, which indicates that when the urine iodine concentration is 200-299 μg/L, a slight increase in urinary iodine may help inhibit the occurrence of nodules. History of thyroid disorders and increased Tg and TgAb levels were risk factors for thyroid nodules. Tg can serve as a functional biomarker for thyroid nodules.

Objective: Iodine deficiency and excessive salt intake have adverse health effects. This study evaluated the iodine level and salt intake in Chinese adults after implementing the salt reduction program and compared both with the World Health Organization (WHO) recommendations. Methods：Adults aged 18–59 years were randomly selected using multi-stage stratified random sampling in Fujian Province, China. Iodine, sodium, and creatinine concentrations in spot urine samples were measured. Knudsen equation was used to determine 24-h urinary iodine and sodium excretion. Results: The median urinary iodine concentration (mUIC) among adults (n = 3513) was 132.0 μg/L. No significant differences were observed in mUIC between sexes and age groups (P > 0.05). The median daily salt intake (DSI) among Chinese adults was 10.2 g/d, and only <13.6% of the population met the recommended WHO upper DSI level of 5 g/d. The DSI of residents was higher in the noncoastal rural areas than in the other three areas (P < 0.05). The adults aged 45–59 years consumed more salt compared with those aged 18–49 years (P < 0.05). The logistic regression demonstrated that the people living in coastal and noncoastal urban areas consumed less salt compared with those in noncoastal rural areas. Except for noncoastal urban areas, the daily iodine intake was lower (<150 μg/d) among women of childbearing age in the low–salt intake group (<5 g/d) (P < 0.05) compared with the high–salt intake group (≥5 g/d). Conclusions：Iodine nutrition in Chinese adults was sufficient, but the salt intake was substantially higher than the WHO recommendations. Further policy implementation is needed to reduce salt intake and improve the monitoring of iodine levels in Chinese adults, especially in women of childbearing age.

Background A significant increasing trend in the prevalence of thyroid nodules has resulted in shining a spotlight on whether thyroid nodules are related to the level of iodine nutrition. In this study, a 1:1 matched case-control study is conducted to investigate whether thyroid nodules are related to the level of iodine nutrition.Methods Selected three survey sites with median urinary iodine (MUI) < 100µg/L, 100–199µg/L, and 200–299µg/L. The residents who have lived there for at least 5 years with thyroid nodules were the case group, while those without nodules were the control group that matched 1:1 with the case group by age (± 3 years), gender and region. All subjects completed questionnaires, collected blood and urine samples.Results The MUI of the case group in the areas with more than adequate iodine intake was lower than that of the control group(P < 0.05); Only the level of Tg of the case group was higher than that of the control group in the areas with adequate iodine intake(P < 0.05).The conditional Logistic regression model resulted that there were statistically significant correlations between history of thyroid disorders, Tg, TgAb and thyroid nodules.Conclusions When in the areas with more than adequate iodine intake, a slight increase in urinary iodine may help inhibit the occurrence of nodules. History of thyroid disorders, increased Tg and TgAb levels were risk factors for thyroid nodules. Tg can serve as a functional biomarker for thyroid nodules.