Currently, whether daily excess iodized salt intake increases the risk of thyroid nodules and even thyroid cancer remains controversial. Our research group aimed to provide a theoretical basis for the clinical guidance of daily iodized salt intake and the prevention of thyroid nodules through a retrospective analysis of the correlation between daily iodized salt intake and the risk of thyroid nodules and thyroid cancer in Hunan, China. This study retrospectively analyzed the data of subjects who underwent a physical examination at the Health Management Center, Third Xiangya Hospital of Central South University, between January 1, 2017, and December 31, 2019. Subjects enrolled in this study underwent thyroid ultrasonography and tests to urine routines and liver and kidney function, and all subjects completed a questionnaire survey. The daily iodized salt intake of the study subjects was estimated based on spot urine methods (Tanaka). A multivariate logistic regression model was used to analyze the relationship between daily iodized salt intake and thyroid nodules and thyroid cancer. Among the 51,637 subjects included in this study, the prevalence of thyroid nodules was 40.25%, and the prevalence of thyroid cancer was 0.76%; among all enrolled subjects, only 3.59% had a daily iodized salt intake less than 5 g. In addition, we found that a daily intake of more than 5 g of iodized salt was not only an independent risk factor for the occurrence of thyroid nodules (odds ratio (OR): 2.08, 95% confidence interval (CI): 1.86–2.31, p < 0.001) but also an independent risk factor for the occurrence of thyroid cancer (OR: 5.81, 95% CI: 1.44–23.42, p = 0.012). A pooled analysis showed a significantly higher risk of thyroid nodules in subjects aged > 60 years with a daily iodized salt intake of more than 5 g compared to subjects aged < 60 years with a daily iodized salt intake of no more than 5 g (OR: 4.88, 95% CI: 4.29–5.54, p < 0.001); the risk of thyroid cancer was not significantly different between subjects aged > 60 years with a daily iodized salt intake of more than 5 g and those aged < 60 years with a daily iodized salt intake of no more than 5 g (OR: 2.15, 95% CI: 0.52–8.95, p = 0.281). The risk of thyroid nodules was not increased in physically active subjects with a daily iodized salt intake of more than 5 g compared to physically inactive subjects with a daily iodized salt intake of no more than 5 g (OR: 1.12, 95% CI: 0.97–1.28, p = 0.111). The same protective effect of physical activity was observed for thyroid cancer in subjects whose daily iodized salt intake exceeded 5 g. The risk of thyroid nodules was reduced for subjects with an education level of postgraduate and above, even when the daily iodized salt intake exceeded 5 g, compared to those with high school education and below and a daily iodized salt intake of no more than 5 g (OR: 0.79, 95% CI: 0.66–0.93, p = 0.005); however, a protective effect of education level on the occurrence of thyroid cancer was not observed. Independent risk factors affecting daily iodized salt intake greater than 5 g included age, triglycerides, family history of tumors, physical activity, and marital status. Daily intake of more than 5 g of iodized salt increased the risk of thyroid nodules and thyroid cancer, while increased physical activity and education level reduced the risk of thyroid nodules and thyroid cancer caused by iodized salt intake.

中文翻译：

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高碘盐摄入量与甲状腺结节风险的相关性分析：大型回顾性研究


目前，每日过量摄入碘盐是否会增加甲状腺结节甚至甲状腺癌的风险仍存在争议。本课题组旨在通过回顾性分析湖南省每日碘盐摄入量与甲状腺结节和甲状腺癌风险的相关性，为临床指导每日碘盐摄入量和预防甲状腺结节提供理论依据。本研究回顾性分析了2017年1月1日至2019年12月31日期间在中南大学湘雅三医院健康管理中心进行体检的受试者的数据。本研究入组的受试者均接受了甲状腺超声检查和检查尿常规及肝肾功能，所有受试者均完成问卷调查。研究对象的每日碘盐摄入量是根据点尿法（田中）估算的。采用多因素logistic回归模型分析每日碘盐摄入量与甲状腺结节、甲状腺癌的关系。本研究纳入的51637名受试者中，甲状腺结节患病率为40.25%，甲状腺癌患病率为0.76%；在所有入组受试者中，只有3.59%的人每日碘盐摄入量低于5克。此外，我们发现每日摄入超过5克碘盐不仅是甲状腺结节发生的独立危险因素（优势比（OR）：2.08，95%置信区间（CI）：1.86–2.31） ，p < 0.001）也是甲状腺癌发生的独立危险因素（OR：5.81，95% CI：1.44–23.42，p = 0.012）。 汇总分析显示，与年龄 < 60 岁且每日碘盐摄入量不超过 5 克的受试者相比，年龄 > 60 岁且每日碘盐摄入量超过 5 克的受试者患甲状腺结节的风险显着更高（或： 4.88，95% CI：4.29–5.54，p < 0.001）；年龄 > 60 岁、每日碘盐摄入量超过 5 g 的受试者与年龄 < 60 岁、每日碘盐摄入量不超过 5 g 的受试者之间，甲状腺癌的风险没有显着差异（OR：2.15, 95 % CI：0.52–8.95，p = 0.281）。与每日碘盐摄入量不超过 5 克、体力活动较少的受试者相比，每日碘盐摄入量超过 5 克、体力活动活跃的受试者患甲状腺结节的风险并未增加（OR：1.12，95% CI：0.97） –1.28，p = 0.111）。在每日碘盐摄入量超过 5 克的受试者中，体力活动对甲状腺癌也有同样的保护作用。与高中及以下文化程度、每日碘盐摄入量不超过5克的人群相比，研究生及以上文化程度的受试者，即使每日碘盐摄入量超过5克，甲状腺结节的风险也降低（OR：0.79，95% CI：0.66–0.93，p = 0.005）；然而，没有观察到教育水平对甲状腺癌发生的保护作用。影响每日碘盐摄入量超过 5 克的独立危险因素包括年龄、甘油三酯、肿瘤家族史、体力活动和婚姻状况。每日摄入碘盐超过5克会增加患甲状腺结节和甲状腺癌的风险，而增加体力活动和教育水平会降低因摄入碘盐导致甲状腺结节和甲状腺癌的风险。