Thyroid diseases are complex and diverse, with numerous pathogenesis mechanisms. To assist thyroid patients in better health management, urinary iodine testing, as an effective measure, has been continuously validated in clinical applications.

The following text is the original text of "The Significance of Urine Iodine Testing in the Diagnosis and Treatment of Thyroid Nodular Diseases".

In this group of 101 patients with thyroid nodular diseases, there is a significant difference in the male-to-female ratio, with female patients far exceeding male patients. This is because, in addition to iodine factors, female IDD patients also experience increased and periodic changes in thyroid hormone requirements during menstruation, pregnancy, and lactation periods. However, the incidence rate among those under 30 years old is extremely low, indicating that iodine supplementation can significantly reduce the incidence rate of IDD in adolescents. Among thyroid nodular disease patients over 30 years old who have undergone iodine supplementation, those born before iodine supplementation may have iodine deficiency factors, but the vast majority of those who developed the disease after iodine supplementation are suffering from iodine excess, which may be related to abnormal iodine metabolism and excessive iodine intake after long-term iodine deficiency and subsequent iodine supplementation. Therefore, it is not advisable to supplement iodine for individuals with high urinary iodine levels. It has been reported that iodine supplementation cannot achieve therapeutic goals for patients who have already developed nodular thyroid diseases. Another study reported that high iodine feeding in rats with already formed goiter can expand the thyroid follicular area and cause atypical hyperplasia in certain regions, with active proliferation leading to carcinogenesis. Onarany also reported that long-term iodine deficiency-induced benign thyroid diseases can lead to an increase in DNA and aneuploidy in thyroid cells after iodine supplementation, which can result in malignant transformation of benign thyroid tumors. Therefore, it remains to be discussed whether iodine supplementation is beneficial for patients who have already developed thyroid nodular diseases. At least, the surgical indications for thyroid nodular diseases after iodine supplementation should be appropriately broadened, as surgical treatment is the best method for complete cure for such patients.

Multiple versus solitary nodules: Among the 101 cases in this group, 45 were multiple nodules and 56 were solitary nodules. The urinary iodine levels in both groups were significantly higher than those in the normal population. There was no significant correlation between urinary iodine levels and the number of nodules, and the underlying mechanism requires further investigation.

Thyroid function: 2 cases showed elevated thyroid function, but there was no significant difference between the entire group and the normal population. Some people believe that high iodine intake is prone to induce hyperthyroidism, but this has not been proven in this group of cases. The reason may be that many patients with primary hyperthyroidism do not have thyroid nodules.

It has been reported that the increase in urinary iodine after iodine supplementation is related to the changes in thyroid nodular diseases, but there have been no reports on whether there is a direct relationship between urinary iodine and thyroid nodular diseases. In this group, 85.15% of patients with thyroid nodular diseases had urinary iodine levels >300 μg/L, and 57.43% had levels above 2000 μg/L, while the urinary iodine levels of the control group with normal thyroid function were all below 2000 μg/L. Although the measurement of urinary iodine is relatively random due to the many influencing factors, such significant differences also indicate a direct relationship between thyroid nodular diseases and high urinary iodine, and the mechanism needs to be further explored.

This study clarifies that thyroid nodular diseases in Shaoxing area are associated with high urinary iodine levels after iodine supplementation. That is, the pathogenesis of thyroid nodular diseases after iodine supplementation is significantly different from the pathogenesis of iodine deficiency disorders (IDD). Although the mechanism still needs further exploration, it is not advisable to supplement iodine for individuals with high urinary iodine levels. The determination of urinary iodine can help guide iodine supplementation. Abnormally high urinary iodine levels (>2000 μg/L) may indicate the presence of thyroid nodules. The peak incidence of thyroid nodular diseases occurs between the ages of 30 and 60, with a low prevalence rate in individuals under 30 years old. This suggests that iodine supplementation should be implemented dynamically based on different ages, regions, and dietary habits, with urinary iodine levels serving as a specific reference.