1, usually eat iodized salt can prevent thyroid nodules Most thyroid nodules are caused by iodine deficiency, but a long-term high iodine diet can also stimulate thyroid tissue hyperplasia and nodules by promoting elevated levels of thyroid stimulating hormones in the body. Because iodine is already added to salt, long-term consumption of seafood with high iodine content, such as kelp, can also easily cause thyroid nodules. This is related to modern lifestyle, increased night life, increased mental stress, excessive iodized salt intake, and also to the increasing resolution of ultrasound, as lesions of 2-3 mm can now be seen under ultrasound. Only 5%-15% of thyroid nodules are clinically malignant, i.e. thyroid cancer. The determination of benign and malignant thyroid nodules depends on the ultrasound results, which are based on whether the nodules have gravelly calcifications, whether the boundaries are clear, and whether there is abundant blood flow around them. In general, if the following descriptions appear on the ultrasound report: a single nodule, gravelly calcifications within the nodule, or a TIRADS flow grade greater than IV, then a malignant nodule is highly suspected. On the other hand, thyroid nodules that do not show any of the above on ultrasound are usually benign, but it is still necessary to review the thyroid ultrasound in about six months. In addition, the size of the nodule is not a criterion for differentiating benign from malignant, as thyroid cancer of 3 mm to 4 mm is not uncommon in clinical practice. The benignity or malignancy of nodules is not related to the size of nodules, whether the nodules are palpable or not, whether the nodules are single or multiple, or whether the nodules are combined with cystic changes. Most thyroid nodules are harmless and are benign lesions of the thyroid gland, just like a scar or a mole on our skin. However, if the thyroid nodule is a solitary nodule with blood flow grade IV or higher, and if the nodule contains gravel-like calcifications, it is highly likely to become malignant and may evolve into thyroid cancer.