1. What is a thyroid nodule? A lump in the thyroid gland is collectively called a thyroid nodule and is the most common type of thyroid disorder. Nodules are found by palpation in about 3-7% of cases, while ultrasonography can reveal nodules in 20-76% of subjects. They are more common in women than in men (4:1) and more common in middle-aged and older people than in teenagers. In fact, nodules are just a morphological description of thyroid swellings caused by tumors, cysts, inflammatory masses or other diseases. There are benign and malignant thyroid nodules without specific clinical manifestations. Therefore, the nature of a thyroid nodule cannot be determined by physical examination or ultrasound alone, but requires a combination of medical history, physical examination, laboratory tests, and even pathological examination. Of course, objectively speaking, the vast majority of thyroid nodules are benign, with malignancy accounting for only 5%. And even malignant thyroid nodules are much less aggressive than lung cancer. Therefore, once a nodule is found, there is no need to panic. 2.What are the causes of thyroid nodules? The etiology of thyroid nodules is complex and is currently believed to be related to radiation exposure, autoimmunity, genetics, iodine intake and other factors. History of radiation exposure is an important causative factor for thyroid cancer. Individuals who received radiation doses of 10-1000 rad during childhood have a higher incidence of thyroid cancer. Patients with autoimmune thyroiditis are prone to develop thyroid nodules. There is no evidence that other thyroid cancers are hereditary, except for familial medullary carcinoma, and only about 7% of patients with papillary thyroid cancer may have a familial predisposition. Severe iodine deficiency and excessive iodine intake can both cause thyroid nodules. 3.How to diagnose thyroid nodules? Ultrasound has ideal resolution and can detect tiny nodules as small as 2mm in diameter, which improves the sensitivity of thyroid nodule detection. It can also be used to follow the growth of the nodule. 4. What should I do if I find a thyroid nodule? The best way to distinguish between benign and malignant thyroid nodules is ultrasound-guided fine-needle aspiration cytology (FNA) of the thyroid nodules. However, FNA cannot be performed on all patients with thyroid nodules. FNA is mainly performed on nodules ≥1 cm in diameter and nodules that are not very large but have the following conditions: ① previous radiation therapy to the head and neck; ② family history of medullary thyroid carcinoma or multiple endocrine tumors type II; ③ age <20 or >70 years; ④ male; ⑤ fast growing nodules; ⑥ hard nodules with indistinct margins; ⑦ nodules that are ⑦ nodules; ⑧ enlarged cervical lymph nodes; ⑨ hoarseness, cough, dysphagia, dyspnea, etc. For nodules smaller than 1 cm, follow-up ultrasound can be performed every 3-6 months. If nodules are found to be rapidly increasing in size, or if malignant ultrasound patterns appear, FNA examination or surgery is required. 5.What should I pay attention to in terms of diet for thyroid nodules? It needs to be analyzed on a case-by-case basis. First of all, we need to clarify the cause and classification of thyroid nodules, and take the appropriate diet according to the different conditions of thyroid nodules. In case of Graves’ hyperthyroidism with thyroid nodules, it is necessary to strictly avoid iodine diet, consume non-iodized salt and prohibit seafood such as kelp, seaweed and sea fish; in case of Hashimoto’s thyroiditis with nodules, it is not necessary to strictly avoid iodine, but eating a lot of food with high iodine will increase the damage of thyroid follicular cells and antibody production, which will aggravate the destruction of thyroid cells, so it is not recommended to eat a lot of seafood. If the nodule is a high-functioning adenoma that can secrete thyroid hormone, iodine should be strictly avoided because iodine is one of the raw materials for thyroid hormone synthesis, and iodine intake will also increase the synthesis of thyroid hormone and worsen the symptoms of hyperthyroidism. If it is a non-functioning nodule, which means it has no effect on thyroid function, there is no need to avoid iodine in the diet. It is recommended to consume less food such as radish and cabbage, as current studies have found that these two foods promote the growth of thyroid nodules. 6.What are the features of ultrasound that indicate thyroid cancer? Ultrasound indicates nodules with microcalcifications, local invasion, lymph node metastasis, nodules with aspect ratio greater than 1, nodules with unclear borders and irregular shape, nodules with significant hypoechogenicity, or parenchymal components with abundant blood flow in the nodules. These are the basis for suggesting that the nodule may be malignant, and the more the above-mentioned hints, the greater the possibility of malignancy, and further fine needle aspiration cytology of the thyroid nodule is needed if highly suspected.