Recently, thyroid nodules have been added to many medical checkups, and after the checkups, many thyroid nodules have been found, which has caused some worries among people. In fact, thyroid nodules are very common, so let us introduce to you the current situation. First of all, let’s understand what thyroid nodules are. In medical terms, thyroid nodules are defined as discontinuous damage in the thyroid gland, which is clearly distinguishable from the surrounding thyroid parenchyma in imaging. In other words, a thyroid nodule is considered a nodule only if it is detected by ultrasound or CT; a nodule that is not confirmed on ultrasound, although it can be palpated, cannot be diagnosed as a thyroid nodule. Nodules that are not palpable on physical examination but are found incidentally on imaging are called “accidental thyroid nodules”. After we understand the concept of thyroid nodules, let’s go over why the incidence of thyroid disease is so high. Thyroid nodules are a very common condition. The detection rate by palpation in the general population is 3-7%, while the detection rate by high-resolution ultrasound is 20%-76%, which may be closely related to the development of detection technology nowadays. In the past, when the thyroid gland was examined by physical examination, it was mostly done by surgical palpation. The location of the thyroid gland is hidden, and it is often difficult to detect small thyroid nodules, and the detection rate of nodules is also very low because of the experience of the detectors; nodules can also appear if you eat too much iodine. Being located on the coast, people eat a lot of seafood with high iodine content for a long time, which itself is not iodine deficient, plus the iodized salt that is usually added to the diet, which may cause iodine overdose. According to the analysis, this may be related to the excessive amount of iodine people consume. What kind of nodules need to be evaluated? Most thyroid nodules have no clinical symptoms. When combined with abnormal thyroid function, corresponding clinical manifestations may occur. Some patients have symptoms of pressure such as hoarseness, breathlessness, and breathing/swallowing due to nodule compression of surrounding tissues. 5-15% of thyroid nodules are malignant, both thyroid cancer. The clinical management of benign and malignant thyroid nodules varies greatly, as does the impact on the patient’s quality of life and the medical costs involved, so the key point in the evaluation of thyroid nodules is the differentiation between benign and malignant. This is what causes people to talk about “nodules”. Only nodules larger than 1 cm should be evaluated because they are more likely to be malignant; a few nodules smaller than 1 cm also need to be evaluated, such as nodules with suspicious malignancy on ultrasound, lymph node lesions, nodules with rapid growth, history of head and neck radiation, family history of thyroid cancer, and males; a few nodules smaller than 1 cm that do not have the above characteristics may be malignant, but the costs and benefits outweigh the benefits. However, in terms of cost-benefit ratio, the disadvantages outweigh the benefits, which means that even if the nodules are malignant, there is no need to treat them. So how do our doctors evaluate them? The American Thyroid Association considers the most common and important tests to be serum TSH (thyrotropin) and thyroid ultrasound, thyroid imaging and thyroid aspiration if necessary. A thyroid nodule with a lower than normal TSH needs to be ruled out as a high-functioning adenoma, which is rarely malignant, so cytology is not necessary. Thyroid nodules with elevated TSH levels, even at the upper limit of normal levels, have an increased risk of nodule malignancy. High-resolution ultrasound is the preferred method of evaluating thyroid nodules, and neck ultrasound should be performed for any suspicion on palpation or if a “thyroid nodule” is indicated on X-ray, CT, MRI, or PET-CT. Neck ultrasound can confirm the presence of a “thyroid nodule”, determine the size, number, location, morphology and other important information about the nodule, and assess the status of the lymph nodes in the neck area. CT, MRI, and PET-CT are not recommended as routine tests for the evaluation of thyroid nodules, but the sensitivity (83%) and specificity (92%) of the diagnosis of thyroid cancer can be greatly improved with fine needle aspiration pathology, which can help reduce unnecessary thyroid nodule surgery and help determine the appropriate surgical plan. For thyroid nodules that are still not diagnosed as benign or malignant by thyroid fine needle aspiration, molecular marker testing for thyroid cancer can be performed on the aspiration specimen. Most benign nodules can be followed up every 6-12 months, and if the size is stable, the follow-up interval can be extended to 3-5 years. If a nodule is found to be significantly enlarged during the follow-up, especially if it has signs of malignancy, it should be seen by a thyroid specialist in a timely manner.