A thyroid nodule is a mass or masses of abnormal tissue structure in the thyroid gland due to various causes. Thyroid nodules are the most prevalent and most difficult type of endocrine disorder to manage, and to date, there is no specific method to distinguish benign from malignant nodules. Thyroid nodules are very common. The prevalence of thyroid nodules in the general population is 3% to 7% on palpation, while the prevalence of thyroid nodules on high-resolution ultrasonography is 20% to 70%. Most thyroid nodules are positive, and malignant nodules account for only about 5% of thyroid nodules. Etiology and classification 1. Proliferative nodular goiter: high or low iodine, consumption of goiter-causing substances, goiter-causing drugs or defective thyroid hormone synthesis enzymes; 2. Neoplastic nodules: benign thyroid adenoma, thyroid carcinoma; 3. Cysts: nodular goiter, degenerative adenoma and old bleeding with cystic changes; 4. Inflammatory nodules: subacute thyroiditis, chronic lymphocytic thyroiditis can be seen in the form of nodules.