Thyroid nodules can be caused by a variety of etiologies. 1.Proliferative nodular goiter High or low iodine intake, consumption of goiter-causing substances, consumption of goiter-causing drugs or defective thyroid hormone synthetase, etc. 2.Neoplastic nodules Benign thyroid tumors, papillary thyroid tumors, follicular cell carcinoma, medullary thyroid carcinoma, undifferentiated carcinoma, lymphoma and other follicular cell and non-follicular cell malignant tumors of the thyroid gland, and metastatic carcinoma. 3.Cysts Nodular goiter, degenerative adenoma and old hemorrhagic spot cysts, cystic thyroid cancer, congenital thyroglossal cysts and cysts caused by the remnants of the fourth gill slit. 4. Inflammatory nodules Acute suppurative thyroiditis, subacute suppurative thyroiditis, and chronic lymphocytic thyroiditis can all appear in the form of nodules. In rare cases, thyroid nodules are due to tuberculosis or syphilis.