What is a thyroid nodule? Thyroid nodules are the most common type of thyroid condition, with the incidence increasing year by year. Epidemiological surveys show that the prevalence of palpable thyroid nodules in adults is 4-8%, and the detection rate of thyroid nodules in the United States is reported to be as high as 19-67%, with women and the elderly population being more common. Thyroid nodules are divided into two categories: benign and malignant. Benign lesions account for about 95% and malignant lesions account for only about 5% (91% of which are differentiated thyroid cancer, 5% are medullary thyroid cancer and only 3% are undifferentiated thyroid cancer). Possible factors for malignancy of thyroid nodules The current consensus academic opinion suggests that malignant thyroid nodules are: 1. having a palpable thyroid nodule at the age of >70 years; 2. having received a history of head, neck or whole body radiation (radiation therapy for tumor or bone marrow transplantation); 3. having a first-degree relative with thyroid cancer; 4. having a rapidly growing nodule; 5. having hoarseness; 6. having vocal cord paralysis; and 7. Enlarged and fixed lymph nodes in the neck ipsilateral to the nodule. Treatment of malignant thyroid nodules The current consensus is to perform total or near-total thyroidectomy, followed by radioiodine removal of residual thyroid tissue and thyroid hormone suppression therapy. If the nodule increases in size (15% increase in volume or 20% increase in diameter), repeat FNAC, especially ultrasound-guided FNAC, and decide the treatment according to the results. The effect of thyroxine on benign thyroid nodules: in areas of low iodine intake, benign nodules may shrink when levothyroxine (L-T4) is administered and TSH is suppressed; in areas of adequate iodine supply, no such effect is seen. Consensus opinion does not recommend routine use of thyroxine suppression therapy for benign thyroid nodules. Management of thyroid nodules in children Thyroid nodules in children are less common than in adults, have a malignancy rate equal to or higher than that of adults, and are evaluated and treated in the same way as adults (clinical evaluation, laboratory evaluation, evaluation of ancillary tests, etc.). Management of thyroid nodules in pregnancy The evaluation of thyroid nodules in pregnancy is the same as in non-pregnant women, except that thyroid nuclei imaging cannot be performed. In pregnant women with normal or hypothyroidism with thyroid nodules, FNAC should be performed; if TSH levels are still suppressed after the third trimester, ultrasonography and FNAC should be performed after delivery; if malignant nodules are found in early pregnancy, ultrasound monitoring and nodule growth may be an option for surgery at 24 weeks of pregnancy; if nodules are stable in size by mid-pregnancy, or if malignant nodules are found in late pregnancy, surgery after delivery may be an option.