Thyroid disease, commonly known as “big neck” disease, is a common and frequent disease in urban and rural areas. The prevalence rate is about 5% in the United States and even higher in China. The most common clinical condition is iodine-deficient goiter, while others include hyperthyroidism, thyroiditis, hypothyroidism, thyroid adenoma, and thyroid cancer. The causes of “big neck” disease are diverse and the treatment methods vary. The thyroid gland is located on both sides of the trachea, and its normal weight is about 20 grams. Iodine deficiency, high iodine, thyroid antibodies, tumors, endocrine disorders, malnutrition and other factors can all cause an enlarged thyroid. Therefore, once you find that your neck is enlarged, you must go to the hospital for thyroid function, immune testing, imaging and pathology examinations to clarify the cause and prescribe the right medicine.