According to U.S. statistics, the incidence of thyroid cancer increased 2.4 times over the 30-year period from 1973-2003, making it the fastest-rising solid tumor, and its mortality rate ranked second among cancers. Among them, women are three times more likely to develop thyroid cancer than men. In Tianjin, China, the incidence of thyroid cancer increased by 193% in the 20 years from 1981 to 2001, with a dramatic increase in the incidence in women over 60 years of age. The exact cause of thyroid cancer is still inconclusive, but the recognized influencing factors are radiation, deterioration of benign thyroid nodules, genetics and diet. Iodine intake is the raw material for synthesizing thyroid hormones, and iodine intake has a close relationship with the development of thyroid disease. Investigation shows that iodine intake has a “U” relationship with the incidence of thyroid disease, that is, low or high iodine intake will lead to thyroid disease. About 7% of medullary thyroid cancers have obvious family history and are often combined with pheochromocytoma, so it is presumed that the occurrence of such cancers may be related to chromosomal genetic factors. 3.Radiation damage Research shows that exposure to radioactive substances in the head and neck is an important factor in thyroid cancer, such as electrical appliances and CT, which we are exposed to in our daily life, will increase the chance of occurrence of thyroid cancer. In addition, the incidence of thyroid cancer is significantly higher in women with occupational exposure to ionizing radiation such as X-rays and CT. 4. Other thyroid lesions Clinically, there are reports of thyroid cancer, chronic thyroiditis, nodular goiter, etc., but the relationship between these thyroid lesions and thyroid cancer is not yet certain. The incidence rate of thyroid cancer in women is obviously higher than that in men, and the ratio of male to female is 1:3. The higher incidence rate in women may be related to the level of female estrogen. In addition, the increase of thyroid cancer incidence may be related to the popularization of color ultrasound technology, the improvement of ultrasonographers’ examination level and the improvement of the accuracy and sensitivity of the instruments.