Thyroid cancer is the most common malignant tumor of the thyroid gland, accounting for about 1% of all malignant tumors in the body. It can be divided into papillary carcinoma, follicular carcinoma, undifferentiated carcinoma, and medullary carcinoma according to the pathological type of the tumor, of which papillary carcinoma accounts for about 60% of adult thyroid cancer and all pediatric thyroid cancer. Papillary carcinoma has the best prognosis, undifferentiated carcinoma has the worst prognosis, follicular carcinoma has a worse prognosis than papillary carcinoma but better than medullary carcinoma. The etiology of thyroid cancer is not very clear, but may be related to dietary factors (high iodine or iodine deficiency diet), genetic factors, history of exposure to radiation, increased estrogen secretion, or other benign thyroid diseases such as nodular goiter, hyperthyroidism, thyroid adenoma and especially chronic lymphocytic thyroiditis. 1. Iodine and TSH: Excessive iodine intake or iodine deficiency can cause changes in the structure and function of the thyroid gland. For example, the incidence of thyroid cancer in endemic areas of Switzerland is 2ermil; 20 times higher than that of non-endemic areas such as Berlin. Conversely, a diet high in iodine also predisposes to thyroid cancer, with Iceland and Japan, the countries with the highest iodine intake, having higher rates of thyroid cancer detection than other countries. This may be related to the factor of TSH stimulating thyroid hyperplasia. Experiments have shown that long-term TSH stimulation can lead to thyroid hyperplasia, nodule formation and cancer. Genetic factors: About 5-10% of medullary thyroid carcinomas have obvious family history and are often combined with pheochromocytoma and other intercalation, so it is presumed that the occurrence of such carcinomas may be related to chromosomal genetic factors. 3.Radiation damage: irradiating the thyroid gland of laboratory rats with X-rays can promote the development of thyroid cancer in animals. It was proved that 131Ⅰ can change the metabolism of thyroid cells, deform the nucleus and greatly reduce the synthesis of thyroxine. It can be seen that on the one hand, radiation can cause abnormal division of thyroid cells, leading to cancer; on the other hand, it can destroy the thyroid gland and prevent it from producing endocrine hormone, and the resulting large secretion of thyroid stimulating hormone (TSH) can also promote thyroid cell carcinogenesis. 4.The role of sex hormones: Since there are obviously more women than men in patients with well-differentiated thyroid cancer, the relationship between sex hormones and thyroid cancer has been paid attention to. Clinical comparison of tumor sizes of well-differentiated thyroid cancer reveals that the tumors of young people are usually larger than those of adults, and the cervical lymph node metastasis or distant metastasis of thyroid cancer occurs earlier in young people than in adults, but the prognosis is better than that of adults, and there are also menstrual mothers, but It is possible that the increased secretion of estrogen is related to the occurrence of thyroid cancer in young people. Therefore, some people have studied sex hormone receptors in thyroid cancer tissues and found that there are sex hormone receptors in thyroid tissues: estrogen receptor (ER) and progesterone receptor (PR), and ER in thyroid cancer tissues. but the effect of sex hormones on thyroid cancer is still inconclusive. 5.Other thyroid lesions: There are clinical reports of thyroid adenocarcinoma, chronic thyroiditis, nodular goiter or certain toxic goiters developing cancer, but the relationship between these thyroid lesions and thyroid cancer is still difficult to be sure.