Thyroid cancer can bring great harm to patients. Nowadays, many people ignore the timely treatment of this disease because they don’t understand the causes of thyroid cancer, and as a result, they suffer from this disease. Genetic factors: About 5-10% of medullary thyroid cancers have obvious family history and are often combined with pheochromocytoma, so it is presumed that the occurrence of these cancers may be related to chromosomal genetic factors. 2.Iodine and TSH: Excessive iodine intake or iodine deficiency can change the structure and function of thyroid gland. For example, the incidence of thyroid cancer in endemic areas of Switzerland is 2ermil, which is 20 times higher than that in non-endemic areas such as Berlin. Conversely, a diet high in iodine also predisposes to thyroid cancer, and Iceland and Japan, the countries with the highest iodine intake, have 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 contribute to thyroid hyperplasia, nodule formation and cancerous changes. 3. Other thyroid lesions: There are clinical reports of thyroid adenocarcinoma, chronic thyroiditis, nodular goiter or some toxic goiters becoming cancerous, but the relationship between these thyroid lesions and thyroid cancer is not yet certain. For example, most of the thyroid adenomas are follicular type and only 2-5% are papilloma; if thyroid cancer is transformed from adenoma, most of them should be follicular type, but in fact, more than half of the thyroid cancers are cephalic carcinoma, so it is presumed that the incidence of thyroid adenoma carcinoma is also very small. 4.Radiation damage: irradiating the thyroid gland of laboratory rats with X-rays can promote the development of thyroid cancer in animals. It is proved that 131Ⅰ can cause changes in the metabolism of thyroid cells, the nucleus is deformed and the synthesis of thyroxine is greatly reduced. It can be seen that on one hand, radiation causes abnormal division of thyroid cells and leads to cancer; on the other hand, the thyroid gland is destroyed and cannot produce endocrine hormone, and the resulting secretion of thyroid stimulating hormone (TSH) can also promote thyroid cell carcinogenesis. 5.Familial factors and thyroid cancer: Thyroid cancer is less common as an independent familial syndrome, but can be part of a familial syndrome or hereditary disease. A few families have a tendency to develop multifocal well-differentiated thyroid cancer, thyroid cancer and familial colonic polyposis (such as Gardner syndrome), including adenomatous polyps of the colon combined with soft tissue, most often with fibromatosis, combined with fibrosarcoma , is an autosomal dominant disorder caused by mutations in the APC gene located on chromosome 5q21 to q22, the latter being a signaling protein involved in the regulation of cell proliferation, and in a small number of individuals can develop carcinoma, thyroid cancer, under TSH stimulation. In clinical practice, many facts indicate that thyroidogenesis is associated with the action of radiation. Of particular interest is the fact that children who have been treated with radiation to the upper mediastinum or neck during infancy for thyroid enlargement or lymphadenopathy are particularly susceptible to thyroid cancer, because the cells of children and adolescents proliferate vigorously and radiation is an additional stimulus that predisposes them to tumor formation. In adults, thyroid cancer is less likely to occur after neck radiation therapy.