The thyroid gland is an important endocrine organ of the body, located in the middle of the neck and lying in a “butterfly shape” in front of the trachea, which secretes thyroxine, an important substance for the normal functioning of the body. The increasing incidence of thyroid cancer is related to a number of factors, the most important of which is the early detection of cancer by ultrasound. In addition, thyroid cancer is also associated with electromagnetic radiation, dietary iodine overdose or iodine deficiency, benign thyroid lesions, female estrogen levels, obesity, and family genetics. Among them, the only clear cause is electromagnetic radiation, while others are only related factors. 1.Improvement of medical examination technology: With the continuous improvement of living standard, people’s health awareness is gradually enhanced and the number of regular medical checkups is increasing, especially in recent years, ultrasound examination of thyroid gland has been added to the medical checkup items, so that early thyroid cancer which was not detected in the past, especially the tiny cancer less than 1 cm in diameter, can be detected now, which has largely improved the detection rate of thyroid cancer. Therefore, it can be said that the improvement of medical examination technology is the main reason for the increase of thyroid cancer incidence directly. 2.Electromagnetic radiation: The occurrence of thyroid cancer is related to the radioactive damage to thyroid gland by electromagnetic radiation, such as high-energy γ and χ. The most typical case is the incidence of thyroid cancer among children in the former Soviet Union after the nuclear leak at Chernobyl nuclear power plant in 1986. Clinical investigations have also shown that some patients have a history of having neck x-ray treatment or multiple x-ray examinations during childhood. As for ordinary electromagnetic radiation, such as cell phone signal, wireless Wi-Fi, microwave oven, etc., so far, there is no evidence to prove that it is related to thyroid cancer. 3. Excess or lack of iodine: There are rumors among the people that consumption of iodized salt or seafood containing iodine will cause thyroid cancer. In fact, epidemiological surveys at home and abroad have shown that there is no clear relationship between the consumption of iodized salt and the occurrence of thyroid cancer. At present, it is believed that the main reason for the significantly higher incidence of thyroid cancer in coastal areas compared with inland areas is the advanced living standard and medical technology in coastal areas, and more people have thyroid cancer detected at an early stage, not due to the consumption of seafood. On the contrary, the incidence of thyroid cancer is significantly higher in iodine-deficient areas and areas with a large amount of iodine in well water. 4. Thyroid diseases: Some thyroid lesions, such as thyroid adenoma, chronic thyroiditis, nodular goiter, or other toxic goiters have an increased possibility of combining with thyroid cancer in patients. It should be emphasized that these thyroid lesions are not precancerous, but the factors that cause these benign lesions to occur overlap with those of thyroid cancer, such as low iodine and female hormones, resulting in benign thyroid disease and thyroid cancer occurring “together”. 5. Female hormones: Thyroid cancer prefers women, especially young and middle-aged women, and the incidence rate is about 1:3.5, indicating that female hormones are related to thyroid cancer. Family history: The occurrence of thyroid cancer is also related to family. 10%-15% of patients’ immediate family members may have thyroid cancer, and the risk of thyroid cancer in people with family history of thyroid cancer is 5-6 times higher than that of the general population. 7. Obesity: Epidemiological confirmation shows that overweight and obesity increase the risk of cancer. High body mass index (also known as BMI, weight divided by height squared) is a factor related to the occurrence of thyroid cancer, and obesity may only be a phenomenon, inherently it may be related to hormonal and endocrine disorders. As with all carcinogenesis, thyroid carcinogenesis may be the result of a combination of factors, including multiple oncogene mutations, and oncogenes have been identified including BRAF, RET, and RAS. It should be emphasized that although the incidence of thyroid cancer is increasing rapidly, the treatment effect is very good. Among thyroid cancers, most of them are papillary cancers with the best curative effect, and the survival rate of 20 years is over 90%. Therefore, patients do not need to worry too much, as long as they go to regular hospitals, most patients’ life expectancy and quality of life will not be greatly affected.