Family history About 5% of patients with thyroid cancer have a family history of the same type of thyroid cancer. Usually, among papillary cancers, familial non-myeloid thyroid cancer is the most common, accounting for about 6.2% to 10.5% of all papillary cancer incidences. Radiation Radiation Radiation is one of the risk factors for thyroid cancer. There is also an association between childhood exposure to diagnostic radiography and the development of thyroid cancer in adulthood, and a history of previous head and neck radiation exposure and the development of thyroid cancer. Excess and deficient iodine intake Excess and deficient iodine intake may both contribute to the high incidence of thyroid cancer. Excess iodine intake may be associated with the growth of papillary thyroid cancer, and iodine deficiency may be associated with the high incidence of follicular thyroid cancer. Obesity and metabolic diseases and metabolic diseases A meta-analysis of body mass index (BMI) has shown an association between BMI and the development of thyroid cancer. Insulin resistance or hyperinsulinemia in obese individuals or patients with metabolic diseases can induce the development of thyroid cancer. Other studies on the association between dietary factors and thyroid cancer have also reported that excessive intake of smoked and preserved seafood, fats, cheeses, and starches may increase the risk of thyroid cancer, but further in-depth studies are needed.