What is the major risk factor for thyroid cancer?

The major risk factor for thyroid cancer is exposure to radiation. This association is particularly noted in individuals who have received radiation therapy to the head or neck during childhood or who have been exposed to significant environmental radiation, such as following a nuclear accident.

Radiation can lead to mutations in thyroid cells, increasing the likelihood of cancerous changes. Studies have shown that those exposed to such radiation have a significantly higher risk of developing thyroid cancer later in life, especially papillary thyroid cancer, which is the most common type.

Other factors like inadequate iodine intake, the presence of a goiter, and smoking can influence thyroid health, but they are not the primary risk factors linked to thyroid cancer development in the same clear and established manner as radiation exposure. Iodine deficiency can lead to goiter formation but does not directly correlate with increased thyroid cancer risk. Similarly, while certain types of goiters can be associated with cancer, not all goiters pose an increased risk, and smoking is more associated with other types of cancers rather than being a strong risk factor for thyroid cancers specifically.