Thyroid cancer is more common in people who had radiotherapy treatment to the neck area at a young age. The cancer may develop years later – as many as 10 to 30 years after treatment. This risk is highest for people treated with radiotherapy when they were children. But there is a slight increased risk for anyone who has had external beam radiotherapy.
Thyroid cancer is also more common in survivors of atomic explosions or accidents. After the Chernobyl nuclear reactor accident, cases of thyroid cancer in the Ukraine rose in people exposed to radiation, particularly as children or adolescents. And thyroid cancer cases also increased in the USA after nuclear testing in Utah.
There are reports of higher rates of thyroid cancer in people exposed to radiation through their work. But these studies include information about people working before 1985 and we don’t know if people working with radiation now are increasing their risk.
People who have low levels of iodine in their body may have a higher risk of thyroid cancer after exposure to radiation than people with normal iodine levels.
In addition to iodine, selenium is needed for proper thyroid function.