You are female. Women are more likely than men to develop thyroid nodules.
You have been exposed to radiation. Exposure to environmental radiation or past radiation treatment to your head, neck, and chest (especially during childhood) increases your risk for thyroid nodules.
You do not get enough iodine. Iodine deficiency is rare in the United States, but it is common in areas where iodine is not added to salt, food, and water. An iodine deficiency may result in an enlarged thyroid gland (goiter), with or without nodules.