Why do people get thyroid nodules?

A thyroid nodule is a growth within the thyroid gland, which may or may not be felt by physical exam. Some nodules are only found incidentally on imaging of the thyroid. Thyroid nodules are very common and by age 60 almost one-half of all people will have a thyroid nodule. Fortunately most of these nodules are benign and do not cause any symptoms. We do not know why most thyroid nodules occur, although some conditions, such as Hashimoto’s thyroiditis (inflammation of the thyroid), a family history, radiation exposure, and iodine deficiency(rare in the United States), may increase the frequency of nodules.

For more information go to http://www.thyroid.org/what-are-thyroid-nodules/