Thyroid nodules are growths inside the thyroid gland made up of groups of abnormally reproducing thyroid cells. Although the vast majority of nodules are non-cancerous benign growths which do not cause symptoms unless by size, up to 20 percent of thyroid nodules may contain thyroid cancer. Thyroid nodules occasionally produce excessive amounts of thyroid hormone but most often thyroid nodules have no significant effect on thyroid levels. It is not well understood how or why thyroid nodules develop but when they grow, they can cause an enlarged thyroid or goiter and can result in difficulty swallowing, hoarseness, choking sensation and shortness of breath. Evaluation of thyroid nodules should include a thyroid ultrasound and checking thyroid levels and may require an FNA (fine needle aspiration) biopsy, a thyroid scan and uptake study or a CT scan. If the thyroid nodules grow large enough or if there are signs of thyroid cancer, surgery may be required to remove a portion or all of the thyroid gland.