Thyroid nodules form when thyroid tissue grows, although the reason for their formation is not fully understood, according to Cleveland Clinic. Cancer causes some thyroid nodules to form, but most nodules are benign and thyroid cancer is very rare. Only about 5 percent of all thyroid nodules are cancerous.
The formation of thyroid nodules is more prevalent in people with iodine deficiency, notes Cleveland Clinic. The thyroid requires iodine to make thyroid hormone that is essential for bodily functions.
There are several types of thyroid nodules, including colloid nodules, which are caused by excessive growth of normal thyroid tissue that is noncancerous and does not spread beyond the thyroid gland, although these nodules can grow to become quite big. Thyroid cysts are another type of nodule; these are partially solid or fluid-filled. Inflammatory thyroid nodules occur due to chronic thyroid gland inflammation. Multinodular goiters are those that are made up of many nodules, although they are usually benign. Hyperfunctioning thyroid nodules cause an overproduction of thyroid hormone that can lead to hyperthyroidism and other complications, according to Cleveland Clinic.
Treatment for thyroid nodules generally involves watchful waiting to monitor any changes in the nodules. Thyroid hormone suppression therapy may also be used to halt the growth of nodules. Radioactive iodine treatment is sometimes used to destroy the nodules, while surgery to remove them is sometimes the best course of treatment, according to Cleveland Clinic.