A thyroid nodule is a solid or fluid-filled lump that forms within the thyroid, according to Mayo Clinic. The majority of thyroid nodules are not serious and aren't noticed until discovered by a doctor during a routine medical evaluation.
Thyroid nodules usually cause symptoms unless they get large enough to be seen or felt or when they press on the windpipe, causing shortness of breath or difficulty swallowing, Mayo Clinic states. If a thyroid nodule produces additional thyroxine, it can cause unexplained weight loss, tremor, nervousness, rapid or irregular heartbeat or heat intolerance. Thyroid nodules can be caused by iodine deficiency, overgrowth of thyroid tissue, a cyst, chronic inflammation, a goiter or thyroid cancer. Mayo Clinic recommends seeking a medical consultation for any unusual swelling in the neck or difficulty breathing or swallowing.