A thyroid nodule is an unusual lump (growth) of cells on your thyroid gland. Your thyroid gland is a small, butterfly-shaped endocrine gland located in your neck, below your Adam's apple. It produces the hormones thyroxine (also called T4) and triiodothyronine (also called T3). These hormones play a role in certain bodily functions, including: Metabolism. Body temperature. Mood and excitability. Pulse and heart rate. Digestion. Thyroid nodules are classified as: Solitary (a single nodule). Multiple (more than one nodule). Cystic (fluid-filled). Solid. More than 90% of detected nodules in adults are noncancerous (benign), but they may represent thyroid cancer in approximately 4.0% to 6.5% of cases. Even though most thyroid nodules aren’t cancer, they can sometimes be a sign of and/or cause of thyroid disease. Anyone can have a thyroid nodule, including children and adults. However, they’re about four times more common in females than males. Healthcare providers detect them in approximately 5% to 7% of adults during a physical examination. Ultrasound imaging reveals that 20% to 76% of adults have thyroid nodules. Most thyroid nodules don’t cause symptoms. However, if you have several nodules or large nodules, you may be able to see them. In rare cases, nodules can grow big enough to cause symptoms like: Trouble with swallowing or breathing. Hoarseness or voice changes. Pain in the front of your neck. Enlargement of your thyroid gland (goiter)