Thyroid nodules are abnormal overgrowths of tissue in the thyroid gland that are most often benign—but may be cancerous in some people. Some people have one nodule while others have many. Thyroid nodules may be solid tissue or filled with blood or other fluid. Thyroid nodules are quite common, with as many as half of all people having at least one nodule by the age of 60.
Do thyroid nodules cause symptoms?
Thyroid nodules most often do not cause symptoms. However, sometimes the tissue in a nodule makes too much of the thyroid hormones triiodothyronine (T3) and thyroxine (T4), and you may have the following symptoms of hyperthyroidism, which means your thyroid is overactive:
In addition, larger nodules may cause difficulty swallowing or breathing, hoarseness, and neck pain.
What may cause thyroid nodules?
The cause of one or more thyroid nodules is often unknown. Nodules run in families, meaning that they may have a genetic basis. In addition, nodules are found in people with iodine deficiency, which is not common in the United States. Rarely, cancer is the cause of this overgrowth of tissue, which is why it is important to see a doctor if you think you have a nodule.
Furthermore, the risk for thyroid nodules is higher in women than men, incidence increases with age, and is greater in people exposed to radiation from medical treatments or who have Hashimoto's disease, which is the most common cause of hypothyroidism (underactive thyroid).
How are thyroid nodules diagnosed?
Your doctor can detect a thyroid nodule by examining your neck to feel your thyroid gland. If you have a thyroid nodule, your doctor may use ultrasound to see what the nodule looks like and may take a small sample of the nodule cells to rule out cancer.
When a sampling a nodules' cells for testing, the procedure is called a biopsy or fine-needle aspiration (FNA). The cells are microscopically examined by a pathologist. The biopsy involves using a very small needle to capture the cells. The procedure is generally uncomfortable, but not painful. To help reduce your discomfort, your doctor may numb the skin area with a topical anesthetic, which is a cream that contains short-acting pain medication.
Also, your doctor may take a blood sample to measure levels of T3 and T4—the thyroid hormones, and thyroid-stimulating hormone (TSH). TSH is a hormone made by the pituitary gland to regulate the thyroid's production of T3 and T4. These blood tests cannot detect if a thyroid nodule is cancerous, but will help rule out other thyroid conditions.
How are thyroid nodules treated?
Most thyroid nodules are not cancer, and your doctor will simply monitor you with ultrasound and a physical examination at least once a year. If the nodule continues to grow and/or causes breathing/swallowing problems or develops cancerous features over time, your doctor may recommend surgical removal. If the nodule has cancer cells, an endocrine surgeon will remove it.
Nodules that make too much of the thyroid hormones T3 and T4 may be treated with radioactive iodine or alcohol ablation. Radioactive iodine is given as a pill and causes the thyroid gland to shrink and make less thyroid hormone. Radioactive iodine is only absorbed by the thyroid gland, so it does not harm other cells within your body. Alcohol ablation involves injecting alcohol into the thyroid nodule(s) using a very small needle. The treatment causes the nodules to shrink and make less thyroid hormone.
American Thyroid Association. Thyroid Nodules. June 2012. http://www.thyroid.org/what-are-thyroid-nodules/. Accessed January 12, 2015.
National Endocrine and Metabolic Diseases Information Service (NEMDIS). Thyroid Tests. February 2014. http://www.endocrine.niddk.nih.gov/pubs/thyroidtests/index.aspx#nod. Accessed January 12, 2015.
Office of Women's Health, U.S. Department of Health and Human Services. Thyroid Disease Fact Sheet. July 2012. http://womenshealth.gov/publications/our-publications/fact-sheet/thyroid-disease.html#g. Accessed January 12, 2015.