What are thyroid nodules?
A thyroid nodule is an unusual growth (lump) of thyroid cells in the thyroid gland.
The thyroid is part of the endocrine system, which is made up of glands that secrete various hormones into the bloodstream. The thyroid is a butterfly-shaped organ (or gland) that is located on the front of the neck, just under Adam’s apple (larynx). The thyroid gland, which is made up of a right lobe and a left lobe, produces and releases thyroid hormones. Thyroid hormones control functions such as body temperature, digestion, and heart functions.
What causes a thyroid nodule to form?
Sometimes the thyroid begins to grow (overgrowth), causing one or more nodules to form. The reason why this happens is not known. Cancer is the biggest concern when nodules form. Fortunately, cancer is very rare – it is found in less than 5 percent of all nodules. Nodules develop more often in people who have a family history of nodules, and in people who don’t get enough iodine. Iodine is needed to make thyroid hormone.
There are different types of thyroid nodules:
- Colloid nodules. These are one or more overgrowths of normal thyroid tissue. These growths are benign (not cancer). They may grow large, but they do not spread beyond the thyroid gland.
- Thyroid cysts. These are growths that are filled with fluid or partly solid and partly filled with fluid.
- Inflammatory nodules. These nodules develop as a result of chronic (long-term) inflammation (swelling) of the thyroid gland. These growths may or may not cause pain.
- Multinodular goiter. Sometimes an enlarged thyroid (goiter) is made up of many nodules (which are usually benign).
- Hyperfunctioning thyroid nodules. These nodules produce thyroid hormone, which may lead to the development of hyperthyroidism. Hyperthyroidism can affect the heart and cause such problems as sudden cardiac arrest, high blood pressure, arrhythmias (abnormal heart rhythm), osteoporosis, and other health problems.
- Thyroid cancer. Less than 5 percent of thyroid nodules are cancerous.
How do I know if I have thyroid nodules?
Most thyroid nodules do not produce any symptoms. However, if you have several nodules or large nodules, you may be able to see them. Although rare, nodules can press against other structures in the neck and cause symptoms, including:
- Trouble with swallowing or breathing
- Hoarseness or voice change
- Pain in the neck
- Goiter (enlargement of the thyroid gland)
Hyperfunctioning thyroid nodules will sometimes cause symptoms of hyperthyroidism. Hyperthyroidism is caused by the thyroid producing too many hormones, which causes the levels of thyroid hormone in the blood to be too high. Symptoms of hyperthyroidism include:
- Muscle weakness/tremors
- Light or missed menstrual periods
- Weight loss
- Difficulty sleeping
- Enlarged thyroid gland
- Vision problems or eye irritation
- Heat sensitivity (trouble dealing with heat)
- Increase or decrease in appetite
- Shortness of breath
- Itchy skin/clammy skin
- Thinning hair
- Skin flushing (a sudden reddening of face, neck or upper chest)
- Heart palpitations (rapid or irregular heartbeat)
Thyroid nodules may also be associated with symptoms of hypothyroidism. Hypothyroidism is a condition that results from an underactive thyroid gland. This causes the levels of thyroid hormone in the blood to be too low. Symptoms of hypothyroidism include:
- Fatigue (feeling tired)
- Frequent, heavy menstrual periods
- Weight gain
- Dry, coarse skin and hair, and hair loss
- Hoarse voice
- Trouble dealing with cold temperatures
What are the risk factors for thyroid nodules?
Risk factors for developing thyroid nodules include:
- Family history. Having parents or siblings who have had thyroid nodules or thyroid or other endocrine cancers increases your chance of developing nodules.
- Age. The chance of developing nodules increases as you get older.
- Gender. Women are more likely than men to develop thyroid nodules.
- Radiation exposure. A history of radiation exposure to the head and neck (from medical treatments, but not from
diagnostic procedures, such as a CT scan) increases your risk of developing nodules.
Risk factors for developing cancerous thyroid nodules include:
- Family history of nodules
- A nodule that is hard or is stuck to a nearby structure
- Male gender
- Age younger than 20 and older than 70
- Radiation exposure
How are thyroid nodules diagnosed?
Sometimes you can feel the nodule yourself, or your doctor may discover it during an exam. However, your doctor will usually need to order one or more of the following tests:
- Thyroid hormone level test. This blood test checks the levels of hormones secreted by the thyroid gland. The hormone
levels are usually normal even if there are nodules. However, there are times when abnormal hormone levels are also
benign. Therefore, your doctor will probably order other tests.
- Thyroid ultrasound. This test uses sound waves to determine if a nodule is solid or a fluid-filled cyst. (The risk of cancer is
higher in solid nodules.) This test also checks on the growth of nodules and helps find nodules that are difficult to feel. In
addition, thyroid ultrasound is sometimes used to help guide placement of the needle during a fine needle biopsy.
- Fine-needle biopsy of the thyroid gland. With this test, the doctor uses a very thin needle to take a sample of cells from
one or more thyroid nodules. The samples are then sent to a laboratory, and most turn out to be noncancerous. However, if
the test results are “suspicious,” your doctor may repeat this test. The doctor may also suggest you have surgery to remove
the nodules in order to make an accurate diagnosis.
- Thyroid scan. In this test, a small amount of radioactive iodine is given orally. The doctor will check to see how much
of the radioactive iodine is absorbed by the nodules and how much is absorbed by normal thyroid tissue. This will help
diagnose if the nodules are malignant (cancer).
How are thyroid nodules treated?
Treatment depends on the type of thyroid nodule. Treatment options include:
- No treatment/“watchful waiting.” If the nodules are not cancerous, you and your doctor may decide that you don’t need to be treated at this time. You will see your doctor on a regular basis so he or she can watch for any changes in the nodules.
- Radioactive iodine. Your doctor may use radioactive iodine to treat hyperfunctioning thyroid nodules and goiters with several nodules. The radioactive iodine is absorbed into the thyroid gland, causing the nodules to shrink. Pregnant women and women trying to become pregnant should not have this treatment.
- Surgery. Surgery to take out the nodules is the best treatment for nodules that are cancerous, that cause symptoms (e.g., are so large that they make breathing or swallowing difficult), and that are “suspicious” (i.e., cannot be diagnosed without being taken out and examined).