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 the 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:

  • Irritability/nervousness
  • 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 (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
  • Forgetfulness
  • Weight gain
  • Dry, coarse skin and hair, and hair loss
  • Hoarse voice
  • Trouble dealing with cold temperatures
  • Weakness/irritability

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