A thyroid nodule is a lump that can develop in your thyroid gland. It can be solid or filled with fluid. You can have a single nodule or a cluster of nodules. Thyroid nodules are relatively common and rarely cancerous.

Your thyroid is a small butterfly-shaped gland located near your larynx (voice box) and in front of the trachea (windpipe). This gland produces and secretes two hormones that affect your heart rate, body temperature, and many body processes — a group of chemical reactions that collectively are known as metabolism.

Thyroid nodules are classified as cold, warm, or hot, depending on whether they produce thyroid hormones or not: Cold nodules don’t produce thyroid hormones. Warm nodules act as normal thyroid cells. Hot nodules overproduce thyroid hormones.

More than 90 percent of all thyroid nodules are benign (noncancerous). Most thyroid nodules aren’t serious and cause few symptoms. And it’s possible for you to have a thyroid nodule without even knowing it.

Unless it becomes large enough to press against your windpipe, you may never develop noticeable symptoms. Many thyroid nodules are discovered during imaging procedures (such as a CT scan or MRI scan) done to diagnose something else.

You may have a thyroid nodule and not have any noticeable symptoms. But if the nodule gets large enough, you may develop:

  • an enlarged thyroid gland, known as a goiter
  • pain at the base of your neck
  • swallowing difficulties
  • breathing difficulties
  • hoarse voice

If your thyroid nodule is producing excess thyroid hormones, you may develop symptoms of hyperthyroidism, such as:

  • rapid, irregular heartbeat
  • unexplained weight loss
  • muscle weakness
  • difficulty sleeping
  • nervousness

In some cases, thyroid nodules develop in people with Hashimoto’s disease. This is an autoimmune thyroid condition that increases the risk of developing an underactive thyroid (hypothyroidism). Symptoms of hypothyroidism include:

  • persistent fatigue
  • unexplained weight gain
  • constipation
  • sensitivity to cold
  • dry skin and hair
  • brittle nails

The majority of thyroid nodules are caused by an overgrowth of normal thyroid tissue. The cause of this overgrowth is usually unknown, but there is a strong genetic basis.

In rare cases, thyroid nodules are associated with:

  • Hashimoto’s disease, an autoimmune disease that leads to hypothyroidism
  • thyroiditis, or chronic inflammation of your thyroid
  • thyroid cancer
  • iodine deficiency

Iodine deficiency is rare in the United States due to the widespread use of iodized salt and iodine-containing multivitamins.

You’re more likely to develop thyroid nodules if:

  • you had X-rays performed on your thyroid in infancy or childhood
  • you have a preexisting thyroid condition, such as thyroiditis or Hashimoto’s disease
  • you have a family history of thyroid nodules
  • you’re 60 years of age or older

Thyroid nodules are more common in women. When they develop in men, they’re more likely to be cancerous.

You may not know you have a nodule until your doctor finds it during a general physical exam. They may be able to feel the nodule.

If they suspect you have a thyroid nodule, they will probably refer you to an endocrinologist. This type of doctor specializes in all aspects of the endocrine (hormone) system, including the thyroid.

Your endocrinologist will want to learn if you:

  • underwent radiation treatment on your head or neck as an infant or child
  • have a family history of thyroid nodules
  • have a history of other thyroid problems

They will use one or more of the following tests to diagnose and assess your nodule:

  • thyroid ultrasound, to examine the structure of the nodule
  • thyroid scan, to learn if the nodule is hot, warm, or cold (this test is typically performed when the thyroid is overactive)
  • fine needle aspiration, to collect a sample of the nodule for testing in a laboratory
  • blood tests, to check your levels of thyroid hormones and thyroid stimulating hormone (TSH)

Your treatment options will depend on the size and type of thyroid nodule you have.

If your nodule isn’t cancerous and isn’t causing problems, your endocrinologist may decide it doesn’t need treatment at all. Instead, they will closely monitor the nodule with regular office visits and ultrasounds.

Nodules that start as benign rarely turn cancerous. However, your endocrinologist will likely perform occasional biopsies to rule out the possibility.

If your nodule is hot, or overproducing thyroid hormones, your endocrinologist will probably use radioactive iodine or surgery to eliminate the nodule. If you’ve been experiencing symptoms of hyperthyroidism, this should resolve your symptoms. If too much of your thyroid is destroyed or removed in the process, you may need to take synthetic thyroid hormones on an ongoing basis.

As an alternative to radioactive iodine or surgery, your endocrinologist may try to treat a hot nodule by giving you thyroid-blocking medications.

In the past, some doctors used high doses of thyroid hormones in an attempt to shrink thyroid nodules. This practice has been largely abandoned because it was for the most part ineffective.

However, thyroid hormones may be necessary for people who have an underactive thyroid (such as those who have Hashimoto’s disease).

Your endocrinologist may also use fine needle aspiration to drain your nodule if it’s fluid filled.

There’s no way to prevent the development of a thyroid nodule. If you’re diagnosed with a thyroid nodule, your endocrinologist will take steps to remove or destroy it or simply monitor it on an ongoing basis. The majority of noncancerous nodules aren’t harmful, and many people don’t need treatment.