Patient information: Thyroid nodules

OVERVIEW

The thyroid is a butterfly-shaped gland in the middle of the neck, located below the larynx (voice box) and above the clavicles (collarbones) (figure 1). Thyroid nodules are round or oval-shaped areas within the thyroid (figure 2) that can be caused by a number of conditions, most of which are not serious.

This topic discusses the tests that may be performed on thyroid nodules, as well as the treatments that are available. Other thyroid conditions are discussed separately. (See "Patient information: Hyperthyroidism" and "Patient information: Hypothyroidism" and "Patient information: Antithyroid drugs".)

WHAT DOES THE THYROID DO?

The thyroid produces two hormones, triidodothyronine (T3) and thyroxine (T4), which regulate how the body uses and stores energy. Thyroid function is controlled by a gland located just below the brain, known as the pituitary (figure 3). The pituitary produces thyroid stimulating hormone (TSH), which stimulates the thyroid to produce T3 and T4.

Thyroid nodules are very common (figure 2); up to half of all people have at least one thyroid nodule, although most do not know about it. Thyroid nodules can be caused many different conditions (table 1). Reassuringly, about 95 percent of all thyroid nodules are caused by benign (non-cancerous) conditions.

THYROID NODULE DIAGNOSIS

Diagnostic tests can determine if a thyroid nodule is benign or malignant (cancerous); this information can help to guide treatment decisions. There are several diagnostic tests and each provides unique information about the thyroid nodule. However, not every person with a thyroid nodule needs all of these tests.

Often, a test will provide a definitive answer about the type and cause of a nodule. In other cases, a test may be inconclusive and further testing will be required. Discuss which tests you will need and the results of these tests with your healthcare provider.

Thyroid stimulating hormone — Thyroid stimulating hormone can be measured with a blood test.

• If the TSH level is normal, the next step is to have a fine needle aspiration biopsy. (See 'Fine needle aspiration' below.)

• Low levels of thyroid stimulating hormone (TSH) in the blood may indicate that a nodule is producing high levels of thyroid hormone. If the TSH level is lower than normal, the next step is to have a thyroid scan (see 'Thyroid scan' below.
• High levels of TSH may indicate autoimmune inflammation of the thyroid (called Hashimoto's thyroiditis). Another blood test, to measure levels of thyroid antibodies, is often recommended in this case. (See "Pathogenesis of Hashimoto's thyroiditis (chronic autoimmune thyroiditis)".)

Fine needle aspiration — In most cases, the TSH level is normal, and the next step is the fine needle aspiration (FNA). FNA uses a thin needle to remove small tissue samples from the thyroid nodule. The tissue is examined with a microscope.

Fine-needle aspiration biopsy can be performed in the office with a local anesthetic (numbing medicine). You may feel mild discomfort as the anesthesia is injected, but you will not feel pain during the biopsy.

This test is accurate in identifying cancer in a suspicious thyroid nodule. In some cases, the biopsy does not contain enough tissue to make a diagnosis, and surgery is necessary.

The results of the biopsy will be one of the following:

• Benign (noncancerous)
• Malignant (cancer)
• Indeterminant or suspicious
• Nondiagnostic or insufficient

Thyroid scan — Most people do not have to have a thyroid scan - only those who have a low TSH level. In these cases, the thyroid scan is the first step after the blood test (instead of the fine needle aspiration).

A thyroid scan can help to determine if a thyroid nodule is autonomous ("hot") or non-functional ("cold"). The scan is performed after taking a small dose of a radioactive substance (either iodine or technetium) by pill or injection.

• Thyroid nodules that absorb the radioactive substance are usually not cancerous (called autonomous, hot, or toxic). (See 'Autonomous ('hot') thyroid nodules' below.)

• Thyroid nodules that do not absorb the radioactive substance are called cold, and have a 5 percent risk of being cancerous. Approximately 95 percent of thyroid nodules are cold.

The risk of exposure to radiation is small compared to the benefit of knowing the test results. Women who are pregnant or breastfeeding should not have a thyroid scan. Following a thyroid scan, patients should take care to flush the toilet and wash their hands after urinating because the radioactive substance is eliminated in the urine.

THYROID NODULE TREATMENT

The appropriate thyroid nodule treatment depends upon the type of thyroid nodule that is found. (See "Diagnostic approach to and treatment of thyroid nodules".)

Benign thyroid nodules — Benign thyroid nodules usually develop as a result of overgrowth of normal thyroid tissue. Surgery is not usually recommended, and the thyroid nodule can be monitored over time. If the thyroid nodule grows, a repeat biopsy or surgery may be recommended.

Suppressive (thyroid hormone) treatment — If a thyroid nodule is not cancerous, but the nodule is large, some clinicians will suggest a trial of T4 to shrink the nodule; this is called suppressive treatment. Thyroid hormone levels should be monitored carefully during suppressive treatment. (See "Thyroid hormone suppressive therapy for thyroid nodules and benign goiter".)

Indeterminate or suspicious thyroid nodules — Indeterminate thyroid nodules are not officially classified as cancerous, but they share many features with thyroid cancer. Over time, they may invade surrounding tissues, at which point they are classified as thyroid cancer.

Surgical removal of indeterminate or suspicious thyroid nodules is generally recommended. At the time of surgery, about 10 to 20 percent of suspicious thyroid nodules have become invasive and are classified as thyroid cancer.

Autonomous ('hot') thyroid nodules — Some thyroid nodules produce thyroid hormone, similar to the thyroid gland, but do not respond to the body's hormonal controls. These nodules are called autonomous thyroid nodules. They are almost always benign, but they can overproduce thyroid hormone, leading to hyperthyroidism. (See "Patient information: Hyperthyroidism".)

If you have an autonomous nodule and high levels of thyroid hormone, you will usually be advised to undergo surgery to remove the thyroid nodule, or undergo radioactive iodine treatment to destroy the nodule. (See "Treatment of toxic adenoma and toxic multinodular goiter".)

If you have an autonomous nodule and normal thyroid function or minimal hyperthyroidism, the appropriate treatment will depend on your age and other health factors.

• In young adults, autonomous nodules may be monitored over time.
• In older adults, radioactive iodine treatment may be recommended because high thyroid hormone levels pose a risk of an abnormal heart rhythm (atrial fibrillation) and bone loss (osteoporosis).

Cystic thyroid nodules — Cystic thyroid nodules are usually benign nodules that have filled with fluid. These nodules may simply collapse when the fluid is removed. Cystic nodules are usually monitored for changes. If the cyst reforms or bleeds more than once, surgery can be performed to remove the thyroid nodule. (See "Cystic thyroid nodules".)

Malignant thyroid nodules (thyroid cancer) — Only about 5 percent of all thyroid nodules are malignant. Most patients with thyroid cancer have an excellent chance for cure or long-term survival. (See "Overview of follicular thyroid cancer" and "Overview of papillary thyroid cancer".)

The treatment of thyroid cancer will depend on the type of cancer. Thyroid cancers require surgical removal of the thyroid gland and sometimes one or more treatments with radioiodine, followed by thyroid hormone (T4) suppressive therapy. (See "Overview of the management of differentiated thyroid cancer".)

SUMMARY

• The thyroid is a butterfly-shaped gland in the middle of the neck, located below the larynx (voice box) and above the clavicles (collarbones). Thyroid nodules feel round or oval-shaped, and differ from the surrounding normal thyroid tissue (figure 1)(figure 2).
• Thyroid nodules are very common; up to half of all people have at least one thyroid nodule, although most do not know about it. Thyroid nodules can be caused many different conditions (table 1). Reassuringly, about 95 percent of all thyroid nodules are caused by benign (non-cancerous) conditions.
• Diagnostic tests can determine if a nodule is benign or malignant (cancerous) and can help to guide treatment decisions. Tests include blood tests, fine needle aspiration (removing a small piece of tissue with a needle), and thyroid scan.
• The appropriate treatment for a thyroid nodule will depend upon the type of nodule. Benign nodules can usually be monitored over time. If the nodule grows, a repeat biopsy or surgery are often recommended.

WHERE TO GET MORE INFORMATION

Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two people are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.

This discussion will be updated as needed every four months on our web site (www.uptodate.com/patients). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.

Some of the most pertinent include:

Patient Level Information:
Patient information: Hyperthyroidism
Patient information: Hypothyroidism
Patient information: Antithyroid drugs

Professional Level Information:
Atlas of thyroid cytopathology
Cystic thyroid nodules
Diagnostic approach to and treatment of thyroid nodules
Overview of papillary thyroid cancer
Overview of the management of differentiated thyroid cancer
Overview of thyroid nodule formation
Thyroid hormone suppressive therapy for thyroid nodules and benign goiter
Pathogenesis of Hashimoto's thyroiditis (chronic autoimmune thyroiditis)
Treatment of toxic adenoma and toxic multinodular goiter
Overview of follicular thyroid cancer

A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable.

• National Library of Medicine

      (www.nlm.nih.gov/medlineplus/healthtopics.html)

• The American Thyroid Association

      (www.thyroid.org)

• Thyroid Foundation of Canada

      (www.thyroid.ca)

• The Hormone Foundation

      (www.hormone.org/public/thyroid.cfm, available in English and Spanish)

Patient Support — There are a number of online forums where patients can find information and support from other people with similar conditions.

• About.com Thyroid Conditions Forum

      (http://thyroid.about.com/forum)

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