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 (overactive thyroid) (Beyond the Basics)" and "Patient information: Hypothyroidism (underactive thyroid) (Beyond the Basics)" and "Patient information: Antithyroid drugs (Beyond the Basics)".)
WHAT DOES THE THYROID DO?
The thyroid produces two hormones, triiodothyronine (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 by 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 (TSH) can be measured with a blood test.
●If the TSH level is normal, the next step is to have a thyroid ultrasound and fine needle aspiration biopsy. (See 'Thyroid ultrasound' below and 'Fine needle aspiration' below.)
●Low levels of thyroid 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 sometimes recommended in this case. (See "Pathogenesis of Hashimoto's thyroiditis (chronic autoimmune thyroiditis)".)
Thyroid ultrasound — A thyroid ultrasound should be performed in all patients with a suspected thyroid nodule or nodular goiter on physical examination or with nodules incidentally noted on other imaging studies (carotid ultrasound, CT, MRI, or PET scan). Thyroid ultrasonography is used to answer questions about the size and anatomy of the thyroid gland and nearby structures in the neck. Thyroid ultrasound findings can be used to select nodules that require fine needle aspiration (FNA) biopsy.
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). It can be performed by palpation or using ultrasound guidance. You may feel mild discomfort as the anesthesia is injected, and you may feel some pressure during the biopsy, but the level of discomfort is similar to a visit with the dentist.
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 a repeat biopsy is necessary. In other cases (10 percent), the result of the biopsy is indeterminate. Surgery is frequently recommended for indeterminate nodules for a definite diagnosis. In some cases, assessment of molecular markers on the needle aspirates is used to select low risk indeterminate nodules for observation rather than surgery.
The results of the biopsy will be one of the following:
●Suspicious for malignancy
●Follicular neoplasm (microfollicular nodules, including Hürthle cell lesions)
●Follicular lesion or atypia of undetermined significance (nodules with atypical cells)
●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 iodine (a pill); technetium scans may also be used (an injection), but they are less reliable.
●Thyroid nodules that absorb the radioiodine are usually not cancerous (called autonomous, hot, or toxic). (See 'Autonomous ("hot") thyroid nodules' below.)
●Thyroid nodules that do not absorb the radioiodine 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. Some surgeons recommend excision of nodules over 4 cm.
Suppressive (thyroid hormone) treatment — If a thyroid nodule is not cancerous, but the nodule is large, some clinicians will suggest a trial of thyroid hormone (T4) to shrink the nodule; this is called suppressive treatment. The American Thyroid Association guidelines do not recommend this treatment because only a small percentage of nodules shrink, and suppressive therapy may have side effects. Thyroid hormone levels should be monitored carefully during suppressive treatment. (See "Thyroid hormone suppressive therapy for thyroid nodules and benign goiter".)
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 "Differentiated thyroid cancer: Overview of management".)
Suspicious for malignancy — Nodules in this category have a 50 to 75 percent risk of malignancy. Patients with nodules that are suspicious for malignancy frequently have a total thyroidectomy because the chance that the nodule is a cancer is higher than the chance it is benign.
Follicular neoplasm — We frequently perform a thyroid scan in patients with biopsies that show follicular neoplasm. From 15 to 20 percent of follicular neoplasms prove to be cancer. Thus, if the scan shows a cold nodule, surgical removal (usually a hemithyroidectomy) is generally recommended. Molecular markers (assessed on the fine needle aspirate) are sometimes used to select low risk nodules for observation rather than surgery. Thyroid nodules that absorb the radioiodine (autonomous or “hot” nodule) are usually not cancerous, and treatment depends upon thyroid function tests and other factors (see 'Autonomous ("hot") thyroid nodules' below).
Follicular lesion or atypia of undetermined significance — Most patients who have nodules with atypical cells require repeat FNA. The optimal treatment depends upon patient factors, such as risk for thyroid cancer, and the FNA (including molecular testing), and ultrasound features of the nodule.
Nondiagnostic — A nondiagnostic biopsy does not have enough cells for interpretation. It should not be considered a negative biopsy. For patients with nondiagnostic FNA biopsies, the FNA should be repeated using ultrasound guidance.
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 (overactive thyroid) (Beyond the Basics)".)
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 or surgery 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".)
●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 and 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 by 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, thyroid ultrasound, 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 is 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.
This article will be updated as needed on our Web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.
Patient level information — UpToDate offers two types of patient education materials.
The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.
Patient information: Thyroid nodules (The Basics)
Patient information: Multinodular goiter (The Basics)
Patient information: Thyroid cancer (The Basics)
Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.
Patient information: Hyperthyroidism (overactive thyroid) (Beyond the Basics)
Patient information: Hypothyroidism (underactive thyroid) (Beyond the Basics)
Patient information: Antithyroid drugs (Beyond the Basics)
Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Atlas of thyroid cytopathology
Cystic thyroid nodules
Diagnostic approach to and treatment of thyroid nodules
Overview of papillary thyroid cancer
Differentiated thyroid cancer: Overview of management
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
The following organizations also provide reliable health information.
●National Library of Medicine
●The American Thyroid Association
●Thyroid Foundation of Canada
●Hormone Health Network
(www.hormone.org, available in English and Spanish)