Health Encyclopedia

Thyroid nodule

Definition

A thyroid nodule is a growth (lump) in the thyroid gland. The thyroid gland is located at the base of the neck.

Alternative Names

Thyroid adenoma; Thyroid carcinoma; Thyroid incidentaloma

Causes, incidence, and risk factors

Thyroid nodules are growths of cells in the thyroid glands. These growths can be benign (non-cancerous) or malignant (cancerous). Some nodules are fluid-filled (cysts), while others are completely made of thyroid gland cells. Sometimes, what feels like one nodule will actually be a collection of small nodules close together.

Thyroid nodules that are big enough to feel during a physical exam occur in 5 - 7% of the population. Smaller nodules occur in as many as 50% of people aged 60 or older. Thyroid nodules are more common in women than in men. A person's chance of a thyroid nodule increases with age.

Only 4 - 5% of thyroid nodules are cancerous. (See: Thyroid cancer)

The following characteristics increase the risk for a cancerous nodule:

Family history of medullary thyroid carcinoma
Family history of multiple endocrine neoplasia Type II
A hard nodule
A nodule that is stuck to nearby structures
Vocal cord paralysis

Other risk factors for a cancerous nodule include:

Male gender
Age -- younger than 20 years or older than 70
History of radiation exposure to the head or neck

Causes of thyroid nodules are not always found, but can include:

Iodine deficiency
Suppression of thyroid hormone
Hashimoto's disease

Symptoms

Most thyroid nodules produce no symptoms.

Large nodules can press against other structures in the neck. Symptoms may include:

Nodules that produce thyroid hormones will cause symptoms of hyperthyroidism, including:

Weight loss
Increased appetite
Nervousness
Restlessness
Clammy skin
Skin blushing or flushing
Bounding pulse

Thyroid nodules resulting from Hashimoto's disease may cause symptoms of hypothyroidism, including:

Signs and tests

Very often, doctors will find thyroid nodules only during a routine physical exam, because the nodules produce no symptoms. When a doctor finds a nodule, or when there are symptoms that suggest a nodule, your doctor may order the following tests:

TSH level
Fine needle aspiration biopsy
Thyroid ultrasound
Thyroid scan -- a nodule that works apart from the thyroid gland is said to be "warm" or "hot," and will appear darker on the scan. Only 1% of working nodules are cancerous. Approximately 20% of cold (non-working) nodules are cancerous.
T3 and T4 levels

Treatment

Some thyroid nodules disappear without treatment. Surgery is recommended for nodules that:

Are cancerous
Cause symptoms
Cannot be diagnosed as cancer or non-cancer

Patients with working nodules sometimes receive treatment with radioactive iodine, which reduces the size of the nodule. However, the treatment can cause hypothyroidism and radiation-induced thyroiditis (inflammation of the thyroid gland). Pregnant women should not be given this treatment. Women being treated with radioactive iodine should not get pregnant.

Levothyroxine (Synthroid, Levoxyl, Levothroid, Unithroid) is a drug that suppress the production of the thyroid hormone T4. A doctor may prescribe levothyroxine to treat benign nodules only in special cases, including:

A growing nodule
A nodule causing pressure on other structures in the neck
When many nodules are growing in the thyroid gland

Levothyroxine does not seem to benefit most people with thyroid nodules, and can cause serious complications. Complications include heart problems and loss of bone density.

Careful follow-up is the only recommended treatment for benign nodules that do not cause symptoms and are not growing. A thyroid biopsy may need to be repeated 6-12 months after diagnosis. An ultrasound may be repeated as well.

Newer treatments include ethanol (alcohol) injection into the nodule and laser therapy.

Expectations (prognosis)

Non-cancerous thyroid nodules are not life threatening. Many do not require treatment, only follow-up. Non-cancerous nodules that do require treatment have an excellent outlook.

The outlook for cancerous nodules depends on the type of cancer. See Thyroid cancer for more information.

Complications

Hyperthyroidism is a common complication of non-cancerous thyroid nodules. Complications of treatment can include:

Nodule regrowth
Scarring from surgery
Hoarseness or voice changes as a result of vocal cord damage during surgery -- this happens especially if the nodule is close to the voice box
Heart-related problems as a result of side effects from medication
Weak bones resulting from medication treatment
Hypothyroidism

Calling your health care provider

Call your health care provider if you feel or see a lump in your neck, or if you experience any symptoms of a thyroid nodule.

Prevention

The reason for most thyroid nodules is unknown. A diet with enough iodine will help prevent some nodules.

References

Sriram U, Patacsil LM. Thyroid Nodule. Dis Mon 2004; 50(9):486-526.

Hegedus L. The Thyroid Nodule. N Eng J Med 2004;351:1764-71.

Goldman L, Ausiello D. Cecil Textbook of Medicine, 22nd ed. Philadelphia, Pa: WB Saunders; 2004.

Rakel RE. Textbook of Family Practice. 6th ed. Philadelphia, Pa: WB Saunders; 2005.

Review Date:5/11/2006
Reviewed By:Rita Nanda, MD, Department of Medicine, Section of Hematology/Oncology, University of Chicago Medical Center, Chicago, IL. Review provided by VeriMed Healthcare Network.

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