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 tumor; 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 non-cancerous (benign) or cancerous (malignant). 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:

A hard nodule
A nodule that is stuck to nearby structures
Family history of multiple endocrine neoplasia Type II
Family history of thyroid cancer, especially medullary thyroid carcinoma
Hoarse voice due to vocal cord paralysis

Other risk factors for a cancerous nodule include:

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

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

Hashimoto's disease
Iodine deficiency
Suppression of thyroid hormone

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:

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

Thyroid nodules are found in Hashimoto's disease. Hashimoto's disease may cause hypothyroidism, with symptoms such as:

Signs and tests

Very often, nodules produce no symptoms. Doctors will find thyroid nodules only during a routine physical exam. If the doctor finds a nodule or you have symptoms of a nodule, the following tests may be done:

Treatment

Surgery is recommended for nodules that:

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

Patients with overactive nodules may be treated with radioactive iodine, which reduces the size and activity of the nodule. However, the treatment can cause hypothyroidism and inflammation of the thyroid gland (radiation-induced thyroiditis). 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 non-cancerous nodules only in special cases, including:

A growing nodule
A nodule causing pressure on other structures in the neck
Many nodules growing in the thyroid gland

Levothyroxine does not seem to benefit most people with thyroid nodules. It also can cause serious complications, including 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 need treatment have an excellent outlook.

The outlook for cancerous nodules depends on the type of cancer.

Complications

Hyperthyroidism is a common complication of non-cancerous thyroid nodules.

Complications of treatment can include:

Hoarse voice if vocal cord nerves are damaged during surgery
Hypothyroidism from surgery or radioactive iodine therapy
Low blood calcium (hypocalcemia) from hypoparathyroidism if parathyroid glands are accidentally damaged or removed during surgery

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.

If you have been exposed to radiation in the face or neck area, call your health care provider. A neck ultrasound can be done to look for thyroid nodules.

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.

Ladenson P, Kim M. Thyroid. In: Goldman L and Ausiello D, eds. Goldman: Cecil Medicine. 23rd ed. Philadelphia, Pa:Saunders; 2007:chap 244.

AACE/AME. American Association of Clinical Endocrinologists and Associazione Medici Endocrinologi. Medical Guidelines for Clinical Practice for the Diagnosis and Management of Thyroid Nodules. Endocr Pract. 2006;12:63-102.

Review Date:6/17/2008
Reviewed By:Elizabeth H. Holt, MD, PhD, Assistant Professor of Medicine, Section of Endocrinology and Metabolism, Yale University. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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