In the United States, toxic nodular goiter is responsible for 15 to 30% of cases of hyperthyroidism, second only to Graves' disease. In areas of the world where iodine deficiency is endemic, goiter is the most common cause of hyperthyroidism. Frequency increases with age, especially after age 50 years, and the condition is more common in women than men.
Pathogenesis
Toxic nodular goiter runs the spectrum from a single hyper-functioning nodule (called a toxic adenoma) to multiple nodules (toxic multinodular goiter). The nodules usually result from rapid division of thyroid cells that have some growth advantage. These nodules are generally benign.
Presentation
Individuals affected with nodular goiter may have few or no symptoms, or may have many of the classic symptoms of hyperthyroidism, which include:
- Palpitations, fast heart rate
- Nervousness, trembling hands
- Weight loss
- Moist skin, heat intolerance
- Increased bowel movements
Diagnosis
Diagnosis begins with discussion of symptoms with a physician. The thyroid gland is closely examined; the physician will often palpate the neck (below the chin) to determine whether the gland is enlarged in size or has nodular "bumps." A series of lab tests are then ordered, beginning with thyroid stimulating hormone (TSH). Based on whether the TSH levels are high, normal, or low, the physician will then order additional testing. If indicated the physician may refer the individual to an endocrinologist, a physician who specializes in diseases of the thyroid gland.
Management
After a diagnosis is made, treatment is initially aimed at alleviating symptoms. This is often accomplished with a group of medications known as beta blockers. This class of medication often provides significant symptom control. Another class of medications (called thionamides) is often reserved for use in the elderly, in patients with severe symptoms, or in patients in whom immediate definitive treatment (surgery or destruction of the gland with radioactive iodine) is considered risky.
Definitive treatment for toxic nodular goiter often involves radioactive iodine ablation. This procedure takes advantage of the fact that the thyroid gland takes up iodine from the blood to build many of the important thyroid hormones. In this procedure, a solution or capsule containing radioactive iodine is administered, and the iodine rapidly concentrates in the thyroid gland. The procedure is highly effective and painless, with cure rates up to 85% after a single dose. The most common complication is hypothyroidism (inadequate functioning of the thyroid gland), which may happen years after the procedure. For this reason, patients who undergo ablation should continue to follow up with their physician for periodic blood tests.
In the elderly or individuals with other serious health problems, the physician may decide to treat symptoms first (with thionamide medications) for several weeks before proceeding with ablation. Radioactive iodine ablation should be performed under the supervision of an experienced endocrinologist. Since radioactive material is given, the procedure is not done in pregnant women. While the notion of ingesting a radioactive material may sound frightening, there has been no documented increase in risk of other cancers (such as thyroid cancer or leukemia) or infertility after treatment with radioactive iodine.
The other major treatment option for toxic goiter involves surgery. Surgical removal of all or part of the thyroid gland is often reserved for:
- Very large goiters
- Pregnant women and those younger than 40 years
- Those who decline radioactive iodine ablation
The cure rates after surgery are comparable to those seen after radioactive iodine ablation. Both options carry their own risks and deciding which treatment to undergo is an individualized decision made in close consultation with a physician.
References:
Davis AB. Goiter, toxic nodular. Emedicine Web site. http://www.emedicine.com/MED/ topic920.htm. Updated September 12, 2008. Accessed October 26, 2008.
Reid JR, Wheeler SF. Hyperthyroidism: diagnosis and treatment. Am Fam Physician. 2005;72(4):623-630.
Sarkar SD. Benign thyroid disease: what is the role of nuclear medicine? Semin Nucl Med. 2006;36(3):185-193.
