Goiter

What is goiter?

Goiter is an enlargement of the thyroid gland. The thyroid gland is a small, butterfly-shaped gland located in the neck, below your Adam’s apple.

The thyroid gland produces the hormones thyroxine (also called T4) and a small amount of triiodothyronine (also called T3). Most of the T4 is converted to T3 outside of the thyroid. These thyroid hormones influence such bodily functions as a person’s body temperature, mood and excitability, pulse rate, digestive functions, and other processes necessary for life.

What causes goiter?

Goiters have different causes depending on their type. Goiters can be classified as simple, hereditary, or due to other causes. Simple goiters are further classified as endemic (associated with iodine deficiency) or sporadic.

Simple goiters develop when the thyroid gland does not make enough thyroid hormone to meet the body’s needs. The thyroid gland tries to make up for this shortage by enlarging.

Endemic goiters occur in people within certain geographic areas who do not get enough iodine in their diet (iodine is necessary to make thyroid hormone). Lack of enough iodine in the diet is still common in parts of central Asia and central Africa. The use of iodized table salt in the United States and other countries has limited the development of this type of goiter.

Another type of simple goiter (sporadic goiters), in most cases, has no known cause. In some cases though, certain types of drugs can cause this type of goiter. Lithium (eg, used in many mental health conditions [bipolar disorder, major depression, schizoaffective disorder]) as well as other medical conditions, can cause this type of goiter. Aminoglutethimide, a drug approved to treat tumors in the adrenal glands, can also cause this type of goiter.

Hereditary factors also may cause goiters. A family history of goiter, female gender and age over 40 are all risk factors for the development of goiters.

Other diseases and conditions can also cause a goiter. These include:

• Graves’ disease. Graves’ disease is an autoimmune disease (a disease in which your body’s immune system mistakenly attacks your healthy body). In this case, the thyroid gland is attacked, causing it to over stimulate and results in the swelling of this gland.
• Hashimoto’s disease. This is another autoimmune disease. In this case, the disease causes inflammation of the thyroid gland, which in turn, results in the underproduction of thyroid hormones. Inflammation causes the gland to swell, resulting in a goiter. This type of goiter usually resolves on its own over time.
• Nodular goiter. In this condition, tissue growths (ie, nodules) occur on one or both side of the thyroid gland, resulting in an enlargement.
• Thyroid cancer. Cancer of the thyroid gland often enlarges the thyroid. Thyroid cancer can be found in thyroid nodules though less than 5 percent of nodules are cancerous. A goiter without nodules is not a concern for cancer.
• Pregnancy. A hormone secreted during pregnancy (human chorionic gonadotropin) can cause an enlargement of the thyroid gland.
• Thyroiditis. Inflammation of the thyroid gland itself can result in an enlargement of the thyroid gland. This can follow a viral illness or pregnancy.
• Exposure to radiation. A history of radiation exposure to the head and neck (from medical treatments but not from diagnostic procedures -- such as a CT scan.) increases your risk of developing goiter.

What are the symptoms of goiter?

Main symptoms include:

• A swelling, ranging in size from a small nodule to a massive lump, in the front of the neck just below your Adam’s apple
• A feeling of tightness in the throat area
• Hoarseness
• Neck vein distention.
• Dizziness when the arms are raised above the head
• Difficulty breathing (shortness of breath), coughing, wheezing (due to compression of the windpipe) are rare symptoms
• Difficulty swallowing (due to compression of the esophagus) is also rare

Other symptoms of goiters can include:

• An increased resting pulse rate
• Rapid heartbeat
• Diarrhea, nausea, vomiting
• Sweating without exercise or increased room temperature
• Shaking
• Agitation

The six symptoms listed above are also symptoms of hyperthyroidism. Hyperthyroidism is a condition in which the thyroid is overactive. Some people with goiter may also have hyperthyroidism.

Other symptoms of goiters can include:

• Fatigue, constipation, dry skin
• Weight gain
• Menstrual irregularities

The three symptoms listed above are also symptoms of hypothyroidism. Hypothyroidism is a condition in which the thyroid is underactive. Some people with goiter may also have hypothyroidism.

How is goiter diagnosed?

Several testing methods can be used to diagnose and evaluate the goiter, including:

• Physical exam – Your doctor may be able to detect enlargement of the thyroid gland by feeling the neck area for nodules and signs of tenderness.
• Hormone test – This blood test determines thyroid hormone levels, which tell if the thyroid is functioning properly.
• Antibody test – This blood test looks for certain antibodies that are produced in some forms of goiter.
• Ultrasound of the thyroid – This imaging test of the thyroid gland reveals the gland’s size and possible presence of nodules.
• Thyroid scan – This imaging test provides information on the size and function of the gland. In this test, a small amount of radioactive material is injected into a vein. This test is ordered infrequently, since it is only useful in certain circumstances.
• CT scan or MRI (magnetic resonance imaging) of the thyroid. If the goiter extends into the chest or is very large, a CT scan or MRI is used to evaluate the size and extent of the goiter.

How is goiter treated?

Treatment options depend on the size of the enlargement, symptoms, and the underlying cause. Treatments typically considered by your doctor include:

• No treatment/"watchful waiting." If the goiter is small and is not bothering you, your doctor may decide that no treatment is needed at this time. However, the goiter will be closely watched for any changes.
• Medications –  Levothyroxine (Levothroid^®, Synthroid^®) is a thyroid hormone replacement therapy. It is prescribed if the cause of the goiter is an underactive thyroid (hypothyroidism). Other medications are prescribed if the cause of the goiter is an overactive thyroid (hyperthyroidism). These drugs include methimazole (Tapazole^®) and propylthiouracil. Aspirin or a corticosteroid medication might be prescribed if the underlying cause of the goiter is inflammation. Small doses of iodine (in the form of Lugol’s or potassium iodine solution) can be prescribed if the goiter is due to iodine deficiency.
• Radioactive iodine treatment. This treatment, used in cases of an overactive thyroid gland, involves injecting radioactive iodine into the bloodstream. The iodine is delivered to the thyroid gland, killing thyroid cells, which shrinks the gland. Radioactive iodine treatment is usually followed by lifelong hormone replacement therapy.
• Biopsy. A biopsy (removal of a sample of tissue or cells) may be required if there are large nodules in the thyroid gland. A biopsy is taken to rule out cancer.
• Surgery. Surgery is performed to remove all or part of the thyroid gland. Surgery may be needed if the goiter is large and causing difficulty breathing and swallowing. Surgery is also sometimes used to remove nodules, and definitely if cancer is present. Depending on the amount of thyroid gland removed, lifelong thyroid hormone replacement therapy may be needed.

References

• American Association for Clinical Chemistry. Lab Tests Online. Thyroid Diseases. www.labtestsonline.org Accessed 1/6/2012
• Merck Sharp & Dohme Corp. The Merck Manuals Online Medical Library. Endocrine and Metabolic Disorders. Thyroid Disorders: Simple Nontoxic Goiter (Euthyroid Goiter) www.merck.com/ Accessed 1/6/2012
• American Thyroid Association. Goiter. www.thyroid.org/ Accessed 1/6/2012

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