Goiter is noncancerous enlargement of the thyroid gland.
In most of the world, the most common cause of goiter is a diet that does not contain enough iodine. The thyroid gland uses iodine to make thyroid hormone. When there is not enough iodine, the thyroid gland grows larger in an attempt to compensate. However, in the United States, most salt is fortified with iodine, so lack of iodine is not a common cause of goiter. Other causes of goiter include use of certain drugs (for example, amiodarone or lithium) and eating certain foods in unusually large amounts. Foods that can cause goiter include cassava, broccoli, cauliflower, and cabbage. Sometimes a goiter forms temporarily during puberty, pregnancy, or menopause. In people with goiter, the thyroid gland produces normal amounts of thyroid hormones, so people do not have hypothyroidism (see Hypothyroidism) or hyperthyroidism (see Hyperthyroidism).
The thyroid gland also can enlarge if it becomes inflamed (thyroiditis, such as Hashimoto's thyroiditis, see Hashimoto's Thyroiditis) or if thyroid cancer develops. Thyroid enlargement from inflammation or cancer is not considered a goiter.
People typically notice a swelling at the base of the neck but have no other symptoms. Sometimes the goiter presses on nearby tissue and causes cough, hoarseness, or difficulty breathing or swallowing. In people with thyroiditis, the gland usually is painful and tender to the touch.
Doctors usually do blood tests to determine how the gland is functioning (thyroid function tests). They measure blood levels of the thyroid hormones thyroxine (T4) and triiodothyronine (T3) and thyroid-stimulating hormone (TSH). Sometimes doctors also look for abnormal thyroid anitbodies in the blood, which are a sign of thyroid inflammation.
Doctors do a radioactive iodine uptake test and a thyroid scan. For these tests, the person ingests (or is injected with) a small amount of radioactive iodine. The radioactive iodine concentrates in the thyroid gland. A scanner can detect how much iodine is taken up by the gland and a gamma camera (which detects radiation) produces a picture of the thyroid gland. These scans show any physical abnormalities in the gland that might suggest Graves' disease, nodules, or thyroiditis.
Treatment depends on the size and cause of goiter.
In iodine-deficient areas, people are given iodine supplements. Iodine may be added to salt, water, crops, or animal fodder to eliminate iodine deficiency in the area. People should stop eating foods that inhibit thyroid hormone production.
When diet is not a cause, some people may be given thyroid hormone replacement with l-thyroxine. This drug blocks production of TSH and may shrink the goiter.
People with very large goiters may need surgery to remove part of the thyroid or may be given radioactive iodine to shrink the gland enough to prevent interference with breathing or swallowing or to correct cosmetic problems.
Last full review/revision May 2012 by Jerome M. Hershman, MD