A goiter is an enlargement or hyperplasia of the thyroid gland. A simple goiter is any thyroid enlargement that is not caused by an infection or neoplasm and that does not result from another hypothyroid or hyperthyroid disorder. It is classified as endemic or sporadic. Endemic or colloid goiter is the result of insufficient dietary intake of iodine. Sporadic or nontoxic goiter follows ingestion of certain drugs or food. Simple goiter is more common in women, especially during adolescence, pregnancy, and menopause. During these times, the body’s demand for thyroid hormone is increased.
The thyroid gland hyperplasia that characterizes a goiter occurs when the thyroid gland cannot secrete sufficient levels of the two iodine-rich hormones: thyroxine (T4) and triiodothyronine (T3). The thyroid gland tissue enlarges to compensate for the deficiency. In simple goiter, the inadequate secretion of these thyroid hormones may be caused by a dietary iodine deficiency, the ingestion of substances known to induce goiter (goitrogens), or some error in the hormone formation process within the thyroid gland. Risk factors include being female, over age 40, and having a family history of goiter. In many cases, though, the condition is idiopathic.
Signs and Symptoms
The extent of thyroid enlargement varies from case to case. A simple goiter may appear as a small nodule, or it can be quite massive, presenting a conspicuous swollen mass at the front of the neck, just above the sternum. The goiter shown in Figure is more commonly seen in countries that, unlike the United States, do not put iodized salt in foods. The goiter may compress the esophagus or trachea, producing dysphagia, dyspnea, dizziness, and syncope.
FIGURE. Haitian woman with nontoxic goiter. ( James Gray, MissionFoto, Gosport, IN.)
A thorough history and physical examination to rule out disorders with similar clinical effects, such as Graves disease and Hashimoto thyroiditis, is necessary. Diagnosis of simple goiter is made on the basis of thyroid gland enlargement in the presence of normal levels of T3 and T4 hormones. A T3 and T4 radioimmunoassay test accurately measures the levels of these two hormones. If an ultrasound locates any nodules, a biopsy is necessary to check for thyroid cancer.
The treatment goal is to reduce the size of the goiter. How this is accomplished depends in part on the underlying cause of the condition. Treatment procedures may include dietary supplements of iodine or T3 and T4 hormone replacement therapy. Sporadic goiter requires avoidance of known goitrogenic foods and drugs. A large goiter that is unresponsive to therapy may require excision, resulting in lifelong thyroid replacement therapy.
Nutritional supplements may be helpful. A diet that includes iodized salt but that avoids goitrogenic foods is recommended; those foods include rutabagas, cabbage, peas, spinach, radishes, soybeans, peanuts, peaches, and pears, all which contain agents that decrease T4 production.
Iodized salt should be used to supply the daily 150 to 300 mg of iodine necessary to prevent goiters. Measuring the neck circumference to monitor for progressive thyroid enlargement may be beneficial.
The prognosis is generally good following effective treatment. Complications from severe cases of simple goiter include tachycardia, congestive heart failure, and atrial fibrillation.
Prevention of simple goiter includes adequate dietary intake of iodine.