An enlarged thyroid gland, swelling of the small gland at the base of the neck, is caused by many factors, some of which are serious, according to the Mayo Clinic. It occurs when the gland is producing too little or too much thyroid hormone. Benign thyroid nodules or cancer also make the thyroid swell. If left untreated, an enlarged thyroid can lead to serious complications.
Autoimmune Disease
An enlarged thyroid can signify autoimmune disease, which means the body's immune system attacks the thyroid by mistake. Hashimoto's disease is an autoimmune disease in which the damaged thyroid produces too little thyroid hormone, causing fatigue and weight gain, the Mayo Clinic says. In contrast, Grave's disease, autoimmune-directed overactivity of the thyroid, causes weight loss and irritability. If untreated, both can lead to heart problems.
Iodine Deficiency
An enlarged thyroid may indicate a lack of iodine in the diet, according to the Mayo Clinic. The thyroid enlarges because it is trying to get more iodine. Eating foods that inhibit thyroid hormone, such as cabbage, worsens the deficiency. This is common in developing countries but rare in the United States, because iodine is added to table salt.
Thyroid Cancer
A lump or enlargement on one side of the thyroid may indicate thyroid cancer, according to the Mayo Clinic. Thyroid cancer is rare, however, with only 37,000 new cases in the United States each year.
