What Is a Goiter?
A goiter is an enlarged thyroid gland. Thanks to the introduction of iodized salt in the 1920s, goiters have become much less common in North America than they once were. But goiters can still occur as the result of conditions other than iodine deficiency.
Diffuse goiters are smooth and uniformly large.
Nodular or multinodular goiters are lumpy and characterized by the presence of one or more nodules.
Toxic goiters, sometimes called thyrotoxic goiters, are those that occur with hyperthyroidism.
Nontoxic goiters are those that do not involve abnormalities in thyroid hormone production or malignancy.
Toxic multinodular goiters comprise numerous nodules and cause hyperthyroidism.
Sporadic nontoxic goiters occur in people with healthy thyroid function. The goiter may be diffuse, nodular, or multinodular.
Worldwide, the primary cause of goiter is iodine deficiency. Iodine, as you know by now, is a critical ingredient in the production of thyroid hormone. According to the Thyroid Foundation of America, nearly a quarter of the world's population do not get enough iodine in their diets. For these people, large goiters are common and often occur with nodules and severe hypothyroidism.
Without enough iodine, your thyroid works extra hard to make the thyroid hormone that your body needs. This added effort causes the thyroid gland to get bigger.
The International Council for the Control of Iodine Deficiency Disorders (ICCIDD) was created in 1985 for the sole purpose of achieving optimal iodine nutrition worldwide. The goal of eliminating iodine deficiency is done primarily through universal salt iodization. Currently, about 70 percent of households worldwide consume iodized salt. And countries such as China, Thailand, and Peru that were previously iodine deficient are significantly improved. Regions of the world that are still lagging include Central Asia and Africa.
Although the introduction of iodized salt in the United States has significantly lowered the incidence of goiter caused by iodine deficiency in this country, goiters still occur. In some cases, albeit much less commonly, goiters can be caused by excess iodine in the diet.
Goiters are also caused by hypo- and hyperthyroidism. In people with underactive thyroids, inadequate amounts of thyroid hormone cause TSH levels to go up, spurring the development of a goiter. In the United States, goiters associated with hypothyroidism are most often caused by Hashimoto's disease. Goiters may also be the result of an overactive thyroid brought on by Graves' disease, which causes the gland to swell and enlarge.
In people who develop toxic multinodular goiters, the progression of disease usually follows a common course. It typically starts when someone from an iodine-deficient area develops a goiter. Over time, nodules begin to form in the goiter. Eventually, one or more nodules becomes autonomous, and toxic multinodular goiter develops.
These events may take decades to unfold, which is why toxic multinodular goiter is more common in older patients. You are also more likely to get toxic multinodular goiters if you move from an iodine-deficient region, like the mountainous areas of Mexico, to an iodine-sufficient place like the United States. The shock of eating iodine-rich foods after years of not having enough iodine causes nodules to become autonomous and produce their own thyroid hormone.
In some cases, a goiter can simply occur on its own, in the absence of any malfunction of the thyroid gland. These are sometimes called euthyroid goiters. Some people develop a goiter when they have thyroiditis, inflammation of the thyroid gland.