A goiter is an abnormal swelling or enlargement of the thyroid gland, which sits at the front of your neck, just below your voice box. The thyroid is a small but important gland that helps control how your body uses energy, and when it grows larger than normal, it can create a visible bulge in the neck.

Goiters often develop when the body doesn't get enough iodine, a mineral found in seafood, dairy products, and iodized salt. Without sufficient iodine, the thyroid gland swells as it tries harder to do its job. In the early 1900s, goiters were common in parts of America far from the ocean, where people ate less seafood and got less iodine in their diets. These regions were sometimes called the “goiter belt.” The problem largely disappeared after 1924, when iodine started being added to table salt.

Today, goiters are rare in countries where iodized salt is common, but they still occur in parts of the world where iodine deficiency remains a problem. Goiters can also develop from other thyroid conditions. Most goiters are harmless, though large ones can make swallowing or breathing uncomfortable. Doctors can usually treat goiters with medication, dietary changes, or, in some cases, surgery.