What disease occurs due to an enlargement of the thyroid gland?

The disease characterized by an enlargement of the thyroid gland is goiter. A goiter refers to the visible swelling or enlargement of the thyroid gland, which can result from a variety of conditions including iodine deficiency, autoimmune diseases, or nodular growths. When the thyroid enlarges, it can be due to either overproduction or underproduction of thyroid hormones, or simply an increase in the size of the gland itself without necessarily implicating hormone levels.

In contrast, hypothyroidism indicates an underactive thyroid that does not produce sufficient hormones, but it does not inherently involve the enlargement of the gland. Similarly, Graves' disease is an autoimmune hyperthyroid condition that often presents with goiter due to overstimulation of the thyroid, yet the term "goiter" specifically describes the enlargement itself, which can occur with or without hyperthyroidism. Hashimoto's thyroiditis, also an autoimmune condition, typically leads to hypothyroidism and can cause goiter as a secondary outcome, but in this context, the primary designation of enlarged thyroid is still specifically identified as goiter. Therefore, goiter is the most accurate answer for the condition characterized primarily by thyroid gland enlargement.