Which condition involves the swelling of the thyroid gland?

The condition that specifically involves the swelling of the thyroid gland is goiter. A goiter is characterized by an enlargement of the thyroid gland, which can occur in various circumstances, such as iodine deficiency, autoimmune diseases, or the presence of nodules. This enlargement can affect the gland’s function, potentially leading to conditions like hypothyroidism or hyperthyroidism; however, it is fundamentally defined by the physical swelling itself.

While other conditions listed can involve thyroid dysfunction or inflammation, they do not inherently describe the swelling of the gland as their primary feature. For instance, hypothyroidism relates to insufficient thyroid hormone production, thyroiditis denotes inflammation of the thyroid (which may or may not lead to swelling), and Graves' disease, an autoimmune disorder, primarily causes hyperthyroidism but can also result in a goiter due to the overstimulation of the gland. Thus, goiter is the most direct answer to describe the condition of thyroid swelling.