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How can Hashimoto disease lead to goiter?

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immune system disorder False-color scanning electron micrograph of a T cell infected with HIV (human immunodeficiency virus), the agent that causes AIDS (acquired immunodeficiency syndrome).

In Hashimoto disease, the development of a goitre—an enlargement of the thyroid gland—is primarily driven by the body's autoimmune response.12

The condition involves the infiltration of the thyroid gland by lymphocytes, which are white blood cells that produce cytokines and other substances that damage thyroid cells. This inflammatory process, known as thyroiditis, leads to the gradual destruction of the gland and a decrease in thyroid hormone production.12

As the thyroid tissue is damaged, the gland often undergoes hyperplasia, or excess growth of thyroid tissue, which manifests as a symmetrical, rubbery enlargement. While the exact factors initiating this damage remain unknown, the resulting goitre is a hallmark of the disease's progression alongside the development of hypothyroidism. In some cases, treatment with thyroid hormone, such as thyroxine, may help reduce the size of the goitre.12