In Hashimoto's disease is an autoimmune disease characterized by inflammation and damage to the thyroid tissue. Damage occurs because the body's immune cells mistakenly attack the thyroid tissue. Thyroid tissue damaged by immunologic factors is replaced by lymphocytes, plasma cells and fibrosis. These patients have antithyroid antibodies directed against elements in the thyroid cell or colloid such as thyroglobulin or microsomes. These patients usually present with a firm, diffuse goitre. In some the gland is frankly nodular and then can also present as a solitary thyroid nodule. They are usually hypothyroid with a raised TSH level.
Hashimoto's disease is the most common cause of goitrous hypothyroidism in adults and sporadic goitre in children. It is 10 to 15 times more common in women than men. In the USA, about 25 percent of women over age 60 have Hashimoto's thyroiditis.