Hashimoto thyroiditis is an autoimmune disease that destroys thyroid follicular cells through cell- and antibody-mediated immune processes. This聽disease is also known as chronic autoimmune thyroiditis and chronic lymphocytic thyroiditis. Hashimoto thyroiditis is the most common cause of hypothyroidism in developed countries. The pathophysiology of this disease involves the formation of antithyroid antibodies and T-cell activation that attack the thyroid tissue, causing progressive fibrosis. Together with Graves disease, this condition comes in the category of autoimmune thyroid disorders.聽This condition was initially described by a Japanese physician, Haruto Hashimoto, in 1912 as "struma lymphomatosa" after he found enlarged thyroids having lymphocytic infiltration. Women are more聽commonly affected. The female-to-male ratio is at least 7 to 10:1.聽The incidence of Hashimoto thyroiditis increases with age, with most cases found between ages 45 and 55 years. The incidence tends to be higher in countries with a lower prevalence of iodine deficiency.聽Hashimoto thyroiditis can occur alone, or it can occur as a part of autoimmune polyglandular syndrome (APS).聽Some individuals with Graves disease聽might transform into Hashimoto thyroiditis and vice versa. This could indicate a common pathogenesis for these disorders but different clinical presentations.
