This condition is named after Dr. Hakaru Hashimoto who first described it in 1912. Hashimoto's thyroiditis is an organ specific autoimmune disease. This chronic inflammatory glandular autoimmune disease develops when the immune system attacks protein expressed on the surface of the thyroid gland. It is characterized by infiltration of the thyroid gland by lymphocytes causing gradual destruction of the gland. Hashimoto's thyroiditis patients have positive serum antibody titres to thyroperoxidase, while thyroglobulin antibodies are positive in approximately half of the patients. When both tests are used, approximately 95% of patients are detected with the disease.
Hashimoto's thyroiditis is the most common cause of thyroiditis, and as in the case with other autoimmune disorders, more common among middle aged women. The onset of the disease is slow, and it may take months or even years for the condition to be detected. Enlargement of the thyroid gland, local tenderness and thyroid function disorder are the common clinical features of the disease. Hashimoto's thyroiditis accounts for many of the enlarged thyroids formerly designated as adolescent or simple goiter.
The incidence of Hashimoto's thyroiditis seen in practice is unknown but is roughly equal to that of Graves' disease (on the order of 0.3 - 1.5 cases per 1,000 population per year). It is estimated to affect between 0.1% and 5% of all adults in Western countries. The disease is 15-20 times as frequent in women as in men. It occurs especially during the decades from 30 to 50, but may be seen in any age group, including children.
It is not uncommon for patients with autoimmune thyroid disease to have other coinciding autoimmune disorders. Approximately 25 percent of patients with Hashimoto's thyroiditis may develop pernicious anemia, diabetes, adrenal insufficiency, or other autoimmune diseases.
There is evidence of a genetic predisposition in the development of Hashimoto's thyroiditis. Hashimoto's thyroiditis is reported to occur in two forms: an atrophic variety, perhaps associated with HLA-DR3 gene inheritance, and a goitrous form associated with HLA-DR5.