Chronic lymphocytic thyroiditis, also known as Hashimoto’s thyroiditis, is a form of autoimmune thyroiditis that is often insidious and unrecognized, and is sometimes detected by chance during physical examinations or by consultation when signs and symptoms of hypothyroidism are present. The cause of Hashimoto’s thyroiditis is thought to be the result of an interaction between genetic factors and a variety of internal and external environmental factors. The disease is frequently found in several generations of the same family. the HLA gene partially determines the genetic susceptibility, but this role is not very strong and varies somewhat between populations. Infection and dietary iodide are two environmental factors in the development of Hashimoto’s thyroiditis. Epidemiological studies have found a high incidence of Hashimoto’s thyroiditis in both iodine deficient and enriched areas, and experimental studies have also shown that excess iodine can cause thyroiditis in genetically susceptible experimental animals. The pathogenesis of Hashimoto’s thyroiditis is based on a defective immune regulation, in which both cellular and humoral immunity are involved in damaging the thyroid gland, and in which there is a large infiltration of lymphocytes and plasma cells in the thyroid tissue. Direct killing of target cells by sensitized lymphocytes. The disease is often associated with other autoimmune diseases such as addison, pernicious anemia, dry syndrome, and SLE. Hashimoto’s thyroiditis does not have typical clinical symptoms and can be easily confused with other types of thyroiditis and other diseases. Clinical diagnosis requires the use of ancillary tests, and early detection is possible with regular checkups in people with a family history.