Autoimmune diseases of the thyroid gland are considered to be the most frequent cause of thyroid gland disorders. Autoimmune thyroid diseases consist of two subgroups: autoimmune thyroiditis (AIT) and Graves' disease. The AIT is the most common human autoimmune disease. Infiltration of the thyroid gland with cytotoxic TaEurocells can lead to an initial thyrotoxicosis und during the course to hypothyroidism due to destruction of the thyroid gland. Substitution with Levothyroxine is indicated for manifest hypothyroidism and subclinical hypothyroidism with increased thyroid antibodies with the intention of normalizing the serum thyroid stimulating hormone (TSH). Graves' disease is characterized by the appearance of stimulating TSH receptor antibodies leading to hyperthyroidism. Endocrine ophthalmopathy may also occur. Ablative therapy with radioiodine therapy or thyroidectomy is administered to patients with Graves' disease without remission after at least 1 year of antithyroid drug therapy.