Hashimoto disease is a representative organ-specific autoimmune disease. It occurs very frequently in middle-aged women. Generally, the symptom is only diffuse and elastic hard goiters detected by careful plpation. Immunological tests frequently reveal anti-thyroglobulin antibody and anti-TPO antibody. Hypothyroidism develops in some patient along with progression of the disease. In some patient, on the other hand, a condition called destructive thyroiditis may develop during the course of the disease, in which the thyroid gland is transiently destroyed, accompanied by thyrotoxic state. In this state, namely painless thyroiditis, 123I-uptake ratio is extremely low and TSH-receptor antibody is generally not observed. The thyroid hormone is administered to patient with large goiter or hypothyroidism, and antiphlogistic analgesics or adrenocortical hormone with beta-blockers in case of destructive thyroiditis.