It is an uncommon inflammation of the thyroid gland, and when the diagnosis is made the patient is unheard of and looks puzzled and bewildered. It is most often caused by a decrease in the immunity of the body after an upper respiratory tract infection (viral or bacterial), which develops further, just like viral myocarditis in individual patients after an upper respiratory tract infection. The exact pathogenesis remains unclear. The disease may manifest as a painful nodule in the front of the neck, which may start on one side and gradually spread to the other side. The pain may spread to the ipsilateral face and head, and may be obvious when the neck is turned or swallowed in severe cases, so that one dare not touch it. It may be accompanied by low or moderate fever, and may have symptoms of hyperthyroidism such as panic, excessive sweating, weight loss, fatigue, and weakness. The disease is easily misdiagnosed as a thyroid tumor, etc., or even surgery when seen after irregular treatment, so a differential diagnosis is needed. The diagnosis must be confirmed with special tests such as iodine uptake rate, thyroid function, blood count and sedimentation, and thyroid scan. If necessary, thyroid aspiration histocytology is required. The treatment of the disease often takes about 3 months. The disease can recur when the body’s resistance decreases (e.g., after an upper sensation). Individuals can be chronic, with a delay of more than 1 year. Most people recover completely from the disease, while a few may remain permanently hypothyroid, in which case lifelong thyroxine replacement therapy is required.