We generally refer to acute thyroiditis as an acute suppurative thyroiditis, which is a type of purulent infectious disease, often caused by a mixed bacterial infection, such as staphylococcus, streptococcus, gram-negative bacilli, and anaerobes, etc. Patients with compromised or deficient immune functions, such as those with AIDS, leukemia, diabetes, can also have infections like fungi and pneumocystis. Some thyroid nodules, due to events like necrosis or cystic changes from punctures, can also cause a suppurative infection, and this condition is generally common among middle-aged and elderly patients. Therefore, the main cause of acute thyroiditis is mostly due to infections.