Thyroiditis, clinically more commonly seen as subacute thyroiditis, is primarily caused by viral infections. The main clinical symptoms include pain in the anterior neck accompanied by fever, typically in the afternoon or evening. Upon examination, the thyroid is enlarged and tender. In terms of auxiliary examinations, blood tests reveal that some patients may have elevated white blood cells if there is a concurrent infection, and an increased erythrocyte sedimentation rate. Furthermore, initially, there might be mild signs of hyperthyroidism. Thyroid ultrasound may suggest signs of subacute thyroiditis, and the iodine uptake rate is decreased. If further examination is desired, a fine needle aspiration of the thyroid can be performed to help comprehensively consider and confirm the diagnosis.