Subacute thyroiditis is an inflammatory disease of the thyroid gland. The main clinical symptoms are enlargement of the thyroid gland with pain, elevated body temperature, and in severe cases, systemic symptoms such as chills, fever, sore throat, swelling and pain in the front of the neck, dry mouth, and irritability. The age of onset of subarachnoiditis is mostly seen in young and middle-aged women aged 30-50, with the incidence in women being 3-6 times higher than that in men. It is now believed that subarachnoiditis is mainly related to viral infection. The disease is often accompanied by flu-like symptoms 1-2 weeks before the onset of the disease, early manifestations of fever, sore throat and other symptoms of upper respiratory tract infection, accompanied by weakness, loss of appetite, later may appear swelling of the thyroid area with pain, and radiating pain. A typical case of subthyroiditis can be divided into an early stage with hyperthyroidism, a middle stage with occasional hypothyroidism, and a recovery stage. In the early stage, symptoms similar to upper respiratory tract infection first appear, followed by pain and pressure in the thyroid gland, often radiating to the forehead, behind the ears, front of the neck, occiput, anterior chest, shoulders, etc. Within a week of the disease, about 50% of patients may have hyperthyroidism, such as fear of heat, excessive sweating, panic, and hand tremors. In the middle stage, hypothyroidism such as fear of cold, drowsiness, weakness and swelling may occasionally appear. In the recovery period, the symptoms may gradually improve, and if the treatment is timely, the patient’s symptoms may be completely relieved, and rarely remain as permanent hypothyroidism. Subthyroiditis is easily misdiagnosed because the early symptoms are not typical. When patients have mainly hyperthyroid symptoms such as fear of heat, excessive sweating, and panic, but mild thyroid pain, they are easily misdiagnosed as hyperthyroidism; in addition, there are cases where the swelling in front of the neck is obvious, hard or nodular and often misdiagnosed as thyroid adenoma. Therefore, when anti-infection treatment and anti-hyperthyroidism treatment are ineffective, the possibility of subacute thyroiditis should be considered first. To prevent misdiagnosis, doctors should take a detailed medical history, conduct a comprehensive physical examination, focusing on the main thyroid gland, and inform the patient to improve laboratory tests, such as thyroid function may show normal or elevated FT3 and FT4, normal or reduced TSH, significantly reduced iodine uptake by the thyroid gland, and significantly increased blood sedimentation; thyroid nuclear scan may show cold nodules. The treatment of milder cases can be treated with non-steroidal anti-inflammatory drugs such as anti-inflammatory pain (indomethacin tablets); for more severe cases or unsatisfactory treatment with the above drugs, adrenal glucocorticoid therapy can be used, which has a significant effect on the disease. After several weeks or months of treatment, the blood sedimentation and thyroid function can return to normal, and the thyroid mass can disappear. The disease is self-limiting and has a good prognosis, with the vast majority of patients recovering without any residual problems. However, the disease has a certain degree of recurrence, especially after the patient reduces or stops the medication by himself, but after the recurrence, the treatment with the above drugs is still effective.