Subacute lymphocytic thyroiditis is also known as painless thyroiditis (PPT) and silent thyroiditis. There are two types of the disease: sporadic thyroiditis and postpartum thyroiditis. The incidence of PPT has been reported to be 5-10% in women aged 30-40 years. 33-55% of women with positive antibodies in the first trimester of pregnancy have PPT. family history of thyroid disease, smoking, high titers of antibodies, and delivery of female babies have a high incidence. PPT is the most common cause of “hyperthyroidism” in postpartum women, accounting for 70-80%. 1. Clinical manifestations The incidence of this disease has been increasing in recent years, and 2/3 of them are women aged 30-40. The main manifestation is mild to moderate “hyperthyroidism”, which may include palpitations, fear of heat, excessive sweating, fatigue, weight loss, etc. The thyroid gland is mildly enlarged or normal in size, but there is no endocrine synostosis or anterior tibial mucus edema, and the thyroid gland lacks vascular murmurs. The duration of “hyperthyroidism” does not exceed 3 months and is often followed by hypothyroidism, with a few becoming permanently hypothyroid. 2. Laboratory tests: Destruction of thyroid follicles, elevation of T3 and T4 in blood, mild to moderate elevation of TGA and TMA in 80% of postnatal and 50% of epidemic cases. Blood sedimentation is normal or mildly elevated. Ultrasound shows diffuse or focal hypoechogenicity. Thyroid iodine uptake is decreased. A thyroid puncture biopsy showing diffuse or focal lymphocytic infiltration is diagnostic of the disease. The duration of hyperthyroidism does not exceed 3 months and is often followed by hypothyroidism, with a few becoming permanently hypothyroid. Differential diagnosis The disease is differentiated from subacute granulomatous thyroiditis, which has pain and tenderness, low recurrence rate, associated with viral infection, significantly increased sedimentation, and granulomatous changes on biopsy. 4. Treatment The treatment of this disease is symptomatic. Those with “hyperthyroidism” do not need special treatment, while those with significant symptoms can take oral beta-blockers and do not need to use antithyroid drugs.