Postpartum thyroiditis (PPT) is a subacute autoimmune thyroiditis that occurs in the postpartum period. It differs from chronic lymphatic thyroiditis (HT) in that it occurs in the postpartum period and has a self-limiting course, with a light lymphatic infiltration of the thyroid gland and no germinal center formation. Clinical manifestations] 1. Hyperthyroidism; a transient hyperthyroidism occurs 6 weeks to 6 months after delivery and usually lasts 2 to 4 months. It occurs due to inflammatory cell damage of the thyroid gland and leakage of thyroid hormones from the thyroid follicles into the circulation, resulting in increased serum thyroid hormone levels, decreased serum TSH, and manifestations of thyrotoxicosis. 2. Hypothyroidism; usually lasts from 1 to 3 months. At this time, the hormones in the thyroid follicles have been leaked out, and the damaged thyroid cells cannot produce enough hormones, so hypothyroidism occurs. 3, recovery period; after self-repair, thyroid cell function is restored, sufficient hormones are produced, and thyroid function returns to normal. About 26% of patients have three stages of performance, 38% of patients have only hyperthyroidism, and 36% of patients have only hypothyroidism. Some patients have mild to moderate enlargement of the thyroid gland with moderate texture, but no tenderness. Laboratory tests] Serum FT3, FT4, levels and iodine-131 uptake rates show a similar separation curve to subacute thyroiditis. Most patients were positive for TPOAB. The diagnosis is based on 1) no history of abnormal thyroid function before and during pregnancy; 2) abnormal thyroid function (hyper, hypo or both) occurring within one year after delivery; 3) reduced iodine 131 uptake during the hyperthyroid phase; 4) negative serum TRAB, and the diagnosis of postpartum thyroiditis (PPT) can be established. Treatment prognosis] The hyperthyroid phase presents a self-recurring process, generally without antithyroid drugs, and symptomatic treatment with B-blockers can be given for severe symptoms. In the hypothyroid phase, replacement therapy with eugenol can be given. Thyroid function monitoring should be checked regularly and lifelong replacement therapy should be given to patients with permanent hypothyroidism.