Postpartum thyroiditis is a type of autoimmune thyroiditis that occurs within 1 year after delivery in women who had normal thyroid function before pregnancy. Thyrotoxicosis in postpartum thyroiditis usually occurs 2 to 6 months after delivery and is due to destruction of thyroid tissue and leakage of thyroid hormones, which may resolve on its own. The hypothyroid phase of postpartum thyroiditis occurs 3 to 12 months postpartum, with 10% to 20% of patients regressing to permanent hypothyroidism. Postpartum thyroiditis reflects a rebound in the postpartum period of an immune system that has been relatively suppressed by pregnancy. Typical cases undergo 3 clinical phases, namely, thyrotoxicosis, hypothyroidism, and recovery. Patients with postpartum thyroiditis need to be seen by a medical professional.