Hyperthyroidism occurs in 0.2–0.7% of pregnancies with the large majority due to Graves’ disease. Graves’ disease is an autoimmune condition where TSH-receptor antibodies stimulate the thyroid gland, leading to increased thyroid hormone and decreased TSH via negative feedback loop. Screening for thyroid disease is indicated in pregnant persons with personal or family history of thyroid disease, history of type 1 diabetes, or clinical features suspicious for thyroid disease. Hyperthyroidism in pregnancy is diagnosed by a low TSH and a high T4 or T3, based on trimester-specific and population-based reference ranges. Treatment is traditionally with PTU given in the first trimester to reduce risk of embryopathy and methimazole in the second and third trimester to reduce the risk of hepatotoxicity, but variation in practice exists. Thyroid hormone, not TSH, should be monitored every 2 to 4 weeks with the goal to keep T4 or T3 slightly above or within the high-normal reference range. While rare, thyroid storm is a potentially life-threatening condition requiring immediate recognition and management in a tertiary care setting.