Introduction Most common cause of hyperthyroidism An autoimmune disease with stimulating anti-TSH receptor antibodies a type II hypersensitivity anti-microsomal, anti-thyroglobulin antibodies also present Female dominant HLA-B8, Dr3 association Often incited during stress e.g. childbirth, infection, steroid withdrawal Presentation Symptoms heat intolerance weight loss hyperactive diarrhea hyperreflexia tachycardia, palpitations, arrhythmias thyroid hormone increases heart rate and contractility and decreases SVR warm moist skin and sweating hypertension Physical exam symmetrical, non-tender thyroid enlargement ophthalmopathy (proptosis, exophthalmos) due to glycosaminoglycan deposition pretibial myxedema digital swelling Evaluation Serology ↑ total serum T4 ↑ free T4 ↓ serum TSH diffusely ↑ 123I uptake Treatment Medical β-blockers thionamides result in reduced hormone synthesis PTU and methimazole discontinue if agranulocytosis occurs as these are side effects of these medications during pregnancy, first-line is propranolol, followed by propylthiouracil if these treatments do not work and symptoms are severe, thyroidectomy is the treatment of choice complications include recurrent laryngeal nerve injury hypocalcemia due to PTH gland removal resulting in the classic findings of hypocalcemia (tetany, QT prolongation, etc.) 131I ablation hypothyroidism may result contraindicated in pregnancy may cause transient worsening of exophtalmos or hyperthyroid symptoms due to release of thyroid hormone with thyroid cell destruction prevention: pretreatment with glucocorticoids Prognosis, Prevention, and Complications Stress-induced catecholamine surge may be fatal by arrhythmia Pregnancy complications anti-TSH receptor antibodies may cross placenta and produce hyperthyroidism in the fetus