Hyperthyroidism

A 28-year-old man with newly diagnosed Graves' disease is counseled about treatment options. His physician discusses antithyroid drugs, radioactive iodine, and thyroidectomy. Which of the following statements about the management of Graves' disease is NOT correct?

A 32-year-old woman presents with palpitations, tremor, and heat intolerance for 3 weeks. Physical examination reveals a diffuse goiter, tachycardia (HR 110/min), and warm skin. TSH is suppressed at <0.01 mIU/L. What is the investigation of choice to confirm the diagnosis of Graves' disease?

A 32-year-old woman presents to the outpatient clinic with a 3-month history of palpitations, heat intolerance, and weight loss despite good appetite. She reports tremor in her hands and anxiety. On examination, she is tachycardic (HR 110/min), has a fine tremor, warm moist skin, and a diffusely enlarged thyroid gland without nodules. Her eyes appear prominent with lid lag noted. Laboratory investigations show: TSH 0.01 mIU/L (normal 0.4–4.0), free T4 18 pg/dL (normal 8–11), free T3 5.2 pg/dL (normal 2.3–4.2). Thyroid peroxidase (TPO) antibodies are positive. What is the most likely diagnosis?

A 28-year-old woman who is 8 weeks pregnant presents with palpitations, tremor, and anxiety. She has a history of Graves' disease diagnosed 2 years ago and was treated with radioactive iodine (RAI) 18 months ago. She has been euthyroid since then. Current thyroid function tests show: TSH 0.05 mIU/L (normal 0.4–4.0), free T4 14 pg/dL (normal 8–11), free T3 4.8 pg/dL (normal 2.3–4.2). Thyroid receptor antibodies (TRAb) are positive at high titer (8.5 IU/L; normal <1.75). She is not currently on any antithyroid medication. What is the most appropriate next step in management?

In Graves' disease, which immunoglobulin subclass is responsible for TSH receptor stimulation and the induction of exophthalmos?