A 40-year-old, previously healthy woman comes to the office due to a 3-month history of progressive weakness, frequent insomnia, palpitations, and an unintentional 4-kg (8.8-lb) weight loss. She also has a constant feeling of anxiety and increased sensitivity to warm temperatures. Blood pressure is 140/70 mm Hg and pulse is 110/min. Physical examination shows lid lag without exophthalmos and a fine tremor of the patient's outstretched hands. The thyroid gland is enlarged and nontender. Laboratory results are as follows: Treatment options are discussed with the patient, and she elects to proceed with radioiodine therapy. Which of the following is the most likely outcome after treatment in this patient?

Question

A 40-year-old, previously healthy woman comes to the office due to a 3-month history of progressive weakness, frequent insomnia, palpitations, and an unintentional 4-kg (8.8-lb) weight loss.  She also has a constant feeling of anxiety and increased sensitivity to warm temperatures.  Blood pressure is 140/70 mm Hg and pulse is 110/min.  Physical examination shows lid lag without exophthalmos and a fine tremor of the patient's outstretched hands.  The thyroid gland is enlarged and nontender.  Laboratory results are as follows:  Treatment options are discussed with the patient, and she elects to proceed with radioiodine therapy.  Which of the following is the most likely outcome after treatment in this patient?

Quizplus · Accepted Answer

11ec25c8_d3cc_21a3_bc81_2dc9520a7770_MD0003_00 This patient has symptomatic hyperthyroidism (low TSH and elevated T4 levels) associated with an elevated titer of thyroid-stimulating immunoglobulins, consistent with Graves disease. The 3 primary treatment options in Graves disease include radioactive iodine (RAI) therapy, antithyroid drugs, and surgical thyroidectomy. RAI (¹³¹I) is taken up by the thyroid follicular cells in a manner similar to that of natural iodine, and the subsequent beta emission induces slow necrosis of the thyroid follicular cells. This leads to clinical and biochemical resolution of hyperthyroidism over the subsequent 6-18 weeks (not rapidly) (Choice E). ¹³¹ The goal of RAI in Graves disease is to administer a sufficient dose of radiation to prevent recurrence of hyperthyroidism. However, the diffuse uptake of radioiodine eventually leads to permanent hypothyroidism within months in >90% of patients. In contrast, when RAI is used to treat toxic nodular goiter and toxic adenoma, the radioisotope is taken up only by the autonomous thyroid tissue, and the function of the remaining normal tissue is usually adequate to prevent permanent hypothyroidism. (Choice B) RAI can acutely worsen Graves ophthalmopathy due to increased titers of thyroid-stimulating immunoglobulins (autoantibodies). Thyroidectomy is preferred in those with significant ocular manifestations. (Choice C) There is no significant increased risk of thyroid cancer or overall cancer mortality in patients treated with RAI for Graves disease. (Choice D) Pharmacologic doses of iodine (eg, in potassium iodide solutions) are occasionally used to transiently reduce the synthesis and release of thyroid hormones in patients with Graves disease. In contrast, the dose of iodine used in RAI, although sufficient to induce radiation necrosis, is much lower than that required to biochemically inhibit thyroid hormone synthesis. (Choice F) Thyroid hormone increases sensitivity to catecholamines, and many of the symptoms of hyperthyroidism are mediated by the resulting hyperadrenergic state. Beta blockers can be used to blunt these symptoms without altering thyroid hormone levels, but RAI therapy drastically decreases hormone production. Educational objective: Radioiodine therapy for Graves disease leads to resolution of hyperthyroidism in 6-18 weeks, but the dose needed for treatment gradually leads to permanent hypothyroidism in most patients. This therapy can also acutely worsen Graves ophthalmopathy due to increased titers of thyroid-stimulating autoantibodies. References: Hyperthyroidism and other causes of thyrotoxicosis: management guidelines of the American Thyroid Association and American Association of Clinical Endocrinologists. (http://www.ncbi.nlm.nih.gov/pubmed/21510801) Radioiodine therapy for hyperthyroidism. (http://www.ncbi.nlm.nih.gov/pubmed/21306240)

A 40-Year-Old, Previously Healthy Woman Comes to the Office Due