Treatment of overt hyperthyroidism

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Patients with overt hyperthyroidism from Graves' disease or from toxic mul-tinodular goiter should clearly be treated. One therapeutic option for patients with Graves' disease is medical management with methimazole (MMI) or pro-pylthiouracil (PTU), both of which decrease thyroid hormone synthesis. Therapy with one of these drugs will induce long-term remission of Graves' disease in about half of all patients, although those patients with large goiters are less likely to remain euthyroid (70). Since remission of the hyperthyroidism caused by toxic multinodular goiter almost never occurs, therapy with MMI or PTU is only given prior to definitive therapy, as described below. Side effects of both of these medications include rash or urticaria. More seriously, agranulocytosis occurs in approximately 0.3% of patients (71). Patients starting on these medications should be cautioned to discontinue them and call their physician if they develop fever, rash, jaundice, arthralgia, or sore throat.

More definitive therapy with radioactive iodine may also be elected, especially in older patients. After radioactive iodine treatment, patients may become transiently more thyrotoxic owing to damage to the gland and release of stored hormone. Pretreatment with antithyroid medications may help protect older patients or others at risk for cardiac complications by decreasing thyroid hormone stores (71), although this concept has recently been challenged (72,73). Most patients will become euthyroid within weeks after receiving a single large dose of radioiodine; the remaining 10-20% of patients require retreatment 6 mo to a year later. Within a year of treatment, up to 90% of patients will become hypothyroid; the other 10% become hypothyroid at a rate of 2-3% per year (70).

Surgery is another option for treatment of younger patients with hyperthyroidism. It is especially useful for patients with very large goiters and/or compressive symptoms who often require multiple doses of 131I. Subtotal or near-total thyroidectomy is the procedure of choice. The most common adverse effects of thyroidectomy are injury to the parathyroids, resulting in hypocalcemia, and injury to the recurrent laryngeal nerve. Patients should be treated with antithyroid drugs to restore euthyroidism preoperatively. Additionally, they should receive iodine for 7-10 d before surgery to decrease thyroid blood flow. When a patient with a large goiter is noncompliant with medical therapy and thyroidectomy is planned, euthyroidism can be achieved in 5-7 d by a regimen similar to that employed in some patients with thyroid storm. Large doses of PTU or MMI decrease hormone synthesis. One milligram of dexamethasone twice a day decreases peripheral conversion of T4 to T3 by inhibiting the outer ring 5'-deiodinase. The iodine-rich contrast agent iopanoic acid (0.5 g twice a day) decreases T4 to T3 generation, release of hormone from the gland, and thyroid blood flow. A p-blocker decreases the catecholamine effects of thyrotoxicosis. All these medications are given, under careful supervision, at home or preferably in the hospital (74).

P-Blockers can be used as adjunctive treatment to slow the heart rate and improve symptoms of anxiety, tremor, palpitations, heat intolerance, and tremor. P-blockade should be used as primary therapy only in patients with transient thyrotoxicosis secondary to thyroiditis and a low thyroid RAIU (71).

Once patients become biochemically euthyroid, symptoms of hyperthyroid-ism should resolve within a few weeks. Patients with atrial fibrillation in the setting of hyperthyroidism will often spontaneously convert to sinus rhythm once the hyperthyroidism has been corrected, generally within 4 mo of normalization of serum T3 and T4 concentrations (75).

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