Thyrotoxicosis beta-blockers

Beta blockers without intrinsic sympathomimetic activity (eg, metoprolol, propranolol, atenolol) are effective therapeutic adjuncts in the management of thyrotoxicosis since many of these symptoms mimic those associated with sympathetic stimulation. Propranolol has been the 3 blocker most widely studied and used in the therapy of thyrotoxicosis. Beta blockers cause clinical improvement of hyperthyroid symptoms but do not typically alter thyroid hormone levels. Propranolol at doses greater than 160 mg/d may also reduce T3 levels approximately 20% by inhibiting the peripheral conversion of T4 to T3. 

As the symptoms of hyperthyroidism mimic in many aspects those of sympathic stimulation propranolol, and probably also other non-selective beta blockers (see Chapter 20), give rapid relieve in thyrotoxicosis while having no effect on the underlying disease. 

Beta blockers without intrinsic sympathomimetic activity are effective therapeutic adjuncts in the management of thyrotoxicosis since many of these symptoms mimic those associated with... 

Some patients with thyrotoxicosis have occult cardiac dysfunction. However, the use of beta-blockers in the treatment of thyrotoxicosis can have severe consequences in terms of severe cardiac dysfunction (10). 

Answer E. Increased sympathetic activity is a major problem in hyperthyroidism and is best managed by use of beta blockers, which can offset cardiac stimulatory effects. Propranolol has an ancillary action in thyrotoxicosis in that it prevents conversion of T4 to T3 via its inhibition of 5 deiodinase. Amiodarone causes difficult-to-predict adverse effects on thyroid function and would not be appropriate in a patient with hyperthyroidism. Bretylium is an IV agent reserved for ventricular arrhythmias. Digoxin is not ideal because of its complex actions on the heart, which include both inhibition and stimulation. 

E. Other Drugs Other agents used in the treatment of thyrotoxicosis include the beta-blockers. Propranolol also inhibits 5 -deiodinase. These agents are particularly useful in controlling the tachycardia and other cardiac abnormalities of severe thyrotoxicosis. 

The major therapies available for Graves disease are surgery, thyroid-suppressant drugs, and radioactive iodine in sufficient dosage to destroy the gland. Ipodate—an iodine-containing x-ray contrast material—and beta-blockers are of value in severe thyrotoxicosis. 

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