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Chapter 62. Thyroid Disorders

Dr. M wants to know which antithyroid medication would be preferred in a 29-year-old, nonpregnant woman with thyrotoxicosis (without thyroid storm) and why. What is your response?

a. Propylthiouracil is preferred due to fewer side effects and less frequent dosing.

b. Methimazole is preferred due to fewer side effects and less frequent dosing.

c. Methimazole is preferred since it blocks the peripheral conversion of T4 to T3.

d. Propylthiouracil is preferred since it blocks the peripheral conversion of T4 to T3.

Answer b is correct. Methimazole does not produce side effects such as vasculitis and hepatotoxicity. Methimazole can also be dosed once daily.

Answer a is incorrect. Propylthiouracil has a higher incidence of serious side effects such as vasculitis and hepatotoxicity. Propylthiouracil must also be dosed multiple times a day.

Answer c is incorrect. Methimazole does not block the peripheral conversion of T4 to T3.

Answer d is incorrect. Propylthiouracil does block the peripheral conversion of T4 to T3 but this does not offer any additional benefit except in thyroid storm.

LR is a 32-year-old woman who is still experiencing symptoms of hyperthyroidism, including tremor and tachycardia, despite treatment with methimazole. Which medication can be added to provide additional symptomatic relief?

a. Nifedipine

b. Prednisone

c. Propranolol

d. Ibuprofen

Answer a is incorrect. Certain calcium channel blockers (nondihydropyridine calcium channel blockers such as verapamil and diltiazem) may be used to decrease the heart rate in patients with hyperthyroidism. Dihydropyridine calcium channel blockers such as nifedipine, amlodipine, and felodipine do not slow the heart and may actually cause a reflex tachycardia, worsening hyperthyroidism symptoms.

Answer b is incorrect. Prednisone may be used to treat patients presenting in thyroid storm but has no additional symptomatic benefit for the outpatient treatment of hyperthyroidism.

Answer c is correct. β-Adrenergic blocking agents will slow the heart rate to help correct tachycardia and may improve other symptoms of hyperthyroidism including anxiety, palpitations, and tremor. These agents may be used in conjunction with antithyroid medications or radioactive iodine for symptomatic relief only.

Answer d is incorrect. Ibuprofen will not provide symptomatic relief for the typical symptoms of hyperthyroidism.

You are consulted by Dr. X to determine the plan for a patient's methimazole dose. She has been taking methimazole for 2 months. What ...

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