What medications are used to treat hyperthyroidism?

Medications for Hyperthyroidism

Beta-blockers (atenolol or propranolol) are the first-line symptomatic treatment for all grades of hyperthyroidism, while thionamides (methimazole or propylthiouracil) are the definitive antithyroid medications used for persistent or severe cases. 1

Symptomatic Management: Beta-Blockers

All patients with hyperthyroidism should receive beta-blockers for symptomatic relief, regardless of severity 1:

• Atenolol or propranolol are specifically recommended to control tachycardia, tremor, heat intolerance, and other adrenergic symptoms 1
• Beta-blockers are particularly critical in thyroid storm and when elevated catecholamine states are present 1
• For patients with atrial fibrillation secondary to hyperthyroidism, beta-blockers are the preferred rate control agents 1
• Nondihydropyridine calcium channel antagonists (diltiazem or verapamil) are the alternative when beta-blockers cannot be used 1

Definitive Antithyroid Medications: Thionamides

Methimazole (Preferred Agent)

Methimazole is the preferred thionamide in most clinical situations 2, 3, 4, 5:

• Inhibits thyroid hormone synthesis by blocking thyroid peroxidase enzyme 3
• More effective than propylthiouracil with fewer adverse effects 5
• Once-daily dosing due to longer half-life improves adherence 5
• Used for 12-18 months to induce remission in Graves' disease 6, 7
• Avoid in first trimester of pregnancy due to rare teratogenic effects (aplasia cutis, choanal atresia) 2, 5

Propylthiouracil (PTU)

Propylthiouracil is reserved for specific situations 2, 4, 5:

• First trimester of pregnancy (weeks 0-16) when methimazole is contraindicated 2, 5
• Thyroid storm, as PTU additionally blocks peripheral conversion of T4 to T3 2
• Patients with methimazole allergy or intolerance 4
• Higher risk of severe hepatotoxicity compared to methimazole, particularly in first 6 months 2
• Requires multiple daily doses due to shorter half-life 5

Severe/Life-Threatening Hyperthyroidism (Grade 3-4)

For patients with severe symptoms or thyroid storm, combination therapy is required 1:

• Beta-blockers (atenolol or propranolol) for immediate symptom control 1
• Thionamides (methimazole or propylthiouracil) to block hormone synthesis 1
• Corticosteroids to reduce T4-to-T3 conversion and treat inflammatory component 1
• SSKI (saturated solution of potassium iodide) to block thyroid hormone release 1
• Hospitalization with endocrine consultation is mandatory 1

Treatment Algorithm by Severity

Mild Symptoms (Grade 1)

• Beta-blocker monotherapy for symptomatic relief 1
• Monitor thyroid function every 2-3 weeks 1
• Add thionamide if thyrotoxicosis persists beyond 6 weeks 1

Moderate Symptoms (Grade 2)

• Beta-blocker plus hydration/supportive care 1
• Consider endocrine consultation 1
• Add thionamide if persistent beyond 6 weeks 1

Severe Symptoms (Grade 3-4)

• Full combination therapy as outlined above 1
• Mandatory endocrine consultation and possible hospitalization 1
• Consider surgery if medical therapy fails 1

Critical Monitoring Requirements

For propylthiouracil specifically 2:

• Monitor liver function (bilirubin, alkaline phosphatase, ALT/AST) especially in first 6 months 2
• Obtain CBC with differential if fever, sore throat, or malaise develops (agranulocytosis risk) 2
• Monitor PT/INR if on anticoagulants, as PTU potentiates warfarin 2
• Report immediately: jaundice, dark urine, right upper quadrant pain, new rash, hematuria 2

For all antithyroid drugs 4, 5, 7:

• Check TSH and free T4 every 4-6 weeks during titration 4
• Monitor for agranulocytosis (0.2-0.5% incidence) - obtain CBC if infection symptoms 5
• Watch for hepatotoxicity, particularly with PTU 2, 5

Common Pitfalls to Avoid

• Never use methimazole in first trimester of pregnancy - switch to PTU 2, 5
• Do not use beta-blockers alone for definitive treatment - they only provide symptomatic relief 1
• Avoid radioactive iodine in Graves' ophthalmopathy - may worsen eye disease 6, 8
• Do not delay corticosteroids in thyroid storm - critical for blocking T4-to-T3 conversion 1
• Failing to monitor for agranulocytosis can be fatal - educate patients to report fever/sore throat immediately 2, 5