Initial Treatment for Hyperthyroidism
Beta-blockers should be started immediately for symptomatic relief while simultaneously initiating antithyroid drug therapy with methimazole as the preferred agent, monitoring thyroid function every 2-3 weeks. 1, 2
Immediate Symptomatic Management
- Beta-blockers (atenolol or propranolol) are the first-line symptomatic treatment for managing cardiac symptoms including tachycardia, tremor, and anxiety while waiting for antithyroid medications to take effect 1, 2
- Continue beta-blocker therapy until thioamide therapy reduces thyroid hormone levels to the therapeutic range 1
- Beta-blockers are particularly critical for patients presenting with cardiac symptoms and should not be delayed 1
Antithyroid Drug Selection
Methimazole is the preferred first-line antithyroid drug for most patients with the following critical exceptions 1, 3, 4:
When to Use Methimazole (Preferred)
- All non-pregnant patients without contraindications 4, 5
- Starting dose should not exceed 15-20 mg/day to minimize risk of dose-dependent agranulocytosis 4
- Safer hepatic profile compared to propylthiouracil 3, 4
When Propylthiouracil is Indicated (Limited Use)
- During or just prior to the first trimester of pregnancy only 1, 3
- Patients who cannot tolerate methimazole 3
- Critical warning: Propylthiouracil carries a black box warning for severe liver injury, acute liver failure, and death 3
- Propylthiouracil should NOT be used as a first-line agent due to risk of fatal hepatotoxicity requiring liver transplantation 3, 4
Monitoring Protocol
- Monitor thyroid function tests every 2-3 weeks initially after starting antithyroid drugs 1, 2
- Once stable, extend monitoring to every 4-6 weeks with dose adjustments based on clinical response 1
- Watch for transition to hypothyroidism, which commonly occurs after treatment 2
Treatment Duration and Definitive Therapy Planning
- Antithyroid drugs are typically continued for 12-18 months to induce remission in Graves disease 6, 5
- If TSH receptor antibodies remain above 10 mU/L after 6 months of treatment, remission is unlikely and definitive therapy (radioactive iodine or thyroidectomy) should be recommended 4
- For toxic nodular goiter, antithyroid drugs will not cure the condition—definitive therapy with radioactive iodine is the treatment of choice 6, 5
Critical Safety Monitoring
Patients must be counseled to stop antithyroid drugs immediately and contact their physician if they develop: 1, 2
- Fever, chills, or sore throat (agranulocytosis—most common in first 3 months) 2, 3
- Jaundice, dark urine, pale stools, right upper quadrant pain (hepatotoxicity) 1, 3
- Skin rash, joint pain, or vasculitis symptoms 3
Special Clinical Scenarios
Thyroiditis-Induced Hyperthyroidism
- Do NOT use antithyroid drugs as this is self-limited 1
- Treat with beta-blockers for symptom management only 1
- Monitor closely for transition to hypothyroidism requiring thyroid hormone replacement 1, 2
Severe Hyperthyroidism/Thyroid Storm
- Requires immediate hospitalization 1, 2
- Aggressive management with beta-blockers, high-dose antithyroid drugs, hydration, and supportive care 1
- Consider additional therapies including steroids and SSKI 1
- Mandatory endocrinology consultation 1, 2
Pregnancy Considerations
- Propylthiouracil is preferred during first trimester only 1, 3
- Goal is maintaining FT4 in high-normal range using lowest possible thioamide dosage 1
- Monitor FT4 every 2-4 weeks during pregnancy 1
- Women treated with either propylthiouracil or methimazole can breastfeed safely 1
Common Pitfalls to Avoid
- Never delay beta-blocker initiation while waiting for antithyroid drug effects, which take weeks 1
- Never use propylthiouracil as first-line therapy except in first trimester pregnancy due to fatal hepatotoxicity risk 3, 4
- Never prescribe antithyroid drugs for thyroiditis—this is a self-limited condition requiring only symptomatic management 1
- Never start methimazole at doses exceeding 20 mg/day due to increased agranulocytosis risk 4