What are the treatment options for hyperthyroidism?

Treatment for Hyperthyroidism

For most patients with hyperthyroidism, methimazole is the preferred first-line antithyroid drug due to its superior efficacy, safety profile, and once-daily dosing convenience, with the critical exception of first-trimester pregnancy when propylthiouracil must be used. 1, 2

Immediate Symptomatic Management

Beta-blockers should be initiated immediately for symptomatic relief while awaiting thyroid hormone normalization:

• Atenolol 25-50 mg daily or propranolol are the preferred agents for controlling tachycardia, tremor, and anxiety symptoms 1, 2
• Beta-blockers are particularly critical for patients with cardiac symptoms, as hyperthyroidism increases cardiac output by up to 300% and causes atrial fibrillation in 5-15% of patients (more frequently in those over 60 years) 3, 2
• Dose reduction is required once the patient achieves euthyroid state to avoid excessive bradycardia 2, 4

Definitive Treatment Options

Antithyroid Drug Therapy

Methimazole (First-Line):

• Starting dose: 10-30 mg once daily 5, 6
• Preferred due to superior efficacy, longer half-life, fewer severe side effects, and lower cost 1, 6
• Monitor free T4 or free T3 every 2-4 weeks initially, then every 4-6 weeks once stable 1, 2
• Treatment duration typically 12-18 months for Graves' disease with goal of inducing remission 7
• Methimazole is 4 times more effective at inducing euthyroidism compared to propylthiouracil at equivalent doses 8, 9

Propylthiouracil (Reserved for Specific Situations):

• Only use for: patients intolerant to methimazole, first trimester of pregnancy, or when surgery/radioiodine are inappropriate 4
• Starting dose: 100-300 mg every 6-8 hours (requires multiple daily doses) 5
• Critical warning: Propylthiouracil carries risk of severe hepatotoxicity, including hepatic failure requiring transplantation or resulting in death, particularly in pregnant women and pediatric patients 4

Radioactive Iodine (I-131) Therapy

• Growing use as first-line definitive therapy for most patients with Graves' disease or toxic nodular goiter 7
• Absolutely contraindicated in pregnancy and breastfeeding; pregnancy must be avoided for 4 months following administration 2, 7
• Well-tolerated with primary long-term consequence being hypothyroidism requiring lifelong thyroid hormone replacement 1, 7
• May worsen Graves' ophthalmopathy; consider corticosteroid prophylaxis in patients with active eye disease 2, 7

Surgical Thyroidectomy

Indications for near-total or total thyroidectomy:

• Large goiters causing compressive symptoms 1, 7
• Suspicious thyroid nodules requiring pathologic evaluation 1
• Severe ophthalmopathy 1
• Patient refusal of radioiodine therapy 7
• Requires lifelong thyroid hormone replacement post-operatively 1

Critical Monitoring for Life-Threatening Adverse Effects

Agranulocytosis (typically occurs within first 3 months):

• Immediately discontinue antithyroid drug and obtain CBC if patient develops: sore throat, fever, or signs of infection 2, 4
• This is a medical emergency requiring immediate evaluation 1

Hepatotoxicity (especially with propylthiouracil):

• Stop drug immediately if patient develops: fever, nausea, vomiting, right upper quadrant pain, dark urine, jaundice, or light-colored stools 2, 4
• Monitor liver function tests, particularly in first 6 months 4

Vasculitis (can be life-threatening):

• Discontinue drug if patient develops: new rash, hematuria, decreased urine output, dyspnea, or hemoptysis 2, 4

Special Clinical Scenarios

Pregnancy Management

• First trimester: Propylthiouracil is preferred despite hepatotoxicity risk, as methimazole is associated with rare fetal abnormalities (aplasia cutis, choanal/esophageal atresia) 1, 5
• Second and third trimesters: Consider switching to methimazole to reduce maternal hepatotoxicity risk 1
• Goal: Maintain free T4 in high-normal range using lowest possible dose 1, 2
• Monitor every 2-4 weeks during pregnancy 1, 2
• Both drugs are safe during breastfeeding 1, 4

Thyroiditis-Induced Hyperthyroidism

• Self-limited condition requiring only symptomatic management with beta-blockers 1, 2
• Antithyroid drugs are NOT indicated as this is destructive thyroiditis, not increased hormone synthesis 1, 2
• Most patients transition to primary hypothyroidism requiring close monitoring and eventual thyroid hormone replacement 1

Severe Hyperthyroidism/Thyroid Storm

• Mandatory hospitalization and endocrine consultation 1
• Aggressive management with high-dose beta-blockers, high-dose antithyroid drugs, hydration, and supportive care 1
• Consider additional therapies: corticosteroids, saturated solution of potassium iodide (SSKI), or emergency surgery 1

Subclinical Hyperthyroidism

• Consider treatment for TSH <0.1 mIU/L, particularly in patients over 60 years or those with increased cardiovascular risk, osteopenia, or osteoporosis 2
• TSH <0.1 mIU/L carries 3-fold increased risk of atrial fibrillation over 10 years in patients over 60 2
• Routine treatment NOT recommended for TSH 0.1-0.45 mIU/L due to insufficient evidence of adverse outcomes 2

Important Drug Interactions Requiring Dose Adjustments

• Warfarin: Increased anticoagulation effect when taking antithyroid drugs; requires additional PT/INR monitoring 2, 4
• Digoxin: Serum levels increase as patient becomes euthyroid; may require dose reduction 2, 4
• Theophylline: Clearance decreases when euthyroid; may require dose reduction 2, 4
• Beta-blockers: Hyperthyroidism increases clearance; dose reduction needed once euthyroid 2, 4

Common Pitfalls to Avoid

• Never use propylthiouracil as first-line therapy except in first trimester pregnancy or methimazole intolerance, given severe hepatotoxicity risk 4, 6
• Do not use antithyroid drugs for thyroiditis-induced hyperthyroidism—this wastes time and exposes patients to unnecessary drug risks 1, 2
• Do not forget to reduce beta-blocker doses once euthyroid state is achieved to prevent symptomatic bradycardia 2, 4
• Toxic nodular goiter will not achieve remission with antithyroid drugs alone—definitive therapy (radioiodine or surgery) is required 7