What is the initial treatment for hyperthyroidism?

Initial Treatment for Hyperthyroidism

For most patients with hyperthyroidism, begin with beta-blocker therapy (atenolol 25-50 mg daily or propranolol) for immediate symptom control, followed by antithyroid medication with methimazole as the preferred first-line agent at 10-30 mg daily as a single dose. 1

Immediate Symptomatic Management

• Start a beta-blocker immediately for symptomatic relief of tachycardia, tremor, anxiety, and heat intolerance while awaiting definitive thyroid hormone reduction 1
• Atenolol 25-50 mg daily or propranolol are the preferred agents, titrating to maintain heart rate <90 bpm if blood pressure tolerates 1
• Beta-blockers provide rapid symptom control within hours to days, while antithyroid drugs require weeks to normalize thyroid hormone levels 1

Definitive Antithyroid Drug Therapy

First-Line Agent: Methimazole

• Methimazole is the preferred initial antithyroid drug for nearly all patients with hyperthyroidism due to lower rates of major side effects, once-daily dosing, lower cost, and better availability 2, 3
• Starting dose: 10-30 mg once daily (do not exceed 15-20 mg/day to minimize agranulocytosis risk) 2, 3
• Monitor free T4 or free thyroxine index every 2-4 weeks initially, adjusting dose to maintain thyroid hormones in the high-normal range 1

When to Use Propylthiouracil Instead

Propylthiouracil should be reserved for specific situations only due to risk of severe liver failure, liver transplantation, and death 4:

• First trimester of pregnancy or immediately prior to conception (methimazole is associated with aplasia cutis and choanal/esophageal atresia) 1, 4, 3
• Patients who have experienced adverse reactions to methimazole 4, 2
• Thyroid storm (PTU inhibits peripheral T4 to T3 conversion) 4

When PTU is used, the starting dose is 100-300 mg every 6-8 hours (requires three-times-daily dosing) 1, 3

Critical Safety Monitoring

Agranulocytosis Warning

• Instruct all patients to stop antithyroid drugs immediately and obtain complete blood count if they develop fever, sore throat, or signs of infection 1, 4
• Agranulocytosis typically occurs within the first 3 months of therapy and is dose-dependent 4, 2

Liver Toxicity Warning (Propylthiouracil)

• Stop PTU immediately if patients develop fever, loss of appetite, nausea, vomiting, right upper quadrant pain, dark urine, pale stools, or jaundice 4
• PTU can cause fatal acute liver failure requiring transplantation 4, 2

Special Populations

Pregnancy

• Use propylthiouracil in the first trimester, then consider switching to methimazole in the second trimester 1, 4
• Goal: maintain free T4 in the high-normal range using the lowest possible dose 1
• Both drugs are compatible with breastfeeding 1, 3

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

• Hospitalize the patient 1
• Beta-blocker therapy 1
• Hydration and supportive care 1
• Endocrine consultation for consideration of additional therapies including steroids, saturated solution of potassium iodide (SSKI), or thionamides 1
• Consider surgery for refractory cases 1

Treatment Duration and Monitoring

• Continue antithyroid drug therapy for 12-24 months for Graves disease 2, 5
• If TSH receptor antibodies remain >10 mU/L after 6 months of treatment, remission is unlikely—consider definitive therapy with radioactive iodine or thyroidectomy 2
• Monitor thyroid function every 2-3 weeks initially, then every 2-4 months once stable 1

Common Pitfalls to Avoid

• Do not use propylthiouracil as first-line therapy except in the specific situations noted above due to hepatotoxicity risk 4, 2
• Do not exceed methimazole starting doses of 15-20 mg/day to minimize agranulocytosis risk 2
• Do not use radioactive iodine in pregnant women—it is absolutely contraindicated 1
• Do not forget to educate patients about agranulocytosis warning signs before starting any thionamide 1, 4