What is the initial treatment for hyperthyroidism?

Initial Treatment for Hyperthyroidism

The initial treatment for hyperthyroidism is methimazole (antithyroid medication), with beta-blockers added for symptomatic patients. 1, 2

Diagnosis Confirmation

Before initiating treatment, confirm hyperthyroidism with:

• Low TSH and elevated free T4 and/or free T3 levels
• Determine etiology (Graves' disease, toxic nodular goiter, thyroiditis)
• Consider TSH-receptor antibodies, thyroid peroxidase antibodies, ultrasound, or scintigraphy if etiology is unclear 3

Treatment Algorithm

First-Line Therapy

1. Antithyroid Medication (Methimazole)

   • Initial dosing:
     • Mild to moderate hyperthyroidism: 20 mg daily 4
     • Severe hyperthyroidism or large goiter: 30-40 mg daily 4
   • Can be administered as a single daily dose 5
   • Monitor thyroid function tests every 4-6 weeks initially

2. Symptomatic Management with Beta-Blockers

   • For patients with symptoms (tachycardia, tremor, anxiety)
   • Options include propranolol or atenolol/metoprolol 2
   • Continue until symptoms resolve

Special Considerations

• Pregnancy:

  • Propylthiouracil is preferred in first trimester due to lower risk of birth defects
  • Switch to methimazole for second and third trimesters 1
  • Use lowest effective dose

• Breastfeeding:

  • Methimazole is compatible with breastfeeding 1
  • Monitor infant's thyroid function

• Children:

  • Methimazole is preferred over propylthiouracil due to lower risk of severe liver injury 1

Monitoring and Follow-up

• Check thyroid function tests (TSH, free T4, free T3) every 4-6 weeks until stable
• Monitor for side effects:
  • Agranulocytosis (sore throat, fever, infection)
  • Hepatotoxicity
  • Skin rashes
  • Vasculitis
• Adjust dose based on clinical response and lab values
• Maintenance dose typically 5-10 mg daily 4

Treatment Duration and Alternatives

• Standard course: 12-18 months of antithyroid drugs 4
• Recurrence rate after discontinuation: approximately 50% 3
• Alternative treatments if antithyroid drugs fail or are contraindicated:
  1. Radioactive iodine ablation (most common definitive treatment in the US) 6
  2. Surgical thyroidectomy 6

Important Caveats

• Patients should be educated about potential side effects and instructed to report immediately any signs of infection, rash, jaundice, or unusual bleeding
• Methimazole may interact with anticoagulants, beta-blockers, digitalis, and theophylline; dose adjustments may be needed 1
• For thyroiditis-induced hyperthyroidism, which is self-limiting, supportive care with beta-blockers may be sufficient without antithyroid drugs 2

By following this treatment approach, most patients will achieve euthyroidism within 14-17 weeks 5, significantly reducing the risk of complications such as cardiac arrhythmias, heart failure, osteoporosis, and adverse pregnancy outcomes 7.