What is the initial treatment for hyperthyroidism?

Initial Treatment for Hyperthyroidism

The initial treatment for hyperthyroidism is antithyroid medication, specifically methimazole, which inhibits thyroid hormone synthesis and is the preferred first-line pharmacological therapy for most patients with hyperthyroidism. 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 accounts for 70% of cases, toxic nodular goiter for 16%, thyroiditis for 3%, and drug-induced for 9%) 2

Treatment Algorithm

First-Line Treatment:

1. Methimazole (Thionamide)

   • Initial dose: 0.5-1.5 μg/kg/day 3
   • Can be administered as a single daily dose 4
   • Preferred over propylthiouracil, especially in pediatric patients due to lower risk of severe liver injury 1
   • Monitor thyroid function tests every 4-6 weeks until stable, then annually 3

2. Beta-blockers (for symptomatic patients)

   • Add propranolol or atenolol/metoprolol for symptom control (palpitations, tremor, anxiety) 5
   • Can be continued until patient becomes asymptomatic 5

Treatment Based on Severity:

For Mild to Moderate Hyperthyroidism (Grade 1-2):

• Continue immunotherapy if applicable
• Start beta-blockers if symptomatic
• Initiate methimazole
• Resume immunotherapy when asymptomatic 5

For Severe Hyperthyroidism (Grade 3-4):

• Interrupt immunotherapy if applicable
• Hospitalize if necessary
• Start high-dose methimazole
• Consider consulting endocrinology 5

Monitoring and Dose Adjustment

• Check TSH and free T4 every 4-6 weeks until stable 3
• Adjust methimazole dose in 12.5-25 mcg increments until TSH normalizes 3
• Monitor prothrombin time before surgical procedures due to potential bleeding risk 1
• Target TSH within normal range (0.45-4.5 mIU/L) for primary hyperthyroidism 3

Important Considerations

Drug Interactions

• Methimazole may increase activity of oral anticoagulants (warfarin) 1
• Hyperthyroid patients becoming euthyroid may require dose reductions of:
  • Beta-blockers
  • Digitalis glycosides
  • Theophylline 1

Special Populations

1. Pregnant Women:

   • Methimazole is pregnancy category D
   • Consider propylthiouracil in first trimester due to lower risk of congenital malformations
   • Switch to methimazole in second and third trimesters due to lower risk of hepatotoxicity 1
   • Monitor closely and adjust dose as pregnancy progresses 1

2. Nursing Mothers:

   • Methimazole is present in breast milk but generally considered safe
   • Monitor infant's thyroid function regularly 1

3. Elderly Patients:

   • More likely to progress to overt hyperthyroidism
   • Require more aggressive monitoring and management 3

Potential Adverse Effects

• Agranulocytosis (rare but serious)
• Vasculitis
• Skin eruptions
• Hypoprothrombinemia 1

Long-term Management

• Treatment duration typically 12-18 months, with 50% recurrence rate 2, 6
• Long-term treatment (5-10 years) associated with fewer recurrences (15%) 2
• If hyperthyroidism recurs after antithyroid medication, consider definitive therapy with radioactive iodine ablation or thyroidectomy 7, 8

Caution

Patients should immediately report symptoms such as sore throat, skin eruptions, fever, headache, or general malaise, which could indicate agranulocytosis. White blood cell and differential counts should be obtained in such cases 1.