What is the initial treatment for hyperthyroidism?

Initial Treatment for Hyperthyroidism

The initial treatment for hyperthyroidism is antithyroid medication, specifically methimazole (MMI), which is the drug of choice for most patients due to its longer half-life, once-daily dosing, and fewer severe side effects compared to propylthiouracil (PTU). 1, 2

Diagnosis Confirmation

Before initiating treatment, confirm hyperthyroidism with:

• Low TSH and elevated free T4 and/or free T3 levels
• Determine etiology (most commonly Graves' disease [70%] or toxic nodular goiter [16%]) 3
• Consider thyroid antibody testing, ultrasonography, or scintigraphy to establish the specific cause

First-Line Medication Treatment

Methimazole (MMI)

• Preferred first-line agent for most patients
• Starting dose: 15-30mg daily (can be given as single daily dose)
• More effective than PTU in achieving euthyroidism (77.1% vs 19.4% at 12 weeks) 4
• Advantages: longer half-life, once-daily dosing, fewer severe side effects

Propylthiouracil (PTU)

• Reserved for specific situations:
  • First trimester of pregnancy or planning pregnancy
  • Patients who cannot tolerate methimazole
  • Thyroid storm (as it also blocks peripheral T4 to T3 conversion)
• Starting dose: 100-150mg three times daily
• FDA Warning: Severe liver injury and acute liver failure risk, some cases fatal 5

Beta-Blockers for Symptom Control

• Add beta-blockers (propranolol or atenolol/metoprolol) for symptomatic patients
• Helps control tachycardia, palpitations, tremor, anxiety, and heat intolerance
• Can be discontinued once patient becomes euthyroid 6

Treatment Based on Severity

For Mild Symptomatic Hyperthyroidism

• Start methimazole 15mg daily
• Add beta-blocker if symptomatic
• Recheck thyroid function in 4-6 weeks

For Moderate to Severe Hyperthyroidism

• Start methimazole 20-30mg daily
• Add beta-blocker for symptom control
• Consider more frequent monitoring (2-4 weeks initially)

Monitoring and Follow-up

• Check thyroid function tests (TSH, free T4, free T3) every 4-6 weeks initially
• Once stable, monitor every 3-6 months
• Watch for side effects: rash, pruritus, arthralgias, fever, abnormal liver function tests, or agranulocytosis
• Instruct patients to report sore throat, fever, or rash immediately

Treatment Duration and Alternatives

For Graves' disease:

• Standard course: 12-18 months of antithyroid drugs
• Recurrence rate: approximately 50% after standard course
• Long-term treatment (5-10 years) associated with fewer recurrences (15%) 3

Alternative definitive treatments:

• Radioactive iodine ablation (most widely used in the US)
• Surgical thyroidectomy

Special Considerations

Subclinical Hyperthyroidism

• TSH 0.1-0.45 mIU/L: Generally monitor without treatment
• TSH <0.1 mIU/L: Consider treatment in patients >65 years or with cardiac disease/osteoporosis risk 6, 7

Pregnancy

• PTU preferred in first trimester
• Switch to MMI after first trimester
• Close monitoring required 5

Thyroid Storm

• Medical emergency requiring hospitalization
• PTU may be preferred due to its additional effect of blocking peripheral conversion of T4 to T3 5

Remember that the choice between continued antithyroid medication, radioactive iodine, or surgery should be made after the initial control of hyperthyroidism is achieved, considering factors such as the underlying cause, patient preference, and contraindications to specific treatments.