What is the initial treatment for hyperthyroidism?

Initial Treatment for Hyperthyroidism

The initial treatment for hyperthyroidism should be antithyroid medications, with methimazole as the first-line agent for most patients, except during the first trimester of pregnancy when propylthiouracil is preferred. 1, 2, 3, 4

Diagnostic Confirmation

Before initiating treatment, confirm the diagnosis with:

• TSH (suppressed)
• Free T4 and/or Free T3 (elevated)
• Determine etiology (Graves' disease, toxic nodular goiter, thyroiditis)
  • TSH-receptor antibodies
  • Thyroid peroxidase antibodies
  • Thyroid ultrasonography
  • Thyroid scintigraphy (especially if nodules are present) 3, 4

Treatment Algorithm

First-Line Treatment: Antithyroid Medications

1. Methimazole (MMI):

   • Preferred first-line agent due to:
     • Once-daily dosing
     • Greater efficacy in normalizing thyroid hormones
     • Lower hepatotoxicity compared to PTU 5, 6
   • Initial dosing:
     • Mild to moderate hyperthyroidism: 15 mg once daily
     • Severe hyperthyroidism (FT4 ≥7 ng/dl): 30 mg once daily 6

2. Propylthiouracil (PTU):

   • Reserved for specific situations:
     • First trimester of pregnancy
     • Patients who cannot tolerate methimazole
     • Thyroid storm (due to additional inhibition of T4 to T3 conversion) 2
   • Initial dosing: 100-150 mg three times daily (total 300-450 mg/day) 2
   • Warning: PTU carries FDA black box warning for severe liver injury 2

Alternative Treatments

For patients who fail medical therapy, have contraindications, or prefer definitive treatment:

1. Radioactive Iodine (RAI) Ablation:

   • Most widely used treatment in the United States
   • Particularly effective for toxic nodular goiter
   • Contraindicated in pregnancy and breastfeeding 7, 4

2. Surgical Thyroidectomy:

   • Indicated for:
     • Large goiters causing compressive symptoms
     • Suspected/confirmed thyroid malignancy
     • Patients desiring rapid and definitive treatment
     • Pregnant women who cannot tolerate antithyroid drugs 7, 4

Monitoring and Follow-up

• Recheck thyroid function tests (TSH, free T4, free T3) at 4,8, and 12 weeks after initiating treatment
• Monitor for adverse effects:
  • Methimazole: rash, arthralgia, agranulocytosis (rare)
  • Propylthiouracil: hepatotoxicity, agranulocytosis, vasculitis 2
• Adjust medication dose based on thyroid function tests
• Typical duration of antithyroid drug treatment: 12-18 months (with 50% risk of recurrence) 3
• Consider long-term treatment (5-10 years) for lower recurrence rate (15%) 3

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
  • Those with cardiac disease or osteoporosis
  • Postmenopausal women 8, 1

Thyroid Storm (Medical Emergency)

Requires immediate treatment with:

1. PTU (preferred due to inhibition of T4 to T3 conversion)
2. Beta-blockers (propranolol 60-80 mg every 4-6 hours)
3. Corticosteroids (dexamethasone)
4. Saturated solution of potassium iodide
5. Supportive care 1, 2

Pitfalls to Avoid

• Never start thyroid hormone replacement in patients with central hypothyroidism without first ensuring adequate cortisol replacement (can precipitate adrenal crisis) 1
• Do not rely on a single abnormal laboratory value for major treatment decisions; confirm with repeat testing 1
• Avoid overtreatment with antithyroid drugs, which can lead to hypothyroidism 1
• Monitor for rare but serious side effects of antithyroid drugs (agranulocytosis, hepatotoxicity) 2

The choice between treatment modalities should consider the underlying cause of hyperthyroidism, disease severity, patient age, comorbidities (especially cardiac disease), and pregnancy status.