Initial Treatment for Hyperthyroidism
The initial treatment for hyperthyroidism should be a beta-blocker to control symptoms, followed by methimazole as the antithyroid medication of choice for most patients. 1, 2, 3
First-Line Treatment Approach
Step 1: Beta-Blockers for Symptom Control
- Beta-blockers (e.g., propranolol 60-80 mg orally every 4-6 hours) should be started immediately to manage cardiac-related symptoms 1, 2
- Benefits include:
- Rapid improvement in tachycardia and other cardiovascular symptoms
- Does not affect thyroid hormone levels but controls manifestations
- Particularly important in patients with atrial fibrillation or other arrhythmias
Step 2: Antithyroid Medication
Methimazole (MMI) is the preferred antithyroid drug for most patients 2, 3, 4
- More effective than propylthiouracil (PTU) in single daily dosing
- Longer half-life allowing once-daily dosing
- Fewer severe side effects
- Starting dose typically 15 mg daily 4
Propylthiouracil (PTU) should be reserved for specific situations 5:
- Patients who cannot tolerate methimazole
- During or just prior to first trimester of pregnancy
- Thyroid storm (as PTU also inhibits peripheral conversion of T4 to T3)
Treatment Selection Based on Etiology
For Graves' Disease (most common cause):
- Antithyroid medications (methimazole preferred)
- Radioactive iodine ablation (most widely used in the US)
- Surgical thyroidectomy
For Toxic Multinodular Goiter or Toxic Adenoma:
- Same treatment options as Graves' disease
- Choice depends on patient factors and preferences
For Thyroiditis (painless/silent):
- Primarily supportive care and beta-blockers
- Self-limiting condition that typically resolves without antithyroid drugs
Monitoring and Adjustments
- Check thyroid function (TSH, Free T4) 4-6 weeks after starting therapy 2
- Adjust dose based on response
- Monitor for side effects of methimazole:
- Agranulocytosis (presents with sore throat and fever)
- Hepatitis
- Vasculitis
- Thrombocytopenia 2
Special Considerations
Subclinical Hyperthyroidism
- For TSH 0.1-0.45 mIU/L: Generally not treated routinely 1
- For TSH <0.1 mIU/L: Consider treatment in patients >65 years or with cardiac disease 6
Thyroid Storm (Life-Threatening Emergency)
- Requires immediate hospitalization
- Treatment includes:
- PTU or methimazole
- Potassium iodide solution
- Dexamethasone
- Beta-blockers
- Supportive care 2
Pregnancy Considerations
- PTU preferred in first trimester
- Can switch to methimazole after first trimester
- Close monitoring required 5
Cautions and Pitfalls
- Never start antithyroid medication without checking for adrenal insufficiency in patients with suspected multiple endocrine deficiencies
- PTU carries FDA warning for severe liver injury and acute liver failure 5
- Overtreatment with antithyroid drugs can lead to hypothyroidism
- Beta-blockers may be contraindicated in some patients with severe asthma or heart failure; calcium channel blockers (diltiazem, verapamil) can be alternatives 2
The evidence clearly supports initiating treatment with a beta-blocker for symptom control while simultaneously starting methimazole as the antithyroid drug of choice for most patients with hyperthyroidism, with specific exceptions as noted above.