What is the recommended treatment for thyrotoxicosis?

Treatment of Thyrotoxicosis

Beta-blockers (propranolol or atenolol) are the first-line treatment for symptomatic control in all patients with thyrotoxicosis, followed by definitive therapy with antithyroid drugs (methimazole preferred over propylthiouracil), radioactive iodine, or surgery depending on the underlying etiology. 1, 2

Immediate Symptomatic Management

All symptomatic patients require beta-blocker therapy unless contraindicated:

• Propranolol or atenolol should be initiated immediately to control tachycardia, tremor, and hyperadrenergic symptoms 1, 2
• For atrial fibrillation complicating thyrotoxicosis, beta-blockers are Class I recommended (highest level) 1
• In thyroid storm, aggressive intravenous beta-blocker therapy is critical and may require high doses 1

When beta-blockers are contraindicated:

• Use non-dihydropyridine calcium channel antagonists (diltiazem or verapamil) as Class I alternatives 1, 2

Definitive Treatment Based on Etiology

For Graves' Disease (Most Common Cause)

Methimazole is the preferred antithyroid drug:

• Start methimazole 15-20 mg/day maximum as initial dose to minimize agranulocytosis risk 3, 4
• Propylthiouracil should NOT be used as first-line therapy due to severe hepatotoxicity risk causing liver failure, transplantation, or death 5, 4
• Propylthiouracil is only indicated when methimazole is not tolerated or during first trimester pregnancy 5, 3, 4

Duration and monitoring of antithyroid drug therapy:

• Continue methimazole for 12-18 months, then reassess for remission 6, 7
• If TSH-receptor antibodies remain >10 mU/L after 6 months of treatment, remission is unlikely and definitive therapy (radioiodine or surgery) should be recommended 4
• For patients >35 years, long-term low-dose methimazole (2.5-5 mg/day) may prevent relapse better than drug discontinuation 8

Definitive therapy options:

• Radioactive iodine therapy: Stop methimazole at least one week prior to treatment to reduce failure risk 4
• Total or near-total thyroidectomy: Preferred surgical approach when surgery is chosen 4

For Toxic Adenoma or Toxic Multinodular Goiter

• Radioactive iodine is the definitive treatment of choice 4
• Stop antithyroid drugs at least one week before radioiodine administration 4
• Surgery (total thyroidectomy) is an alternative when radioiodine is contraindicated 4

For Thyroiditis-Related Thyrotoxicosis

Conservative management is sufficient:

• Beta-blockers for symptomatic control are the mainstay 2
• The thyrotoxic phase is self-limiting, resolving in approximately 1 month 2
• Do NOT use antithyroid drugs as this is destructive thyroiditis, not increased hormone synthesis 2
• Monitor thyroid function every 2-3 weeks as most patients transition to hypothyroidism requiring levothyroxine 2

Thyroid Storm Management

Thyroid storm requires aggressive multi-drug therapy:

• High-dose intravenous beta-blockers (propranolol) 9
• Thionamides (methimazole or propylthiouracil) to block new hormone synthesis 9
• Iodine (given 1 hour AFTER thionamides) to inhibit hormone release 9
• Corticosteroids (dexamethasone or hydrocortisone) to block peripheral T4 to T3 conversion 9
• Supportive therapy including cooling, hydration, and treatment of precipitating factors 9

Alternative agents when standard therapy fails:

• Cholestyramine to interrupt enterohepatic circulation 9
• Lithium carbonate as iodine substitute 9
• Potassium perchlorate in specific circumstances 9

Anticoagulation for Atrial Fibrillation

Oral anticoagulation (INR 2.0-3.0) is Class I recommended:

• All patients with thyrotoxicosis-induced atrial fibrillation require anticoagulation to prevent thromboembolism 1
• Continue anticoagulation until euthyroid state is restored and atrial fibrillation resolves 1
• Once euthyroid, follow standard stroke risk stratification for continued anticoagulation decisions 1

Critical Pitfalls to Avoid

Do not use propylthiouracil as first-line therapy:

• Severe hepatotoxicity can cause liver failure requiring transplantation or death 5, 4
• Reserve only for methimazole intolerance or first trimester pregnancy 5, 3

Do not give iodine before thionamides in thyroid storm:

• Iodine must be given at least 1 hour AFTER thionamides to prevent worsening thyrotoxicosis 9

Do not use antithyroid drugs for thyroiditis:

• Destructive thyroiditis is self-limiting and does not involve increased hormone synthesis 2
• Beta-blockers alone provide adequate symptomatic control 2

Do not use digoxin, diltiazem, or verapamil in WPW syndrome with atrial fibrillation:

• These agents are Class III contraindicated as they can accelerate ventricular response through accessory pathway 1

Do not start thyroid hormone before corticosteroids when both adrenal insufficiency and hypothyroidism coexist:

• This precipitates adrenal crisis 2

Special Populations

Pregnancy:

• Propylthiouracil is preferred during first trimester due to methimazole teratogenicity risk 3, 7
• Switch to methimazole for second and third trimesters to avoid propylthiouracil hepatotoxicity 3, 7
• Use lowest effective antithyroid drug dose to maintain maternal free T4 at upper normal range 7

Children and adolescents:

• Methimazole is strongly preferred over propylthiouracil due to severe pediatric hepatotoxicity reports 3

Elderly patients:

• Beta-blockers require careful dosing due to increased cardiac sensitivity 1
• Consider earlier definitive therapy (radioiodine) rather than prolonged antithyroid drug use 6, 7