What is the recommended treatment for a patient with hyperthyroidism?

Treatment of Hyperthyroidism

First-Line Treatment: Methimazole

Methimazole is the preferred first-line antithyroid drug for treating hyperthyroidism due to its superior efficacy and safety profile, except during the first trimester of pregnancy when propylthiouracil should be used. 1

Initial Dosing Strategy

• Start methimazole at 15-20 mg/day maximum to minimize the risk of dose-dependent agranulocytosis 2
• For patients <70 years without cardiac disease, more aggressive initial dosing may be appropriate 1
• Monitor free T4 or free T3 index every 2-4 weeks during initial treatment, maintaining levels in the high-normal range using the lowest effective dose 1

Critical Safety Monitoring

• Agranulocytosis typically occurs within the first 3 months of treatment and presents with sore throat and fever, requiring immediate CBC and drug discontinuation 1
• Hepatotoxicity requires monitoring for fever, nausea, vomiting, right upper quadrant pain, dark urine, and jaundice, with immediate drug discontinuation if suspected 1
• Vasculitis can be life-threatening—watch for skin changes, hematuria, or respiratory symptoms 1

Propylthiouracil: Reserved for Specific Situations

Propylthiouracil should only be used in patients intolerant to methimazole or during the first trimester of pregnancy, due to its potential to cause severe liver failure requiring transplantation or resulting in death. 3

When to Use Propylthiouracil

• First trimester of pregnancy only (switch to methimazole after first trimester) 1, 3
• Patients with documented methimazole intolerance 3
• Thyroid storm when methimazole cannot be used 1

Propylthiouracil Safety Warnings

• Severe liver injury and acute liver failure, including fatal cases, have been reported in both adults and children 3
• Stop immediately if symptoms of hepatic dysfunction develop: anorexia, pruritus, jaundice, light-colored stools, dark urine, right upper quadrant pain 3
• Particularly dangerous in pregnant women and their infants 3

Symptomatic Management with Beta-Blockers

• Beta-blockers (atenolol 25-50 mg daily or propranolol) provide immediate symptomatic relief for tachycardia, tremor, and anxiety while awaiting thyroid hormone normalization 1
• Dose reduction needed once euthyroid state is achieved 1
• For hyperthyroidism with atrial fibrillation, beta-blockers are recommended for rate control unless contraindicated 4
• When beta-blockers cannot be used, non-dihydropyridine calcium channel antagonists (diltiazem or verapamil) are alternatives 4, 1

Definitive Treatment Options

Radioactive Iodine (I-131) Ablation

• Resolves hyperthyroidism in >90% of patients with Graves disease and toxic multinodular goiter 5
• Absolutely contraindicated in pregnancy and breastfeeding 1
• Pregnancy must be avoided for 4 months following administration 1, 6
• Potential risk of worsening Graves' ophthalmopathy 1, 6
• Most patients develop hypothyroidism within 1 year after treatment 5
• Stop antithyroid drugs at least one week prior to radioiodine to reduce risk of treatment failure 2

Surgical Thyroidectomy

• Treatment of choice for patients with compressive symptoms from obstructive goiter 5
• Rarely used in Graves disease unless radioiodine refused or large symptomatic goiter present 6
• Should be performed as (near) total thyroidectomy 2

Treatment Duration and Remission Criteria

• Antithyroid drugs typically prescribed for 12-18 months for Graves disease with view to inducing long-term remission 6
• If TSH receptor antibodies remain >10 mU/L after 6 months of antithyroid treatment, remission is unlikely and radioiodine or thyroidectomy should be recommended 2
• Antithyroid drugs will not cure hyperthyroidism associated with toxic nodular goiter 6

Special Considerations for Specific Causes

Graves Disease

• If rhythm control strategy is selected, thyroid function must be normalized prior to cardioversion to reduce risk of recurrence 4
• Antiarrhythmic drugs and direct current cardioversion are generally unsuccessful while thyrotoxicosis persists 4
• Anticoagulation based on CHA₂DS₂-VASc risk factors, not solely by presence of hyperthyroidism 1

Toxic Nodular Goiter

• Radioiodine is the treatment of choice 6
• Antithyroid drugs do not induce remission but can control hyperthyroidism temporarily 6

Destructive Thyroiditis

• Self-limited condition requiring different management 1
• Beta-blockers for symptomatic relief during hyperthyroid phase 1
• No indication for antithyroid drugs 1

Critical Drug Interactions

• Warfarin dose adjustments needed due to increased anticoagulation effect when taking antithyroid drugs 1, 3
• Beta-blockers may need dose reduction when patient becomes euthyroid 1, 3
• Theophylline clearance decreases when euthyroid—reduced dose may be needed 1, 3
• Digoxin levels may increase when hyperthyroid patients become euthyroid 3

Common Pitfalls to Avoid

• Never reduce methimazole based solely on suppressed TSH while free T4 remains elevated or high-normal—this leads to inadequate treatment and recurrent hyperthyroidism 1
• Do not use propylthiouracil as first-line therapy due to severe hepatotoxicity risk 3, 2
• Avoid starting radioiodine without stopping antithyroid drugs at least one week prior 2
• Never attempt cardioversion in thyrotoxic patients without first achieving euthyroid state 4