What is the initial management for hyperthyroidism?

Management of Hyperthyroidism

The initial management of hyperthyroidism depends on the underlying etiology, but for most cases of Graves' disease and toxic nodular goiter, treatment should begin with antithyroid drugs (methimazole preferred), beta-blockers for symptomatic control, and close monitoring of thyroid function tests every 2-4 weeks. 1, 2

Initial Diagnostic Workup

Before initiating treatment, confirm the diagnosis and determine the etiology:

• Measure TSH and free T4 (FT4) to confirm biochemical hyperthyroidism (suppressed TSH with elevated FT4) 3, 4
• Check T3 levels in highly symptomatic patients with minimal FT4 elevations 1
• Obtain TSH-receptor antibodies to diagnose Graves' disease 1, 4
• Perform thyroid scintigraphy if thyroid nodules are present or etiology is unclear 3
• Physical examination should specifically assess for diffuse goiter, thyroid bruit, or ophthalmopathy (which are diagnostic of Graves' disease and warrant early endocrine referral) 1

First-Line Pharmacologic Management

Antithyroid Drug Therapy

Methimazole is the preferred first-line antithyroid drug for most patients with hyperthyroidism:

• Initial dosing for methimazole: 15 mg daily for mild hyperthyroidism, 30-40 mg daily for moderate hyperthyroidism, and 60 mg daily for severe hyperthyroidism, divided into 3 doses at 8-hour intervals 2
• Maintenance dosing: 5-15 mg daily once euthyroid state is achieved 2
• Methimazole is superior to propylthiouracil because it has fewer major side effects, can be given as a single daily dose, is less expensive, and more rapidly induces euthyroidism 5, 6
• Starting doses should not exceed 15-20 mg/day to minimize the dose-dependent risk of agranulocytosis 5

Propylthiouracil should be reserved for specific situations:

• First trimester of pregnancy (due to methimazole's association with aplasia cutis and choanal/esophageal atresia) 1, 2, 7
• Patients who have experienced adverse reactions to methimazole 5
• Critical warning: Propylthiouracil can cause severe liver failure requiring transplantation or resulting in death 5

Beta-Blocker Therapy for Symptom Control

Initiate beta-blockers immediately to control symptoms while waiting for antithyroid drugs to take effect:

• Atenolol 25-50 mg daily or propranolol are appropriate choices 1
• Titrate to heart rate <90 bpm if blood pressure allows 1
• Beta-blockers provide rapid improvement in cardiac, neurologic, and other symptoms 1
• Continue until thyroid hormone levels normalize 1

Monitoring Strategy

Close surveillance is essential during initial treatment:

• Monitor free T4 or FTI every 2-4 weeks initially to adjust dosing 1
• Goal is to maintain FT4 in the high-normal range using the lowest possible thioamide dose 1
• Check TSH and free T4 after 6-8 weeks once on stable dosing 1
• Monitor for transition to hypothyroidism every 2-3 weeks after diagnosis, as this is the most common outcome for thyroiditis-induced hyperthyroidism 1

Critical Safety Monitoring

Patients must be counseled to report immediately:

• Sore throat and fever (agranulocytosis warning signs) - obtain complete blood count immediately and discontinue thioamide 1, 2
• New rash, hematuria, decreased urine output, dyspnea, or hemoptysis (vasculitis symptoms) 2
• Other side effects include hepatitis, thrombocytopenia 1

Laboratory monitoring:

• Prothrombin time should be monitored, especially before surgical procedures, as methimazole may cause hypoprothrombinemia 2
• Thyroid function tests periodically during therapy 2

Special Populations

Pregnancy

• Propylthiouracil is preferred in the first trimester due to methimazole's teratogenic risks 1, 2, 7
• Consider switching to methimazole for second and third trimesters given propylthiouracil's hepatotoxicity risk 2
• Monitor closely as thyroid dysfunction often diminishes during pregnancy, allowing dose reduction or discontinuation 2
• Both drugs are compatible with breastfeeding with appropriate monitoring 1, 2

Elderly Patients with Cardiovascular Disease

• Start with lower doses of thyroid replacement if hypothyroidism develops (25-50 mcg rather than full 1.6 mcg/kg dose) 1
• Beta-blockers are particularly important as cardiovascular complications are the chief cause of death in older patients with hyperthyroidism 1

Treatment Duration and Definitive Therapy

• Standard course: 12-18 months of antithyroid drugs, though recurrence occurs in approximately 50% of patients 4
• Long-term treatment (5-10 years) is associated with fewer recurrences (15%) compared to short-term treatment 4
• Consider definitive therapy (radioiodine or thyroidectomy) if TSH-receptor antibodies remain >10 mU/L after 6 months of treatment, as remission is unlikely 5
• Toxic nodular goiter should ultimately be treated with radioiodine or thyroidectomy 5, 4
• Stop antithyroid drugs at least one week before radioiodine to reduce risk of treatment failure 5

Common Pitfalls to Avoid

• Do not use propylthiouracil as first-line except in first trimester pregnancy or methimazole intolerance 5
• Do not use radioactive iodine (I-131) in pregnant women - it is absolutely contraindicated 1
• Do not overlook drug interactions: Hyperthyroidism increases clearance of beta-blockers and theophylline; becoming euthyroid may require dose reductions of these medications and digitalis 2
• Do not assume all hyperthyroidism requires antithyroid drugs: Thyroiditis-induced thyrotoxicosis is self-limited and typically requires only supportive care with beta-blockers 1