Hyperthyroidism Treatment
Primary Treatment Modalities
For most patients with hyperthyroidism, treatment should begin with methimazole as the first-line antithyroid drug, combined with beta-blockers for immediate symptom control, with definitive therapy (radioactive iodine or surgery) reserved for specific indications. 1, 2
Antithyroid Drug Therapy
Methimazole is the preferred first-line agent due to superior efficacy and safety profile compared to propylthiouracil 2. The starting dose should not exceed 15-20 mg daily to minimize the risk of dose-dependent agranulocytosis 3.
Propylthiouracil should be reserved exclusively for:
- Patients intolerant to methimazole 4
- First trimester of pregnancy only 2, 4
- This restriction exists because propylthiouracil can cause severe liver failure requiring transplantation or resulting in death 4, 3
Symptomatic Management
Beta-blockers (atenolol 25-50 mg daily or propranolol) should be initiated immediately for symptomatic relief of tachycardia, tremor, and anxiety while awaiting thyroid hormone normalization 1, 2. These can be continued until thioamide therapy reduces thyroid hormone levels to the therapeutic range 1.
Definitive Treatment Options
Radioactive Iodine (I-131) Ablation
Radioactive iodine is the most widely used treatment in the United States and represents definitive therapy for most cases 5.
Key considerations:
- Absolutely contraindicated in pregnancy and breastfeeding 2
- Pregnancy must be avoided for 4 months following administration 2, 6
- May worsen Graves' ophthalmopathy; corticosteroid cover may reduce this risk 2, 6
- Antithyroid drugs should be stopped at least one week prior to radioiodine to reduce treatment failure risk 3
- Nearly all patients develop hypothyroidism requiring lifelong thyroid hormone replacement 1
Specific indications:
- Toxic nodular goiter (treatment of choice) 3, 6
- Graves' disease when TSH-receptor antibodies remain above 10 mU/L after 6 months of antithyroid treatment 3
Surgical Thyroidectomy
Near-total or total thyroidectomy is recommended for:
- Large goiters causing compressive symptoms 1, 3
- Suspicious nodules requiring evaluation 1
- Severe ophthalmopathy 1
- Patients who refuse or have contraindications to radioiodine 6
Surgery requires lifelong thyroid hormone replacement post-operatively 1.
Treatment Duration and Monitoring
Initial monitoring should occur every 2-4 weeks during antithyroid drug therapy, with the goal of maintaining free T4 or free thyroxine index in the high-normal range using the lowest effective dose 1, 2.
For Graves' disease treated with antithyroid drugs:
- Standard course is 12-18 months 6, 5
- Recurrence occurs in approximately 50% of patients after short-term treatment 7
- Long-term treatment (5-10 years) is associated with fewer recurrences (15%) compared to short-term treatment 7
Predictors of recurrence after antithyroid drug discontinuation:
- Age younger than 40 years 7
- FT4 concentrations 40 pmol/L or higher 7
- TSH-binding inhibitory immunoglobulins higher than 6 U/L 7
- Goiter size equivalent to or larger than WHO grade 2 7
Critical Safety Monitoring
Agranulocytosis
Typically occurs within the first 3 months of thioamide treatment and presents with sore throat and fever 2. Immediate CBC and drug discontinuation are required 2.
Hepatotoxicity
Particularly with propylthiouracil, monitor for fever, nausea, vomiting, right upper quadrant pain, dark urine, and jaundice 2, 4. Immediate drug discontinuation is mandatory if suspected 2.
Vasculitis
Can be life-threatening, requiring vigilance for skin changes, hematuria, or respiratory symptoms 2, 4.
Special Clinical Scenarios
Thyroiditis-Induced Hyperthyroidism
This is self-limited and resolves spontaneously within weeks 1. Treatment focuses on symptomatic management with beta-blockers only; antithyroid drugs are not indicated 1, 2. Most patients transition to primary hypothyroidism requiring close monitoring and eventual thyroid hormone replacement 1.
Pregnancy
During first trimester, propylthiouracil is preferred despite hepatotoxicity risk 2, 4. After first trimester, switch to methimazole 2. The goal is maintaining FT4 in the high-normal range using the lowest possible dose 1. Monitor FT4 every 2-4 weeks during pregnancy 1. Women treated with either drug can breastfeed safely 1.
Severe Hyperthyroidism/Thyroid Storm
Mandatory hospitalization and endocrine consultation are required 1. Aggressive management includes beta-blockers, high-dose antithyroid drugs, hydration, supportive care, and consideration of additional therapies including steroids, saturated solution of potassium iodide (SSKI), or possible surgery 1.
Subclinical Hyperthyroidism
For TSH <0.1 mIU/L due to Graves or nodular thyroid disease, treatment should be considered, particularly for patients older than 60 years or those with increased risk for heart disease, osteopenia, or osteoporosis 8. For TSH 0.1-0.45 mIU/L, routine treatment is not recommended for all patients due to insufficient evidence of adverse outcomes 8.
Drug Interactions
Warfarin requires dose adjustment due to increased anticoagulation effect when taking antithyroid drugs 2. Beta-blockers may need dose reduction once euthyroid 2. Theophylline clearance decreases when euthyroid 2.