Initial Treatment for Hyperthyroidism in Non-Pregnant Females
For non-pregnant women with hyperthyroidism, antithyroid medications (methimazole or propylthiouracil), radioactive iodine ablation, or surgical thyroidectomy are the three primary treatment options, with radioactive iodine ablation being the most widely used treatment in the United States. 1
First-Line Treatment Options
The choice of initial therapy depends on the underlying cause, severity of hyperthyroidism, presence of contraindications, and patient preference 1:
Antithyroid Medications (Thionamides)
- Methimazole is the preferred antithyroid drug for non-pregnant women because it has fewer major side effects, can be administered as a single daily dose, is less expensive, and is more widely available compared to propylthiouracil 2
- Starting dose of methimazole is typically 10-30 mg as a single daily dose 2
- Propylthiouracil starting dose is 100-300 mg every 6 hours if methimazole is contraindicated 2
- Treatment duration is typically 12-18 months for the titration method, using the lowest dose that maintains euthyroidism 3
- Approximately 50% of patients experience recurrence after discontinuation of antithyroid drugs, making this a temporary solution for many patients 3, 4
Radioactive Iodine (I-131) Ablation
- This is the most widely used treatment modality in the United States for definitive management 1
- Provides permanent resolution of hyperthyroidism
- Particularly appropriate for patients at high risk of recurrence after antithyroid drugs 4
Surgical Thyroidectomy
- Reserved for specific situations including failure to respond to medical therapy, large goiters, or patient preference 1
- Provides immediate definitive treatment
Treatment Algorithm by Etiology
Graves' Disease (Most Common Cause)
- Can be treated with any of the three modalities: antithyroid drugs, radioactive iodine, or surgery 1, 4
- Long-term antithyroid drug therapy (5-10 years) is associated with lower recurrence rates (15%) compared to short-term therapy (50%) 4
- Risk factors for recurrence after 12-18 months of antithyroid drugs include: age younger than 40 years, FT4 concentrations ≥40 pmol/L, TSH-binding inhibitory immunoglobulins >6 U/L, and goiter size ≥WHO grade 2 4
Toxic Nodular Goiter
- Radioactive iodine or thyroidectomy are preferred over antithyroid drugs due to high relapse rates after drug discontinuation 4, 5
- Antithyroid drugs are not generally used long-term for this condition 5
Thyroiditis (Destructive Thyrotoxicosis)
- Usually mild and transient 4
- Beta blockers alone may be sufficient for symptom control 5
- Antithyroid drugs are not effective because the condition involves passive hormone release rather than increased synthesis 5
Symptomatic Management
Beta-adrenergic blockers (e.g., propranolol) should be used for symptomatic relief in all patients with thyrotoxicosis while awaiting definitive treatment or resolution 6, 5
Monitoring Requirements
- Thyroid function tests should be monitored periodically during antithyroid drug therapy 7
- Prothrombin time should be monitored, especially before surgical procedures, as methimazole may cause hypoprothrombinemia 7
- Monitor for agranulocytosis: if sore throat and fever develop, obtain complete blood count immediately and discontinue the thioamide 8
- Other serious side effects to monitor include hepatitis, vasculitis, and thrombocytopenia 8
Critical Pitfalls to Avoid
- Do not delay treatment of overt hyperthyroidism, as untreated disease increases mortality risk 4
- Recognize that antithyroid drugs have a 50% recurrence rate after short-term therapy; counsel patients accordingly and consider definitive therapy for high-risk patients 3, 4
- Be aware of drug interactions: methimazole may increase anticoagulant activity, and achieving euthyroid status may require dose reductions of beta blockers, digoxin, and theophylline 7
- Monitor closely for agranulocytosis, which typically presents with sore throat and fever and requires immediate drug discontinuation 8