Initial Treatment for Hypothyroidism
The initial treatment for hypothyroidism is levothyroxine (T4) replacement therapy, with dosing based on patient characteristics and severity of disease. 1, 2
Diagnosis and Initiation of Treatment
Treatment is indicated for:
- Patients with TSH >10 mIU/L (overt hypothyroidism)
- Patients with elevated TSH and low free T4 levels
- Women with subclinical hypothyroidism who are pregnant or planning pregnancy 1
Diagnosis requires laboratory confirmation:
- Elevated TSH with low free T4 indicates overt primary hypothyroidism
- Multiple tests over 3-6 months are recommended to confirm abnormal findings 1
Levothyroxine Dosing Guidelines
Initial dosing should be tailored to patient-specific factors:
| Population | Starting Dose | Target TSH Range |
|---|---|---|
| Adults <70 years without cardiac disease | 1.6 mcg/kg/day | 0.5-2.0 mIU/L |
| Elderly patients (>60 years) or those with cardiac conditions | 25-50 mcg/day | 1.0-4.0 mIU/L |
| Pregnant women | Adjusted to restore TSH to reference range | 0.5-2.0 mIU/L |
Monitoring and Dose Adjustments
- Measure TSH and free T4 within 6-8 weeks after initiating treatment
- Once stabilized, monitor TSH annually to avoid overtreatment or undertreatment 2
- For pregnant women:
Special Considerations
Elderly Patients
- Start with lower doses (12.5-50 mcg/day) due to increased risk of cardiovascular complications
- Overtreatment can increase risk of atrial fibrillation and osteoporosis 1, 4
Cardiac Patients
- Use lower starting doses in patients with known or suspected ischemic heart disease
- Development of low TSH on therapy suggests overtreatment 1
Pediatric Patients
- Rapid restoration of normal T4 levels is essential for preventing adverse effects on cognitive development
- Initiate therapy immediately upon diagnosis
- Monitor closely during first 2 weeks for cardiac overload and arrhythmias 4
Common Pitfalls to Avoid
Overtreatment: Can lead to atrial fibrillation, cardiac dysfunction, and osteoporosis, particularly in elderly patients 1
Inadequate monitoring: Failure to check TSH levels 6-8 weeks after initiation or dose changes can result in under or overtreatment 2
Combination therapy: Adding liothyronine (T3) to levothyroxine is not recommended as first-line treatment, even in patients with persistent symptoms and normal TSH levels 3, 5
Medication interactions: Certain medications and dietary supplements can interfere with levothyroxine absorption, requiring dose adjustments
Discontinuing treatment: Levothyroxine is generally continued for life in patients with permanent hypothyroidism 4