Management of Hashimoto's Thyroiditis
Levothyroxine (LT4) replacement therapy is the cornerstone of Hashimoto's thyroiditis management when hypothyroidism develops, with dosing typically ranging from 1.4-1.8 mcg/kg/day based on preserved thyroid function and lean body mass. 1, 2
Diagnosis and Evaluation
- Check TSH and Free T4 levels for diagnosis and monitoring
- Test for thyroid peroxidase antibodies (TPOAbs) to confirm autoimmune etiology
- Consider thyroid ultrasound to evaluate thyroid structure and volume
Treatment Algorithm Based on Thyroid Function
1. Overt Hypothyroidism (Elevated TSH with Low Free T4)
- Initiate levothyroxine therapy:
- Standard starting dose: 1.4-1.8 mcg/kg/day 2
- For patients under 70 without cardiac disease: Target TSH 0.5-2.0 mIU/L 1
- For elderly patients or those with cardiac conditions: Start with lower doses (25-50 mcg/day) and target TSH 1.0-4.0 mIU/L 1
- For pregnant women: Target TSH 0.5-2.0 mIU/L with dose adjustments as needed 1
2. Subclinical Hypothyroidism (Elevated TSH with Normal Free T4)
- For TSH >10 mIU/L: Initiate levothyroxine therapy
- For TSH 4-10 mIU/L: Consider treatment based on:
- Presence of symptoms
- TPO antibody status
- Age (more conservative approach in elderly)
- For elderly patients with TSH <10 mIU/L, treatment has not shown benefits in randomized trials 1
3. Euthyroid Hashimoto's (Normal TSH and Free T4 with positive antibodies)
- Monitor TSH every 6-12 months to assess for progression to hypothyroidism 1, 3
- More frequent monitoring (every 1-2 years) for patients with positive TPO antibodies 1
4. Hashitoxicosis (Initial hyperthyroid phase)
- Manage symptoms with beta-blockers (e.g., atenolol or propranolol) 4, 3
- Monitor for transition to hypothyroid phase, which commonly follows
Medication Administration Guidelines
- Take levothyroxine on an empty stomach, 30-60 minutes before breakfast 1
- Avoid taking within 4 hours of calcium supplements, iron, or antacids 1
- Maintain consistent brand of levothyroxine to avoid fluctuations in bioavailability 1
Monitoring and Dose Adjustment
- Check TSH and Free T4 levels 6-8 weeks after initiating therapy or changing dose 1
- Increase dose by 12.5-25 mcg if TSH remains above target range 1
- Decrease dose if TSH falls below reference range 1
- Once stable, monitor TSH every 6-12 months 1, 3
Special Considerations
- Pregnancy: Increased thyroid hormone requirements; use only levothyroxine (T3 does not sufficiently cross fetal blood-brain barrier) 2
- Goiter management: Long-term LT4 treatment can help control thyroid volume; significant decreases in thyroid volume have been observed in patients on LT4 therapy 5
- Vitamin D status: Consider assessment as patients with Hashimoto's thyroiditis often have lower vitamin D levels, which may influence inflammatory markers 6
Potential Complications and Monitoring
- Monitor for signs of overtreatment (iatrogenic thyrotoxicosis), which can increase risk for osteoporosis, fractures, or cardiac issues 1
- Be aware of increased risk of papillary thyroid cancer (1.6 times higher) and thyroid lymphoma (60 times higher) compared to general population 2
- For women of reproductive age, note that TPOAbs are associated with 2-4 fold increased risk of recurrent miscarriages and preterm birth 2