What is the next step for a 68-year-old man with Hashimoto's thyroiditis who is not responding to Synthroid (levothyroxine) treatment?

Management of Non-Response to Levothyroxine in Hashimoto's Thyroiditis

For a 68-year-old man with Hashimoto's thyroiditis not responding to Synthroid (levothyroxine), the next step should be to evaluate for medication absorption issues, adjust dosing, or consider alternative formulations such as levothyroxine sodium oral solution. 1, 2

Initial Assessment for Non-Response

When a patient with Hashimoto's thyroiditis is not responding to levothyroxine therapy, consider the following algorithm:

1. Verify medication adherence

   • Confirm the patient is taking levothyroxine correctly:
     • On an empty stomach
     • 30-60 minutes before breakfast
     • Separated from other medications, especially those containing calcium, iron, or antacids

2. Laboratory assessment

   • Check both TSH and Free T4 levels 1
   • Consider morning laboratory testing (around 8 am) for accurate results 1
   • Determine if TSH is still elevated despite therapy

3. Evaluate for absorption issues

   • Assess for comorbid gastrointestinal conditions that may affect absorption:
     • Gastritis
     • Gastroparesis
     • Small intestinal bacterial overgrowth (SIBO)
     • Celiac disease 2
   • Review medications that may interfere with levothyroxine absorption:
     • Proton pump inhibitors
     • Calcium supplements
     • Iron supplements
     • Antacids

Intervention Options

Dose Adjustment

• If TSH remains elevated, consider dose adjustment based on current levels 1
• For patients under 70 without cardiac disease: target dose 1.6 mcg/kg/day
• For elderly patients (like this 68-year-old): more cautious dosing with target TSH 1.0-4.0 mIU/L 1

Alternative Formulations

• Consider switching to levothyroxine sodium oral solution (Tirosint-SOL) which has better absorption in patients with GI conditions 2
• This formulation contains only three ingredients (levothyroxine, water, and glycerol) which may improve tolerance and absorption 2

Medication Administration Modification

• Crushing tablets may improve absorption in patients with high expression of efflux transporters 3
• Consider administering levothyroxine at bedtime (at least 3 hours after the last meal) as an alternative

Reassessment of Thyroid Function

• After any intervention, monitor thyroid function (TSH and Free T4) at 6-8 weeks 1
• Continue adjustments until target TSH is achieved
• For this 68-year-old patient, target TSH should be 1.0-4.0 mIU/L as recommended for elderly patients 1

Consider Recovery Testing

• Some patients with Hashimoto's thyroiditis (approximately 20%) may recover thyroid function 4
• Consider testing for recovery using TRH stimulation test if clinically indicated, though this is less common in practice today 4

Important Caveats

• Overtreatment with levothyroxine increases risk of atrial fibrillation and osteoporosis, particularly concerning in elderly patients 1
• Avoid rapid dose escalation in elderly patients or those with cardiac conditions
• Be aware that malabsorption of levothyroxine is common in patients with Hashimoto's thyroiditis who have comorbid GI conditions 2
• If the patient remains unresponsive despite appropriate interventions, consider referral to an endocrinologist for specialized evaluation