Increase the Armour Thyroid dose to normalize the elevated TSH
Your patient's TSH of 6.3 mIU/L indicates inadequate thyroid hormone replacement, and the dose should be increased. The current 90 mg dose is insufficient, as evidenced by the elevated TSH above the normal reference range.
Dosing Adjustment Strategy
According to the FDA label for Armour Thyroid, most patients require 60 to 120 mg/day for maintenance, and your patient is at the lower end of this range 1. Given the TSH of 6.3 mIU/L:
- Increase the dose by 15 mg increments every 2-3 weeks until TSH normalizes 1
- Start by increasing from 90 mg to 105 mg daily
- Recheck TSH, free T4, and free T3 in 4-8 weeks after each adjustment 2
- Continue titrating until TSH reaches the normal reference range (typically 0.4-4.0 mIU/L)
Interpreting the Current Labs
The free T4 of 0.99 ng/dL appears relatively normal (assuming reference range ~0.8-1.8 ng/dL), while the total T3 of 275 ng/dL is elevated (normal range typically 80-200 ng/dL). This pattern is characteristic of desiccated thyroid preparations, which contain a 4:1 ratio of T4 to T3 by weight 2. This creates higher T3 levels relative to T4 compared to levothyroxine monotherapy 3, 4.
Key point: Despite the elevated T3, the TSH remains high, indicating the overall thyroid hormone effect is insufficient. The TSH is the primary guide for dose adjustment in primary hypothyroidism 5, 2.
Important Caveats
Age and Cardiac Considerations
- If the patient is over 50-60 years old or has any cardiac history, increase doses more cautiously (12.5 mg increments) and monitor for anginal symptoms 2
- The appearance of angina is an indication to reduce the dose 1
Compliance and Absorption Issues
Before increasing the dose, verify:
- Medication timing: Armour Thyroid should be taken 30-60 minutes before breakfast on an empty stomach for optimal absorption 2
- Interfering substances: Avoid taking with calcium, iron, proton pump inhibitors, or other medications that impair absorption 2
- Patient compliance: Failure to respond to doses of 180 mg suggests non-compliance or malabsorption 1
Monitoring Timeline
- Recheck labs 4-8 weeks after each dose change 2
- TSH may take 8 weeks or longer to plateau with smaller dose adjustments 2
- Once stable, monitor TSH every 6-12 months 2
Alternative Consideration
While guidelines recommend levothyroxine (T4) monotherapy as first-line treatment 2, if the patient specifically prefers or has been doing well on desiccated thyroid aside from the elevated TSH, continuing with dose optimization is reasonable. The elevated T3 levels seen with desiccated thyroid are expected and generally well-tolerated 6, 7, though long-term cardiovascular safety data remain limited 6.
The goal is to normalize TSH to the reference range while maintaining the patient symptom-free 5, 2. Most patients on Armour Thyroid achieve normal TSH and T4 levels with maintenance doses of 60-120 mg/day 1.