What labs should be ordered for patients taking Armor Thyroid (desiccated thyroid)

Laboratory Tests for Patients Taking Armour Thyroid (Desiccated Thyroid)

For patients taking Armour Thyroid (desiccated thyroid), TSH and free T4 should be monitored every 6-8 weeks after initiating treatment until stable, then every 6-12 months for maintenance monitoring. 1

Initial and Adjustment Phase Monitoring

• TSH and free T4: These are the primary laboratory tests for monitoring thyroid replacement therapy 1, 2

  • Test 6-8 weeks after initiating treatment
  • Test 6-8 weeks after any dose adjustment
  • Target TSH within reference range (0.4-4.0 mIU/L)

• Free T3 testing: Not routinely recommended for monitoring patients on thyroid replacement therapy 3

  • Only consider if patient has persistent symptoms despite normal TSH and free T4
  • Excessive T3 levels can occur with desiccated thyroid preparations due to variable T3 content 4, 5

Maintenance Phase Monitoring

• TSH and free T4: Every 6-12 months once patient is stabilized on an appropriate dose 1, 2

• Additional laboratory tests to consider:

  • Basic metabolic panel: To monitor for potential effects on electrolytes (especially in patients with cardiac conditions) 1
  • Lipid profile: Annually to monitor cardiovascular risk factors
  • Bone density testing: Consider in patients on long-term therapy, especially if TSH is suppressed below normal range 1

Special Monitoring Considerations

• More frequent monitoring (every 2-3 months) is recommended for:

  • Elderly patients
  • Patients with cardiac disease
  • Patients with multiple comorbidities
  • Pregnancy (TSH goals change by trimester)
  • When starting medications that may interfere with thyroid hormone absorption or metabolism 1

• Signs of overtreatment to monitor:

  • Tachycardia, palpitations
  • Tremor, anxiety
  • Insomnia, heat intolerance
  • Weight loss
  • TSH suppression below 0.2 mIU/L (increases risk of atrial fibrillation and bone loss) 6

Important Considerations for Armour Thyroid

• Armour Thyroid contains both T4 and T3, with T3 levels potentially rising to supranormal values during absorption 6

• The T3 content in desiccated thyroid preparations can vary between batches, making consistent dosing challenging 4, 5

• Due to the shorter half-life of T3 compared to T4, serum levels may fluctuate more with desiccated thyroid products 6

• Laboratory testing should ideally be performed before the morning dose to obtain the most consistent results 2

• When transitioning between different thyroid preparations, more frequent monitoring is necessary until stabilization occurs 1

Remember that while desiccated thyroid is an option for thyroid replacement, most guidelines recommend levothyroxine as first-line therapy due to more consistent hormone content and more predictable laboratory values 1.