When is Armour thyroid (desiccated thyroid) considered as a treatment option for hypothyroidism?

Armour Thyroid (Desiccated Thyroid) in Hypothyroidism Treatment

Armour thyroid (desiccated thyroid) should only be considered as a treatment option for hypothyroidism in patients who have unambiguously not benefited from standard levothyroxine (LT4) therapy despite normalized TSH levels. 1

Standard Treatment Approach

• Levothyroxine (LT4) remains the first-line treatment for newly diagnosed hypothyroid patients 1
• LT4 offers several advantages:
  • Once-daily administration due to long half-life
  • Stable hormone levels
  • Extrathyroidal conversion of T4 to T3 remains operative 2

When to Consider Armour Thyroid

Appropriate Candidates:

• Patients who remain symptomatic despite:
  • Normalized TSH levels on LT4
  • Adequate trial of LT4 optimization
  • Exclusion of other causes of persistent symptoms 1

Clinical Evidence Supporting Use:

• Some patients experience significant symptomatic benefit and improved quality of life with desiccated thyroid after failing to respond to LT4 3
• In one study, EQ-5D-5L utility scores increased from 0.214 to 0.606 after 6 months of NDT treatment in LT4-unresponsive patients 3

Risks and Concerns with Armour Thyroid

Inconsistent T3 Content:

• Desiccated thyroid products remain outside formal FDA oversight
• Consistency of T4 and T3 contents is monitored only by manufacturers 1

Potential Adverse Effects:

• Fixed T4:T3 ratio (approximately 4:1) may cause transient T3 elevations 2
• Palpitations may occur during absorption phase due to supranormal T3 values 2
• Risk of overtreatment: approximately 25% of patients on thyroid replacement may be inadvertently maintained on doses high enough to make TSH undetectable 4

Serious Risks of Overtreatment:

• Increased risk for osteoporosis, fractures, and cardiovascular complications 4
• Potential for atrial fibrillation, especially in elderly patients 4
• Accelerated bone mineral density loss 4

Monitoring and Management

Dosing Considerations:

• Starting dose should be individualized based on patient's weight and severity of hypothyroidism
• The mean daily dose of desiccated thyroid needed to normalize serum TSH contains approximately 11 mcg T3 1
• Some patients may require higher doses

Monitoring Protocol:

• Check TSH levels every 6-8 weeks during dose titration 4
• Target TSH within reference range (0.45-4.5 mIU/L) 4
• Once stable, monitor every 6-12 months 4

Special Populations at Higher Risk:

• Elderly patients (>60 years) are more sensitive to thyroid hormone effects 4
• Patients with cardiovascular disease are at increased risk for atrial fibrillation 4
• Postmenopausal women have higher risk for decreased bone mineral density and fractures 4

Clinical Pitfalls to Avoid

1. Self-administration without medical supervision: Can lead to serious adverse events including cardiovascular complications 5

2. Failure to monitor TSH regularly: Essential to prevent overtreatment and associated risks

3. Inappropriate patient selection: Armour thyroid should not be first-line therapy for hypothyroidism but reserved for those who fail standard treatment

4. Drug interactions: Medications that alter absorption (antacids, calcium supplements, iron) can impact optimal dosing 4

5. Abrupt discontinuation: Can lead to hypothyroid symptoms; dose adjustments should be gradual

By following these guidelines, Armour thyroid can be considered as a second-line option for carefully selected patients who have not achieved symptomatic relief with standard levothyroxine therapy.