Is Armor thyroid (desiccated thyroid) as effective as having no thyroid function?

Armour Thyroid Is Not Equivalent to Standard Thyroid Hormone Replacement for Hypothyroidism

Armour thyroid (desiccated thyroid extract) is not recommended as first-line therapy for hypothyroidism and cannot be considered equivalent to having no thyroid function, as it lacks standardization and poses potential risks compared to synthetic levothyroxine.

Standard of Care for Hypothyroidism Treatment

Synthetic levothyroxine (LT4) is the standard treatment for hypothyroidism according to current guidelines, for several important reasons:

• LT4 has a long half-life allowing once-daily dosing
• Provides stable hormone levels without fluctuations
• Allows for precise dosing adjustments based on TSH levels
• Extrathyroidal conversion of T4 to T3 remains fully operative 1

Monitoring and Dosing of Standard Therapy

• TSH is the primary monitoring tool with high sensitivity (98%) and specificity (92%) 2
• Target TSH levels should be individualized based on risk:
  • For thyroid cancer patients with residual disease: <0.1 mU/L
  • For disease-free low-risk patients: slightly below or within normal range 2
• Mean LT4 dose required is typically 1.6 mcg/kg/day 1

Concerns with Armour Thyroid (Desiccated Thyroid Extract)

Desiccated thyroid extract (DTE) products like Armour Thyroid have several significant limitations:

1. Inconsistent T3 content: DTE remains outside formal FDA oversight with consistency of T4 and T3 contents monitored only by manufacturers 3

2. Supraphysiologic T3 levels: Serum T3 frequently rises to supranormal values in the absorption phase, associated with palpitations 1

3. Fixed T4:T3 ratio: DTE contains a fixed LT4/LT3 ratio of approximately 4:1, which doesn't allow for individualized adjustment of each hormone 3

4. Potential safety concerns: Case reports have documented serious adverse events, including myocardial infarction in a patient self-administering Armour Thyroid 4

Limited Evidence for DTE Use

While some studies suggest potential benefits of DTE in specific scenarios:

• A 2021 study showed improvement in quality of life measures in levothyroxine-unresponsive patients switched to NDT 5
• However, this was a small, non-randomized study without a control group

The majority of clinical guidelines do not support routine use of DTE:

• Clinical guidelines recommend LT4 as first-line therapy for newly diagnosed hypothyroid patients 3
• Only consider combination therapy with LT4+LT3 for patients who have unambiguously not benefited from LT4 3

Potential Risks of Inappropriate DTE Use

• Increased risk of cardiovascular events (2-3 times higher) through propagation of a hypercoagulable state 4
• Bone demineralization with long-term thyroid hormone excess 2
• Cardiac tachyarrhythmias and symptoms of thyrotoxicosis 2

When to Consider Alternative Therapies

If a patient remains symptomatic on appropriate LT4 therapy with normalized TSH:

1. First confirm proper LT4 administration and absorption
2. Rule out other causes of persistent symptoms
3. Consider a trial of combination therapy (LT4+LT3) under close supervision 3
4. Start by reducing LT4 dose by 25 mcg/day and adding 2.5-7.5 mcg LT3 once or twice daily 3

Conclusion

Armour thyroid cannot be considered equivalent to having no thyroid function, as it provides an inconsistent and potentially harmful approach to thyroid hormone replacement. Synthetic levothyroxine remains the standard of care for hypothyroidism treatment due to its safety profile, consistent dosing, and extensive clinical evidence supporting its use.