How does it compare to synthetic T4?

NDT contains both T4 and T3 (ratio ~4:1), plus other thyroid hormones (T2, T1) and calcitonin. Some patients report feeling better on NDT than synthetic T4 alone, though studies are mixed.

Standardized by T4 content: 60mg (1 grain) = 38mcg T4 + 9mcg T3. Typical dose: 60-120mg (1-2 grains). Some patients prefer 2-3 grains. Dose titrated by symptoms and TSH.

Why do patients prefer it?

Some patients feel NDT provides better symptom relief than T4 alone — particularly energy, mood, and temperature regulation. May be due to T3 content or other hormones in the extract.

Does the ATA recommend it?

No — the American Thyroid Association (ATA) doesn't recommend NDT as first-line therapy. They cite lack of consistent benefit over levothyroxine and concerns about variable hormone batch content.

Is Armour FDA approved?

Armour Thyroid is FDA-approved as a thyroid medication (since before current FDA standards). It grandfathered in and is available by prescription.

Natural Desiccated Thyroid • FDA Approved

Armour Thyroid: Natural Desiccated Thyroid

Q: What is Armour Thyroid?

Armour Thyroid is natural desiccated thyroid (NDT) — dried porcine thyroid gland. Contains T4, T3, T2, T1, and calcitonin. Derived from animal thyroid (pig), not synthetic.

By MeetPeptide Research Team

Last updated: March 2026

Porcine thyroid gland extract. Contains T4 + T3 + T2 + T1 + calcitonin. Some patients strongly prefer it over synthetic T4 alone. Used since the 1890s.

Typical Dose
(1–2 grains)

Contains Both
T4 + T3

First Use
Decade

Background

What Is Armour Thyroid?

Natural desiccated thyroid (NDT) is dried porcine thyroid gland. Unlike synthetic levothyroxine (T4 only), NDT contains multiple thyroid hormones in their natural proportions.

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Complete Hormone Profile

Contains T4, T3, T2, T1, and calcitonin. The T4:T3 ratio is approximately 4:1 by weight, closer to human thyroid secretion than T4 alone.

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Active T3 Included

Unlike levothyroxine, NDT provides direct T3. This may explain why some patients feel more energy and better mood on NDT — no reliance on conversion.

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Long History

NDT was the only thyroid treatment from the 1890s until synthetic T4 was developed in the 1950s. Armour Thyroid (from Forest Pharmaceuticals) is the best-known brand.

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ATA Position

The American Thyroid Association doesn't recommend NDT as first-line. They cite variable hormone batch content and lack of consistent superiority over levothyroxine.

Research

What the Research Shows

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Context: Studies comparing NDT to levothyroxine show mixed results. Some patients strongly prefer NDT, but objective measures (TSH, thyroid function) often show similar outcomes. The debate continues.

Patient Preference (Surveys)

Significant portion of NDT users prefer it to synthetic T4

30-50%

Objective Improvement (Studies)

Similar TSH normalization and thyroid markers vs levothyroxine

Similar

ATA Recommendation

First-line therapy — levothyroxine (not NDT)

No NDT

Comparison

NDT vs Synthetic T4

Natural Desiccated (Armour)

Contains T4 + T3 + T2 + T1
Animal-derived (porcine)
4:1 T4:T3 ratio
Variable between batches (theoretically)
Some patients prefer
~120 years of use

Synthetic Levothyroxine

T4 only (prohormone)
Synthetic (identical to human)
No T3
Consistent potency
Standard of care
Since 1950s

Protocol

Dosing

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Dosing in Grains

1 grain (60mg) = 38mcg T4 + 9mcg T3
Start: 30-60mg (½-1 grain)
Typical: 60-120mg (1-2 grains)
Some go to 90-120mg (1.5-2 grains)
Titrate by symptoms + TSH

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Timing

Take on empty stomach
Divide dose if needed (T3 component)
Some split AM/PM for stability
Monitor TSH after changes

Bottom Line

Key Takeaways

✅ What We Know

FDA-approved medication (grandfathered in)
Contains both T4 and T3
Some patients strongly prefer it
Long history of use since 1890s
Works well for many patients

⚠️ What We Don't Know

ATA doesn't recommend as first-line
Batch-to-batch variability (theoretical)
Why some patients respond better
Optimal patient selection criteria

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⚠️ Disclaimer

Armour Thyroid is a prescription medication. Monitor with regular TSH and Free T3 testing. Not recommended as first-line by ATA guidelines. Many patients do well on it — discuss with your doctor. This is not medical advice. FDA Approved Rx Required