Armour Thyroid: Natural Desiccated Thyroid
Last updated: October 2026
Porcine thyroid gland extract. Contains T4 + T3 plus many other uncharacterized compounds. Some patients strongly prefer it over synthetic T4 alone. Used since the 1890s.
(1–2 grains)
T4 + T3
Decade
What Is Armour Thyroid?
Natural desiccated thyroid (NDT) is dried porcine thyroid gland. Unlike synthetic levothyroxine (T4 only), NDT contains both T4 and T3, in the proportions found in pig thyroid tissue.
Labeled for T4 and T3; FDA notes these extracts also contain many uncharacterized compounds. Per the product label, each grain (60mg) provides 38mcg T4 and 9mcg T3, roughly 4:1 by weight, and T3 is about four times as potent as T4 per microgram. The ratio reflects pig thyroid tissue, so do not read it as a match for what the human thyroid releases.
Unlike levothyroxine, NDT provides direct T3. Some patients report feeling better on it, but a blinded trial found no average difference in symptoms versus levothyroxine, so why some prefer it is not known.
Animal thyroid extracts have treated hypothyroidism since the early 1890s. Thyroxine was first synthesized in 1927 and a sodium salt was introduced in 1949, according to a review of seven decades of thyroxine treatment (PMID 31321670). Natural preparations dominated for most of the 20th century; levothyroxine alone became the standard of care after the 1970s, per a history of hypothyroidism treatment (PMID 26747302). Armour Thyroid is now distributed by AbbVie.
American Thyroid Association guidelines on treatment of hypothyroidism keep levothyroxine as the standard of care and found no consistently strong evidence that thyroid extract is superior (PMID 25266247).
What the Research Shows
FDA status: FDA says animal-derived thyroid medications, including Armour Thyroid, are not FDA approved, regulates them as biological products, and warns that tablets may not always provide the same thyroid hormone levels (FDA, unapproved thyroid medications). They remain available by prescription.
Context: Studies comparing NDT to levothyroxine show mixed results. Some patients strongly prefer NDT, but in a blinded crossover trial, symptom and cognitive scores were similar on both. The debate continues.
NDT vs Synthetic T4
- Contains T4 + T3 (plus uncharacterized compounds)
- Animal-derived (porcine)
- 4:1 T4:T3 ratio
- Batch potency problems documented (FDA-posted recalls of other NDT brands)
- Some patients prefer
- In use since the 1890s
- T4 only (prohormone)
- Synthetic (identical to human)
- No T3
- Consistent potency
- Standard of care
- Sodium salt introduced 1949
Dosing
- 1 grain (60mg) = 38mcg T4 + 9mcg T3 (label)
- Label start: 30mg (½ grain); 15mg if long-standing hypothyroidism or heart concerns
- Raise by 15mg every 2-3 weeks
- Most patients: 60-120mg/day (1-2 grains)
- No response at 180mg suggests missed doses or malabsorption (label)
- Adjust by symptoms + labs (TSH, T4)
- Take on empty stomach
- Monitor TSH after changes
- Keep iron and calcium supplements away from your dose
Key Takeaways
- Prescription drug, but not FDA-approved
- ATA guidelines keep levothyroxine as the standard of care
- Contains both T4 and T3
- Some patients strongly prefer it
- Long history of use since 1890s
- 60-120mg/day usually normalizes T4 and T3 levels (label)
- How consistent the hormone dose is from tablet to tablet (an FDA concern; other NDT brands have been recalled for potency)
- Why some patients respond better
- Optimal patient selection criteria
🛒 Recommended Products
Supplements thyroid patients often ask about. None replaces thyroid medication.
Interaction warning: taking ferrous sulfate (iron) with thyroxine raised TSH and reduced thyroxine efficacy in hypothyroid patients (PMID 1443969), and calcium carbonate taken with levothyroxine reduced its absorption (PMID 10838651). Take iron and calcium at a different time of day from your thyroid dose, and ask your doctor or pharmacist about spacing.
References
- U.S. Food and Drug Administration. FDA's Actions to Address Unapproved Thyroid Medications. fda.gov
- AbbVie. Armour Thyroid (thyroid tablets, USP) prescribing information, revised March 2024. DailyMed
- Acella Pharmaceuticals. Voluntary nationwide recall of certain lots of NP Thyroid due to sub potency (April 2021). fda.gov
- Jonklaas J, et al. Guidelines for the treatment of hypothyroidism: prepared by the American Thyroid Association task force on thyroid hormone replacement. Thyroid. 2014;24(12):1670-751. PMID 25266247
- Hoang TD, et al. Desiccated thyroid extract compared with levothyroxine in the treatment of hypothyroidism: a randomized, double-blind, crossover study. J Clin Endocrinol Metab. 2013;98(5):1982-90. PMID 23539727
- Mateo RCI, Hennessey JV. Thyroxine and treatment of hypothyroidism: seven decades of experience. Endocrine. 2019;66(1):10-17. PMID 31321670
- McAninch EA, Bianco AC. The history and future of treatment of hypothyroidism. Ann Intern Med. 2016;164(1):50-6. PMID 26747302
- Campbell NR, et al. Ferrous sulfate reduces thyroxine efficacy in patients with hypothyroidism. Ann Intern Med. 1992;117(12):1010-3. PMID 1443969
- Singh N, et al. Effect of calcium carbonate on the absorption of levothyroxine. JAMA. 2000;283(21):2822-5. PMID 10838651
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Armour Thyroid is a prescription medication. Monitor with regular TSH and T4 testing. ATA guidelines keep levothyroxine as the standard of care. Discuss options with your doctor. This is not medical advice. Not FDA-Approved Rx Required
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