Is Desiccated Thyroid (Armour, NP Thyroid) Better Than Levothyroxine?

The short answer: No. In blinded trials, desiccated thyroid extract (DTE) did not beat levothyroxine for symptoms, quality of life, or memory as a group. The American Thyroid Association says levothyroxine should stay the standard of care. DTE products such as Armour Thyroid and NP Thyroid are not FDA-approved, and some lots have been recalled for low potency. A small group of people who still feel unwell on levothyroxine may prefer a product with T3, which is a talk to have with your clinician.

What is desiccated thyroid, and how is it different from levothyroxine?

Desiccated thyroid is dried, powdered thyroid gland from pigs. It contains two hormones: thyroxine (T4) and triiodothyronine (T3). Levothyroxine is a lab-made copy of T4 only. Your body turns T4 into the active hormone T3 as needed.

The Armour Thyroid label on DailyMed lists 38 mcg of T4 and 9 mcg of T3 in each 1-grain (60 mg) tablet. The same label says T3 is "approximately four times as potent" as T4, microgram for microgram. A 2020 review in the journal Thyroid puts the T4 to T3 ratio in DTE at about 4 to 1.

Human biology works differently. The American Thyroid Association patient page notes that "the balance of T4 and T3 in animals is different from the human thyroid." In a 1990 tracer study of healthy adults, the thyroid made 3.3 mcg of T3 per day per square meter of body surface. The rest of the body made 12.7 mcg by converting T4. So about four-fifths of daily T3 comes from conversion, not from the gland. That is the reasoning behind T4-only treatment. If you want the basics of the synthetic option first, see our levothyroxine guide.

What do head-to-head trials show?

Two randomized, double-blind crossover trials from Walter Reed National Military Medical Center are the best direct evidence. In each one, patients tried each treatment without knowing which pill they took.

• 2013 trial, 70 patients. Hoang and colleagues gave DTE or levothyroxine for 16 weeks each. They found "no differences in symptoms and neurocognitive measurements." Patients lost 3 lb on DTE. Still, 48.6% preferred DTE, 18.6% preferred levothyroxine, and 32.9% had no preference.
• 2021 trial, 75 patients. Shakir and colleagues compared levothyroxine, levothyroxine plus T3, and DTE for 22 weeks each. TSH stayed in range on all three. There were no differences in the main outcomes, apart from a minor rise in heart rate on DTE. Treatment preference did not differ for the group as a whole.

The 2021 trial had one notable subgroup result. The third of patients with the most symptoms on levothyroxine preferred and did better on a treatment that contained T3. That group improved on symptom, quality-of-life, and depression scores. This is a subgroup finding, so it needs confirmation.

A 2018 online survey of 12,146 people, published in Thyroid, found higher satisfaction among people who took DTE. Among respondents without other health conditions, median satisfaction was 7 out of 10 on DTE and 5 on levothyroxine. A survey cannot show cause, and people chose their own treatment. The authors said the design "does not provide a mechanistic explanation."

What does the American Thyroid Association recommend?

The 2014 ATA guidelines for the treatment of hypothyroidism concluded that "levothyroxine should remain the standard of care." The task force found "no consistently strong evidence for the superiority" of alternatives, including thyroid extract. It called for long-term trials of combination therapy and thyroid extracts. This summary relies on the published abstract.

The ATA patient page adds two practical points. First, "the amounts of both T4 and T3 can vary in every batch," which makes steady blood levels harder. Second, "animal thyroid extract should not be used in pregnancy, as the T3 portion does not reach the developing baby." Our article on how pregnancy changes thyroid targets covers dosing needs during pregnancy.

Is desiccated thyroid FDA-approved?

No. The Armour label on DailyMed carries this statement: "This drug has not been found by FDA to be safe and effective, and this labeling has not been approved by FDA." An FDA consumer update says "the agency has not approved medicines containing DTE."

FDA's position has shifted over the past year:

• August 6, 2025. FDA sent a notice to manufacturers saying it intends to act against these products. FDA said they legally require a biologics license, and none has one. The letter estimated that 1.5 million patients (about 6%) received DTE in 2024. FDA said patients might need up to 12 months to switch to an approved product.
• March 11, 2026. FDA told manufacturers it planned draft guidance "before August 2026" on its compliance priorities.
• August 5, 2026. In a follow-up letter, FDA said it "continues its work to complete these draft guidances." Meanwhile, it applies a "risk-based enforcement approach."

As of September 2026, DTE is still sold by prescription. The FDA page on unapproved thyroid medications advises patients who take these products to talk to their doctor.

Have desiccated thyroid products been recalled?

Yes. On April 29, 2021, Acella Pharmaceuticals recalled 38 lots of NP Thyroid. Testing found tablets with "less than 90% of the labeled amount" of T3 and/or T4. The recall covered 15, 30, 60, 90, and 120 mg strengths. Acella had received 43 reports of serious adverse events possibly linked to the recall.

The recall notice listed the risks of a weak tablet. These include fatigue, feeling cold, constipation, and hair loss. It also noted a "reasonable risk of serious injury" in newborns and pregnant women. The 2020 review in Thyroid adds that DTE contents are "monitored by the manufacturers only."

Who might consider a T3-containing option?

The 2020 review says newly diagnosed patients "should be treated with LT4." It suggests a trial of synthetic levothyroxine plus liothyronine for people who "have unambiguously not benefited" from levothyroxine. Note that this is a synthetic combination, not DTE.

Before any switch, rule out other causes of ongoing symptoms. Our guide on why you may still have symptoms with a normal TSH walks through them. Symptoms like fatigue and low mood overlap with many conditions, and symptom.md can help you track them for your visit. Do not change or stop thyroid medicine on your own. Any switch needs follow-up blood tests.

The bottom line

Levothyroxine is FDA-approved, has a consistent dose, and remains the ATA's standard of care. Blinded trials found no overall advantage for desiccated thyroid, though some patients prefer it. DTE is not FDA-approved, its T3 share is higher than the human body makes, and potency recalls have happened. FDA still allows its sale while it drafts guidance.

Last updated: September 2026. This article is for informational purposes only and does not constitute medical advice. Talk with your doctor or endocrinologist before changing thyroid medication.