Armour Thyroid Cost vs. Alternatives: A Price and Evidence Comparison

Are Armour Thyroid and Levothyroxine Approved Differently?

Yes. FDA states that animal-derived thyroid medications, sold as Armour Thyroid, NP Thyroid, Nature-Thyroid and Natural Thyroid among other names, are not FDA approved, while levothyroxine and liothyronine have been FDA-approved for decades [4]. The Armour Thyroid label states that the product has not been approved by FDA as a new drug [5].

In 2024, an estimated 1.5 million patients received prescriptions for animal-derived thyroid medications through U.S. outpatient retail and mail-order pharmacies, compared with about 22 million patients for levothyroxine [4]. Both types are available by prescription only [4].

What the Alternatives Are

Levothyroxine supplies T4 alone, liothyronine supplies T3 alone, and desiccated thyroid supplies both — 38 mcg of levothyroxine and 9 mcg of liothyronine per 60 mg (one grain) tablet [5]. That is about 4.2 parts T4 to 1 part T3, against roughly 14 to 1 from the human thyroid gland, so desiccated thyroid can produce T3 levels above normal shortly after a dose [3]. The tablets also carry unmeasured amounts of other thyroid compounds, including diiodothyronine, monoiodothyronine and calcitonin [3]. The American Thyroid Association's 2014 guideline recommends levothyroxine as routine care for primary hypothyroidism in preference to thyroid extracts, a strong recommendation based on moderate-quality evidence [3].

Do the Trials Show an Advantage?

A 2013 randomized, double-blind crossover trial enrolled 70 adults aged 18 to 65 with primary hypothyroidism on stable levothyroxine for six months, giving 16 weeks of desiccated thyroid and 16 weeks of levothyroxine in either order [1]. Symptoms and neurocognitive tests did not differ between periods [1]. Weight was 3 lb lower on desiccated thyroid, at 172.9 versus 175.7 lb (P<.001) [1]. At the end, 34 patients (48.6%) preferred desiccated thyroid, 13 (18.6%) preferred levothyroxine, and 23 (32.9%) had no preference [1]. The authors reported no significant quality-of-life improvement [1].

A later three-treatment crossover trial randomized 75 hypothyroid patients to levothyroxine, levothyroxine plus liothyronine, or desiccated thyroid for 22 weeks [2]. TSH stayed in the reference range in all arms, and the trial found no difference in its primary outcomes; heart rate was slightly higher with desiccated thyroid [2]. Treatment preference did not differ overall [2].

Potency Problems in This Drug Class

FDA's warning letter of October 9, 2020 to RLC Labs, maker of Nature-Throid and WP Thyroid, reported that 6 of 10 samples were sub-potent for at least one active ingredient [6]. Acella Pharmaceuticals recalled NP Thyroid 15 mg and NP Thyroid 120 mg lots on September 17, 2020 for sub-potency, with a product possibly containing as low as 87% of the labeled levothyroxine [7].