Armour Thyroid FDA Approval History

Is Armour Thyroid FDA approved?

No. The current label says so in its own text: Armour Thyroid (thyroid tablets, USP) "has not been approved by FDA as a new drug" [1]. FDA's enforcement page says the same thing in plainer words: "Animal-derived thyroid medications are not FDA approved" [2].

That separates Armour Thyroid from the synthetic thyroid hormones. Levothyroxine and liothyronine have been FDA-approved for decades and are marketed as branded and generic products [2].

What FDA says about animal-derived thyroid today

FDA describes these products as made from dried, ground animal thyroid glands, usually porcine. It lists Armour Thyroid alongside NP Thyroid, Nature-Thyroid and Natural Thyroid, notes that they are available by prescription only, and estimates that 1.5 million patients received prescriptions for them from U.S. outpatient retail and mail-order pharmacies in 2024 [2]. An estimated 22 million patients received levothyroxine prescriptions that same year [2].

FDA's stated concerns are specific: the products "have not been reviewed by FDA to ensure the safety, purity and potency"; tablets made from the same manufacturing batches may not always provide the same thyroid hormone levels; there is an increased risk of certain impurities from the animal source or the way it is manufactured; and they "contain many compounds that are uncharacterized for safety and effectiveness" [2]. The agency says it has received complaints from patients and reports of adverse events related to safety and potency [2].

Has FDA banned Armour Thyroid, or set a removal date?

No. FDA told manufacturers, importers and distributors of unapproved animal-derived thyroid medications that it intends to issue two draft guidances: one on its compliance priorities and one on developing these products to support marketing applications [3]. In a notice dated 2026-08-05, the agency said those drafts are still being completed and that it "will continue applying its general, risk-based enforcement approach to unapproved ADT products, giving enforcement priority to products that pose the highest risk to public health," while firms seek approval of marketing applications [3]. FDA's page says it may take action against a manufacturer that is not meeting quality standards [2].

FDA has announced no ban and no removal date. The products remain on the market and are still being labeled and dispensed [3][2].

Enforcement actions that did happen

FDA's warning letter to RLC Labs, dated 2020-10-09, followed an inspection at the company's Phoenix facility from February 20 to March 5, 2020. The letter found current good manufacturing practice violations, determined that WP Thyroid and Nature-Throid were adulterated, and stated that none of the company's products was the subject of an approved biologics license application [5].

Acella Pharmaceuticals recalled one lot of NP Thyroid 15 (15 mg) and one lot of NP Thyroid 120 (120 mg) on 2020-09-17 because testing found them sub-potent, with a product that could contain as low as 87% of the labeled amount of levothyroxine [6]. The notice lists the signs and symptoms of under-treated hypothyroidism a patient could experience and says Acella had received four reports of adverse events for those lots possibly related to the recall [6].

Can a compounding pharmacy make desiccated thyroid?

Under FDA's stated position, no. FDA says unapproved animal-derived thyroid medications are not eligible for compounding because they are regulated as biological products under the Public Health Service Act [2].

What the Armour Thyroid label covers

The label lists two uses: replacement or supplemental therapy in patients with hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis, and pituitary TSH suppression in the treatment or prevention of euthyroid goiters, thyroid nodules, subacute or chronic lymphocytic thyroiditis (Hashimoto's), multinodular goiter and thyroid cancer [1].

The label carries the thyroid hormone class boxed warning: these drugs have been used for obesity, but in euthyroid patients doses within the range of daily hormonal requirements are ineffective for weight reduction, and larger doses may produce serious or even life-threatening toxicity, particularly when given with sympathomimetic amines such as those used for their anorectic effects [1].

Armour Thyroid is supplied as 15, 30, 60, 90, 120, 180, 240 and 300 mg tablets, and the labels state 38 mcg of levothyroxine (T4) and 9 mcg of liothyronine (T3) per grain of thyroid [1]. The T4 to T3 ratio in desiccated thyroid is about 4.2:1, against about 14:1 for the hormones secreted by the human thyroid gland, so the extract has a relative excess of T3 and can produce supraphysiologic serum T3 levels that peak shortly after a dose [4].

What the guidelines and trials say

The American Thyroid Association's 2014 guideline makes a strong recommendation, based on moderate-quality evidence, that levothyroxine be considered routine care for patients with primary hypothyroidism in preference to thyroid extracts [4]. FDA notes that professional medical society guidelines recommend synthetic levothyroxine as the preferred treatment for hypothyroidism [2].

In the randomized, double-blind crossover trial by Hoang and colleagues, 70 adults with primary hypothyroidism spent 16 weeks on desiccated thyroid extract and 16 weeks on levothyroxine, in either order. There were no differences in symptoms or neurocognitive tests. Weight was 3 lb lower on the extract (172.9 vs 175.7 lb, P<.001), and 48.6% preferred the extract, 18.6% preferred levothyroxine and 32.9% had no preference [8].

A later three-arm crossover trial by Shakir and colleagues randomized 75 hypothyroid patients to levothyroxine, levothyroxine plus liothyronine, or desiccated thyroid extract for 22 weeks. TSH stayed in range in all arms, and there were no differences in the primary outcomes apart from a minor increase in heart rate on the extract [9].