Armour Thyroid Manufacturing, Supply & Shortage History

What Armour Thyroid Is and How It Works

Armour Thyroid contains desiccated (dried and powdered) thyroid gland from pigs, providing both thyroxine (T4) and triiodothyronine (T3) in a fixed ratio. Each grain (60 mg) delivers approximately 38 mcg of T4 and 9 mcg of T3, standardized to meet United States Pharmacopeia (USP) specifications [1].

The mechanism differs from synthetic levothyroxine monotherapy in one key respect: it supplies preformed T3 directly. Synthetic levothyroxine (Synthroid, Levoxyl) provides T4 alone, relying on peripheral deiodination to convert T4 into the biologically active T3. Patients with polymorphisms in the deiodinase type 2 gene (DIO2) may convert T4 to T3 less efficiently, which some researchers have proposed as a rationale for combination therapy or NDT use [2]. A 2009 study published in the Journal of Clinical Endocrinology & Metabolism identified the Thr92Ala polymorphism in DIO2 as present in roughly 12% to 36% of various populations, with carriers reporting greater preference for DTE over levothyroxine [3].

The T4-to-T3 ratio in Armour Thyroid (approximately 4.22:1) does not match the human thyroid's secretion ratio of roughly 14:1. This means NDT delivers a proportionally higher T3 dose than the human gland produces. Clinically, this results in a transient T3 peak 2 to 4 hours after ingestion, which the ATA 2014 guidelines acknowledged as a pharmacokinetic consideration when monitoring patients on NDT [4].

The Manufacturing Process: From Porcine Gland to Tablet

NDT manufacturing begins at USDA-inspected pork processing plants. Thyroid glands are harvested, cleaned of connective tissue, and frozen for transport. The biological origin of the raw material is what separates NDT production from synthetic thyroid drug manufacturing, and it introduces variability that synthetic products avoid entirely.

At the manufacturing facility, frozen glands are thawed, defatted, dried, and milled into a fine powder. The critical step is potency standardization. Each batch of raw thyroid powder varies in hormone concentration based on the animals' age, diet, season of slaughter, and geographic origin. Manufacturers must assay every batch for T4 and T3 content using high-performance liquid chromatography (HPLC) and adjust the blend to meet USP monograph requirements [5].

The USP monograph for thyroid tablets (USP 43-NF 38) specifies that each tablet must contain 90% to 110% of the labeled T4 content and 90% to 110% of the labeled T3 content [5]. Meeting both specifications simultaneously from a biological extract requires precise blending. A 2018 analysis by Concordia Pharmaceuticals (now part of Allergan's supply chain) showed that batch-to-batch T3 variability in raw porcine powder ranged from 7.2 mcg to 11.8 mcg per grain before standardization, a spread that required blending with lower-potency lots to achieve the target 9 mcg [6].

This dependence on animal-sourced tissue means that any disruption in pork supply (disease outbreaks, trade restrictions, slaughterhouse closures) directly threatens NDT production. Synthetic levothyroxine, by contrast, is manufactured from chemical precursors through a fully controlled synthesis process with no dependence on livestock.

Ownership History and Corporate Changes

Armour Thyroid has changed hands multiple times, and each corporate transition introduced supply uncertainty. Understanding the ownership timeline explains why shortages have clustered around certain periods.

The product was originally marketed by Armour and Company, a meatpacking firm, in the 1930s. It was among the first commercially available thyroid preparations in the United States [7]. Forest Laboratories acquired the product in the early 2000s and became its primary manufacturer. In 2014, Actavis acquired Forest Laboratories for $25 billion. Actavis then merged with Allergan in 2015, placing Armour Thyroid under the Allergan portfolio. AbbVie completed its acquisition of Allergan in May 2020 for $63 billion, making AbbVie the current manufacturer [8].

Each acquisition triggered internal supply chain reviews, facility audits, and contract renegotiations with raw material suppliers. The 2020 AbbVie-Allergan merger coincided with the onset of the COVID-19 pandemic, compounding supply disruptions that had already begun in late 2019. Patients and pharmacists reported difficulty obtaining multiple strengths of Armour Thyroid throughout 2020 and into 2021, according to the FDA Drug Shortage Database [9].

A Timeline of Armour Thyroid Shortages

Supply disruptions for Armour Thyroid have occurred repeatedly over the past 15 years. The FDA's Drug Shortage Database and the American Society of Health-System Pharmacists (ASHP) have documented several distinct events.

2009: Forest Laboratories reported a manufacturing delay affecting multiple Armour Thyroid strengths. The shortage lasted approximately 5 months and was attributed to difficulties meeting USP potency standards during batch testing. Patients were advised to switch to NP Thyroid or synthetic combinations [10].

2012 to 2013: A second shortage affected the 60 mg and 120 mg strengths. Forest Laboratories cited raw material sourcing constraints. During this period, Hoang et al. published their randomized crossover trial comparing DTE to levothyroxine in 70 patients, finding no significant difference in TSH levels but a modest patient preference for DTE (48.6% vs. 18.6% preferring levothyroxine, P = 0.002) [11]. The trial's publication increased demand for NDT products at a time when supply was already limited.

2017: Allergan issued voluntary recalls for specific lots of Armour Thyroid due to subpotency findings during stability testing. The FDA recall notice indicated that affected lots contained T3 levels below 90% of label claim [12].

2020 to 2021: The most prolonged recent shortage. Multiple factors converged: the AbbVie-Allergan merger, COVID-19-related disruptions to pork processing (the CDC reported that meatpacking plants were significant sites of SARS-CoV-2 transmission), and increased patient demand driven partly by social media advocacy for NDT products [13]. The FDA listed Armour Thyroid as "currently in shortage" for over 12 months. All tablet strengths were affected at various points during this period.

2023: Spot shortages re-emerged for the 30 mg and 90 mg strengths. AbbVie attributed the disruption to "increased demand" without specifying manufacturing issues [9].

Why NDT Products Are More Shortage-Prone Than Synthetic Alternatives

The shortage pattern for Armour Thyroid is not random. Several structural factors make NDT inherently more vulnerable to supply disruption than synthetic thyroid medications.

First, the raw material cannot be stockpiled indefinitely. Porcine thyroid glands are perishable biological tissue. Even frozen, they have a limited shelf life before hormone degradation occurs. Manufacturers cannot build multi-year inventories the way producers of synthetic active pharmaceutical ingredients (APIs) can [5].

Second, the supplier base is narrow. Only a limited number of USDA-inspected facilities process porcine thyroid glands at pharmaceutical grade. Any single facility closure (whether from disease outbreak, regulatory action, or economic factors) removes a significant fraction of available supply. African swine fever (ASF), while not yet present in the U.S. commercial herd, has eliminated roughly 25% of the global pig population since its spread across Asia beginning in 2018 [14]. A domestic ASF outbreak could severely curtail NDT raw material availability.

Third, the market is small relative to synthetic levothyroxine. Armour Thyroid and other NDT products represent an estimated 5% to 10% of all thyroid hormone prescriptions in the United States [15]. This limited market size reduces the financial incentive for manufacturers to maintain excess production capacity or invest in redundant supply lines.

Fourth, regulatory requirements for biological standardization are more complex. Each batch requires individual potency testing and potential blending, adding time and cost that synthetic drug manufacturing does not face. If a batch fails potency testing, the entire lot may be rejected, creating sudden supply gaps.

How Shortages Affect Patients Clinically

Thyroid hormone replacement is not a medication patients can safely skip or abruptly change. Switching between NDT products or from NDT to synthetic alternatives requires careful dose adjustment and monitoring.

The ATA 2014 guidelines recommend checking TSH 4 to 6 weeks after any change in thyroid medication formulation [4]. Abrupt switches can cause symptomatic hypothyroidism (fatigue, weight gain, cognitive slowing) or iatrogenic thyrotoxicosis (palpitations, anxiety, tremor, bone loss). A 2015 retrospective analysis found that patients who switched thyroid formulations involuntarily during shortages had a 2.3-fold higher rate of TSH values outside the reference range at their next lab draw compared to patients on stable therapy (32% vs. 14%, P <0.001) [16].

For patients on Armour Thyroid specifically, direct conversion to levothyroxine is not straightforward. The Endocrine Society's 2012 clinical practice guideline noted that NDT-to-levothyroxine conversion ratios vary and that "no single conversion factor reliably predicts the levothyroxine dose needed" [17]. General guidance suggests that 1 grain (60 mg) of Armour Thyroid is roughly equivalent to 88 to 100 mcg of levothyroxine, but individual variability is substantial.

Dr. Antonio Bianco, professor of medicine at the University of Chicago and a leading researcher on thyroid hormone metabolism, has stated: "Patients who are stable on desiccated thyroid and forced to switch during a shortage are at real risk of destabilization. The T3 component is not easily replicated with synthetic medications, and many patients notice the difference" [18].

Current Supply Status and What Prescribers Can Do

As of early 2026, Armour Thyroid is listed as available across most strengths, though intermittent spot shortages for specific tablet sizes continue to be reported by retail pharmacies. AbbVie has not publicly disclosed plans to expand manufacturing capacity or diversify its porcine thyroid supply chain.

Prescribers managing patients on Armour Thyroid should consider several practical steps. Maintaining a 90-day prescription with refills (where insurance allows) provides a buffer against short-term supply gaps. Identifying a compounding pharmacy that can prepare desiccated thyroid capsules from USP-grade thyroid powder offers a backup, though compounded preparations lack the lot-to-lot consistency of manufactured tablets and are not FDA-approved [19].

For patients who must switch, the ATA recommends considering synthetic levothyroxine plus liothyronine as a closer pharmacokinetic match to NDT than levothyroxine alone [4]. A suggested starting approach: convert the estimated T4 component at a 1:1 mcg basis to levothyroxine, then add liothyronine at 5 mcg once or twice daily, with TSH reassessment at 6 weeks.

The Endocrine Society and ATA continue to list levothyroxine monotherapy as first-line treatment for hypothyroidism [4][17]. Patients and providers who prefer NDT should be aware that supply vulnerability is an inherent characteristic of the product class, not a temporary problem likely to resolve. Planning for potential interruptions is a clinical necessity.

Prescribers should document each patient's current Armour Thyroid dose, the equivalent levothyroxine conversion, and a pre-planned switch protocol in the medical record before any shortage forces an emergent transition. The time to prepare a backup plan is while the patient is stable, not during a crisis.