Desiccated Thyroid Extract (Armour Thyroid / NP Thyroid)

Desiccated thyroid extract (DTE) — available as Armour Thyroid and NP Thyroid — is a thyroid hormone replacement derived from dried porcine (pig) thyroid glands. It contains both T4 and T3, making it distinct from standard levothyroxine therapy. While the American Thyroid Association (ATA) does not recommend DTE as first-line treatment, it recognizes that DTE is the treatment of choice for a carefully selected subset of patients. This article summarizes exactly what the ATA guidelines say, who may benefit, what the risks are, and what you need to know following recent FDA regulatory activity.

What Is Desiccated Thyroid Extract?

Desiccated thyroid extract is made by removing moisture from the thyroid glands of pigs, standardizing the material for iodine content, and pressing it into tablets. It has been used to treat hypothyroidism since the late 1800s — well before synthetic thyroid hormone was developed.

The main brands are:

• Armour Thyroid — manufactured by AbbVie (formerly Allergan/Forest), derived from porcine thyroid
• NP Thyroid — manufactured by Acella Pharmaceuticals, also porcine-derived

Both contain both T4 (levothyroxine) and T3 (liothyronine) in an approximately 4:1 ratio by weight. This is different from the physiologic T4:T3 ratio secreted by the human thyroid gland, and the T3 content is considered by many endocrinologists to be suprathysiologic relative to what the human thyroid would normally produce. Each grain (60–65 mg) of DTE provides approximately 38 mcg T4 and 9 mcg T3.

FDA Regulatory Status — September 2025 Update

In August 2025, the FDA issued letters to DTE manufacturers signaling their intent to remove DTE from the market unless manufacturers submit formal New Drug Applications (NDAs) under section 505 of the Federal Food, Drug & Cosmetic Act. The FDA's stated concern is the unregulated nature of DTE products — there is currently no regulatory guarantee of consistent potency, bioavailability, or purity from batch to batch.

The ATA responded in September 2025 with a public statement affirming that:

• The ATA supports patient access to all safe and effective therapies for hypothyroidism
• DTE remains the treatment of choice for some patients, and the ATA recognizes patient autonomy in treatment selection
• The ATA is working with the FDA, manufacturers, and patient organizations to ensure DTE remains available through a proper regulatory pathway
• Patients currently on DTE should not make changes to their medication without speaking to their physician

This situation is evolving. Patients currently taking Armour Thyroid or NP Thyroid should discuss the implications with their endocrinologist at their next visit.

ATA Guideline Position on DTE

The primary ATA reference is: Jonklaas J, Bianco AC, et al. "Guidelines for the Treatment of Hypothyroidism." Thyroid. 2014;24(12):1670–1751. (The primary ATA hypothyroidism treatment guidelines — the most recent comprehensive version as of 2026.)

The ATA 2014 guidelines state the following regarding DTE:

The 2025 ATA Statement further clarified that while DTE is not first-line, "the ATA recognizes that it is the treatment of choice for some patients" and supports the principle of personalized patient therapy.

Key points from the ATA guidelines regarding DTE:

• LT4 monotherapy is the standard first-line treatment — this has not changed
• No randomized controlled trial has consistently demonstrated DTE to be superior to levothyroxine
• A 2013 trial (Hoang et al.) found that DTE was preferred by some patients over LT4 and was associated with modest weight loss in those who preferred it
• DTE contains a fixed T4:T3 ratio that may not be optimal for every patient; the T3 component is typically higher than what the human thyroid naturally provides
• DTE is considered a second-line option, appropriate in a limited subset of patients after discussion of risks and benefits

Who May Benefit — Limited Patient Selection

DTE is not appropriate for most patients. Based on ATA guidelines and clinical experience, patients who may be candidates for a trial of DTE include:

• Patients with persistent hypothyroid symptoms despite optimal levothyroxine dosing — confirmed by a normal TSH in the optimal range, with other causes of symptoms excluded
• Patients who have been on levothyroxine for a sufficient duration (typically 3–6 months) without symptom improvement
• Patients with evidence of impaired T4-to-T3 conversion — such as low Total T3 despite a normal TSH, possibly related to DIO2 genetic variants
• Patients who express a strong, informed preference for DTE after understanding the risks and limitations, and who are able to participate in close monitoring

Risks and Limitations of DTE

Understanding the risks is essential before considering DTE therapy. These include:

• Suprathysiologic T3 peaks: Because DTE contains a fixed ratio of T3, patients may experience temporarily elevated T3 levels after each dose — potentially causing palpitations, anxiety, tremor, or insomnia, particularly at higher doses
• Batch-to-batch variability: Unlike FDA-regulated levothyroxine, DTE potency can vary between manufacturing lots, making stable dosing more challenging
• Elevated T3 and bone loss: Long-term excess thyroid hormone — particularly T3 — can accelerate bone resorption and increase fracture risk. Monitoring bone density is important in patients on DTE long-term
• Cardiovascular risk: Elevated T3 can increase heart rate and cardiac workload. Patients with underlying heart disease require particular caution
• No long-term outcomes data: Unlike levothyroxine, which has decades of clinical trial data, there are no large long-term studies of DTE demonstrating safety or superiority in outcomes such as cardiovascular events, fractures, or quality of life
• Regulatory uncertainty: The 2025 FDA action creates uncertainty about long-term availability

Monitoring on DTE Therapy

Patients on DTE require more frequent and detailed monitoring than those on levothyroxine alone. The ATA recommends:

• TSH and Total T3 should both be measured — TSH alone is insufficient on DTE because T3 suppresses TSH independently of T4 levels
• Total T3 should ideally remain within the normal reference range; persistently elevated T3 suggests the dose is too high
• TSH should not be suppressed below normal (unless there is a specific clinical reason, such as thyroid cancer surveillance)
• Monitoring frequency: every 6–8 weeks after dose changes; every 6 months once stable
• Bone density (DEXA scan) should be monitored in patients on long-term DTE, particularly postmenopausal women
• Clinical assessment at each visit for signs of excess (palpitations, tremor, weight loss, insomnia) or deficiency (fatigue, cold intolerance, constipation)

DTE and Pregnancy — Not Recommended

Both the ATA and the AACE/ATA joint guidelines explicitly state that DTE (and combination T4/T3 therapy) should not be used during pregnancy. The reasons include:

• DTE causes lower serum T4 levels, and fetal brain development in the first trimester depends on adequate maternal T4 transport across the placenta
• The fixed T4:T3 ratio cannot be adjusted to meet the specific demands of pregnancy
• The T3 component does not cross the placenta in meaningful amounts — it is T4 that the fetus relies on

Women of childbearing age who are on DTE and are considering pregnancy should discuss switching to levothyroxine with their endocrinologist before conception. If pregnancy is discovered while on DTE, transition to levothyroxine should occur as early in the first trimester as possible.

Our Clinical Approach at District Endocrine

At District Endocrine, our providers — including Dr. Anis Rehman, MD, Dipl. ABOM and Dr. Sana Akbar, MD — have extensive clinical experience managing patients on desiccated thyroid extract, including Armour Thyroid and NP Thyroid. We follow ATA guidelines in our approach:

• Levothyroxine remains our first-line recommendation for all patients with hypothyroidism, consistent with ATA and AACE/ATA guidelines
• For patients who have not responded adequately to optimized levothyroxine therapy and meet appropriate criteria, we are willing to discuss a supervised trial of DTE through shared decision-making
• We provide thorough informed consent — including the lack of FDA approval, the regulatory uncertainty following the 2025 FDA announcement, the absence of long-term outcome data, and the specific risks of T3 excess
• We monitor all DTE patients with both TSH and Total T3 to ensure therapy remains within the therapeutic window
• We do not prescribe DTE for patients who are pregnant, planning pregnancy, have significant cardiovascular disease, or have active bone disease without careful evaluation