Home › Trials › NCT06345339

Comparing Armour Thyroid to Synthetic T4 for Treating Hypothyroidism

A Phase 2/3 Multicenter, Double Blinded, Randomized, Dose-conversion, Active Control Study Examining the Efficacy and Safety of Armour Thyroid Compared to Synthetic T4 for the Treatment of Adults With Primary Hypothyroidism

PHASE2; PHASE3 · AbbVie · NCT06345339

This study is testing whether switching from synthetic T4 to Armour Thyroid can help adults with hypothyroidism feel better while they are already stable on their current medication.

Quick facts

PhasePHASE2; PHASE3
Study typeInterventional
Enrollment2800 (estimated)
Ages18 Years to 75 Years
SexAll
SponsorAbbVie (industry)
Locations139 sites (Birmingham, Alabama and 138 other locations)
Trial IDNCT06345339 on ClinicalTrials.gov

What this trial studies

This study evaluates the safety and efficacy of Armour Thyroid compared to synthetic T4 in adults with primary hypothyroidism who are currently stabilized on synthetic T4. Participants must have been on a stable dose of synthetic T4 for at least 12 months prior to the study. The trial aims to assess the effectiveness of switching from synthetic T4 to Armour Thyroid therapy. It includes both Phase 2 and Phase 3 evaluations to ensure comprehensive assessment of treatment outcomes.

Who should consider this trial

Good fit: Ideal candidates are adults diagnosed with primary hypothyroidism who have been on stable synthetic T4 therapy for at least 12 months.

Not a fit: Patients with conditions affecting the absorption or metabolism of thyroid medications may not benefit from this study.

Why it matters

Potential benefit: If successful, this study could provide a more effective treatment option for patients with primary hypothyroidism.

How similar studies have performed: Other studies have explored similar comparisons between Armour Thyroid and synthetic T4, indicating potential for meaningful insights.

Eligibility criteria

Show full inclusion / exclusion criteria 
Inclusion Criteria:

* Have a diagnosis of primary hypothyroidism made \>= 12 months prior to Screening.
* Be on continuous thyroid replacement therapy of synthetic T4 for primary hypothyroidism for at least 12 months immediately prior to the Screening Visit.
* Be on a stable FDA-approved daily dose of synthetic T4 prior to the Screening visit, and must be taking synthetic T4 dose of at least 25 mcg at Screening visit. Must enter the study using the same stable dose to determine dose conversion.
* Documentation of 1 in-range thyroid-stimulating hormone (TSH) (i.e., within 0.45 - 4.12 mIU/L, inclusive) at Screening and at least 1 additional in range TSH (i.e., within 0.45 - 4.12 mIU/L, inclusive) taken at a minimum of 6 weeks and a maximum of 12 months prior to Screening.

Exclusion Criteria:

* Any clinical condition or previous surgery that might affect the absorption, distribution, biotransformation, or excretion of Armour Thyroid or synthetic T4.
* History of alcohol or other substance abuse within the previous 6 months prior to the Screening.
* Known or suspected allergy or intolerance to any ingredients of Armour Thyroid, including its excipients, synthetic T4, other thyroid replacement medications, or pork products.

Where this trial is running

Birmingham, Alabama and 138 other locations

+89 more sites — see ClinicalTrials.gov for the full list.

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.

View on ClinicalTrials.gov →

Conditions: Hypothyroidism, Armour Thyroid, Synthetic T4

Last reviewed 2026-05-15 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.