This study will evaluate the efficacy and safety of Armour Thyroid treatment compared with synthetic T4 in subjects who have primary hypothyroidism and are currently stabilized (i.e., in-range thyroid-stimulating hormone \[TSH\]) on synthetic T4 treatment. This study will also therefore evaluate the efficacy and safety of dose conversion from synthetic T4 therapy to Armour Thyroid therapy.
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.
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.
Parallel
Armour Thyroid
DrugOral Capsule or Tablet
Levothyroxine
DrugOral Capsule
Percentage of Participants who Achieve Thyroid-Stimulating Hormone (TSH) Response
TSH response is defined as TSH values falling within 0.45 to 4.12 mIU/L (inclusive). TSH response will be determined at Week 55 and at a prior visit with no out-of-range TSH values in between (response rate is tested against a specified non-inferiority margin).
Number of Participants with Adverse Events (AEs)
An AE is defined as any untoward medical occurrence in a patient or clinical investigation in which a participant is administered a pharmaceutical product which does not necessarily have a causal relationship with this treatment.
Percentage of Participants who Achieve TSH Response
TSH response is defined as TSH values falling within 0.45 to 4.12 mIU/L. TSH response will be determined at Week 55 and at a prior visit with no out-of-range TSH values in between (response rate is tested against a specified non-inferiority margin \[stricter than the one used in the Primary Outcome Measure\]).
Number of Participants Needing Altered Dose Conversion from Synthetic T4 to Armour Thyroid
Number of participants needing altered dose conversion from synthetic T4 to Armour Thyroid.
Frequency of Dose Titrations During the Double-Blind (DB) Period Among Participants who Achieved TSH Response at the End of the DB Period
Frequency of dose titrations (0,1,2...) during the DB period among participants who achieved TSH response at the end of the DB period.
