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

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, in…