Abstract: Novel formulations useful for thyroid hormone replacement and suppression therapy are described herein. While dosage formulations containing iodinated thyronines, levothyroxine sodium (T4) or liothyronine sodium (T3), as the active pharmaceutical ingredient (API) dispersed in a polymeric solid are known, manufacturing such formulations with acceptable dose content uniformity is difficult due to the high biological activity of T4 and T3. Described herein is the preparation of a single API formulation containing both T4 and T3 in a pharmaceutically effective ratio, wherein the dose content uniformity is the same for T3 as for T4 even if the T3 dose is extremely low.