A pharmaceutical composition comprising thyroxine, acacia, and an antioxidant selected from propyl gallate, butylated hydroxyanisol, and butylated hydroxytoluene is disclosed. The pharmaceutical composition has an improved shelf life. In one embodiment, the composition additionally comprises sucrose, microcrystalline cellulose, and mannitol. The pharmaceutical composition may be used for treating thyroid disorders by orally administering the composition to a patient in need thereof.