Question: what is the difference between synthroid and armour thyroid?
Answer: More specifically, Armour is known as an NDT medication, short for Natural Desiccated Thyroid, and it is porcine-derived from the thyroid glands of pigs. 3. Synthroid contains T4 (thyroxine) only, whereas Armour contains both T4 and T3 (tri-iodothyronine). T3 is more biologically active than T4.