Synthroid is the most popular thyroid hormone replacement drug on the market. It contains levothyroxine, the more abundantly produced of the two thyroid hormones. Endocrinologists widely endorse Synthroid for the treatment of hypothyroidism but it does come with a number of serious side effects and limitations. In addition I also give some practical advice on how to switch from T4 only medications like Levothyroxine to Natural Desiccated thyroid medications like Armour thyroid. In general I recommend. All of these conditions may reduce the effectiveness of Synthroid because they may limit your body's natural ability to convert T4 into the active thyroid hormone T3. Does this make sense? So some people may be able to take T4 thyroid hormone but may have difficulty in activating the hormone once it is absorbed into the body. Nature-Throid Synthroid® T4/T3 T4 120 mg (2 grain) Levothyroxine Sodium 105 mg (15 mg + 90 mg) 15 mg (1/4 grain) Desiccated Porcine Thyroid Extract I am currently a user of synthroid. My sister, who is a health nut, keeps insisting that I get my doctor to prescribe armour thyroid, because its natural, I don't see how dried pig thyroids are natural, but I aksed my doctor about it and he would not so much as talk to me about it. See the top 10 most prescribed drugs in the U.S. by doctors and get natural cures and alternative medicine remedies for pain relief, lower blood pressure, lower cholesterol, insomnia and more. Changing from Synthroid to the equivalent armour gave me palpitations, so I went back to after a visit to a cardiologist. Is there a way to gradually switch that will prevent this? Armour Thyroid is classified “natural” in that it is thyroid hormone extracted from pigs, whereas Synthroid is considered “artificial” in that it is a synthetically engineered chemical. There is much controversy surrounding Armour Thyroid and Synthroid, especially when compared head-to-head. Natural Alternatives for Synthroid Synthroid is hormone replacement used to treat hypothyroidism, a condition in which the thyroid gland does not produce enough hormones. Synthroid is also used to treat or prevent goiter, or an enlarged thyroid gland.