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The Claim: Synthroid is the Best Thyroid Hormone Replacement Drug

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Updated: February 22, 2007

The Claim: Synthroid is the Best Thyroid Hormone Replacement Drug
Question: The Claim: Synthroid is the Best Thyroid Hormone Replacement Drug

If you are hypothyroid, your doctor will probably prescribe Synthroid. This levothyoxine (synthetic thyroxine) drug, made by Abbott Labs, is the top-selling thyroid drug in the U.S., commanding some two-thirds of the market for thyroid replacement. Synthroid is, however, often more costly than its competitors.

Some doctors won't hear of prescribing anything but Synthroid however, and claim unequivocally that "Synthroid is the best."

Is That So?

Answer: Levothyroxine is the synthetic form of T4, one of the two main hormones the thyroid produces. The most widely prescribed levothyroxine product is the brand name Synthroid.

Given that levothyroxine is the conventional medical world's accepted treatment for hypothyroidism, most patients will find themselves prescribed levothyroxine, and usually Synthroid.

Synthroid's manufacturer has at times claimed their drug to be better than its competitors, but research proved Synthroid to be merely bioequivalent -- or equal, in terms of what function they perform in the body -- to their competition, rather than better. This claim of superiority, therefore, actually has no merit.

Many doctors, however, still erroneously believe that Synthroid is "better," after being subject to years of this misleading advertising message.

All the major brandname levothyroxine products, Synthroid, Unithroid, Levoxyl and Levothroid, have different fillers and binders, so people may have different allergic responses to the different brands. So, if you react to one levothyroxine, your doctor might want to try other brands to see if you react to those brands as well.

Some people who are on levothyroxine also need the addition of the second key hormone, T3. Among that group, some people do best with the T3 drug Cytomel. Anecdotally, however, some patients have reported allergic reactions to Cytomel. The option, compounded or time-released compounded T3, has been used successfully by other patients, but there have been concerns about these products, due to inconsistent production. Other doctors and patients prefer a product known as Thyrolar, a synthetic combination of T4 and T3.

Some patients do best on natural desiccated thyroid drugs, such as Armour thyroid, or, in some cases, people find the hypoallergenic formula of natural drug, Nature-throid, works best for them. (Pork allergies, however, may make these products problematic for some patients. There are some patients and practitioners who are also concerned about these products due to fears of prion-related diseases such as Mad Cow Disease, despite manufacturer assurances that these products are safe.)

So is Synthroid, or any thyroid drug, better than the others? I think Dr. Richard Shames, a Boca Raton, Florida holistic practitioner and co-author of Thyroid Power and Fat, Fuzzy and Frazzled? -- who has treated thyroid conditions for a quarter century -- has the best advice for patients.

"In 25 years of practice, I have found that it doesn't necessarily matter which kind of thyroid hormone you start with so much, as which kind you end up with after trying several different types to see which one works best for you. Initially, I typically recommend whatever type they have either heard about, have a "gut-feeling" about, know family members who have a good response to a particular kind of medicine, or have a philosophical inclination for one kind or another. Sometimes it it the combination of two or three of the above medicines that proves to be the magic solution for a particular person. If the initial item tried does not give 85-95% improvement, I then encourage the person to either add something to their first choice product or discontinue it and start something totally new. It is my firm belief that the state of the art in finding the optimal medicine is still trial and error."

The answer is, the best drug is the drug which safely makes you feel your best. And there's no predetermined formula to tell which drug will be the best for you, until you try them, find optimal doses, and see how you do over time.

Mary Shomon, About.com's Thyroid Guide since 1997, is a nationally-known patient advocate and best-selling author of 10 books on health, including "The Thyroid Hormone Breakthrough: Overcoming Sexual and Hormonal Problems at Every Age," "The Thyroid Diet: Manage Your Metabolism for Lasting Weight Loss," "Living Well With Hypothyroidism: What Your Doctor Doesn't Tell You...That You Need to Know," "Living Well With Graves' Disease and Hyperthyroidism," "Living Well With Autoimmune Disease," and "Living Well With Chronic Fatigue Syndrome and Fibromyalgia." Click here for more information on Mary Shomon.

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