Armour Thyroid Formulation Difference Between New and Old

Most people take Synthroid for thyroid hormone replacement. This is a synthetic product (also called levothyroxine) and consists primarily of the thyroid hormone called T4. Most all traditional doctors use this type of hormone exclusively. However, most natural medical doctors use the desiccated thyroid gland which contains all the thyroid hormones (primarily T4 and T3, but also some T1 and T2).

The most common brand of desiccated thyroid is made by Forest pharmaceuticals and is called Armour thyroid as it was previously made by the Armour company.

There were changes to the Armour Thyroid formulation. These changes were made in 1996. We had purchased the former Armour thyroid products (Armour Thyroid, Thyrolar, and Levothroid) from another drug company in 1991. The prior company continued to manufacture the Armour Thyroid for us through 1996. At that time, they had fallen behind on production, so Forest decided to end their contract manufacturing agreement & make the product in our own plant. We had occasionally experienced problems with the product NOT disintegrating & dissolving quickly enough, so we added a better, more proven disintegrate to the formulation at that same time.


  • Thyroid Powder USP
  • Anhydrous Dextrose
  • Mineral Oil NF
  • Calcium Stearate, NF


  • Thyroid Powder USP
  • Anhydrous Dextrose
  • Microcrystalline Cellulose
  • Sodium Starch Glycolate NF
  • Calcium Stearate NF
  • Opadry White (titanium dioxide)

The dextrose is derived from cornstarch, but as you can see, that was also in the older formulation. (No change there) The micro- crystalline cellulose is derived from wood pulp. It is a standard diluent (as is the dextrose), but also helps in disintegration. The sodium starch glycolate is derived from potato starch. It acts as both a binder and a disintegrant. The opadry white (titanium dioxide) is a white mineral (not a dye), that gives the tablet consistent color from lot to lot. The calcium stearate is derived from beef tallow, but again it was also in the older formulation. (No change there)

Therefore, Armour Thyroid tablets do NOT have a "corn syrup coating". The dextrose, which is the only ingredient from a corn source, was also contained in the prior formulation. As to the decreased effectiveness mentioned in the attached Internet posting, I have spoken to hundreds of similar patients that were on every possible thyroid product or combination of products. There are other factors that effect the thyroid hormone activity in the human body. The most common interference in activity is from changing estrogen levels in women. The higher the estrogen level is in the bloodstream, the more 'bound' to plasma proteins the thyroid hormone is. Every woman that I've spoken to that thinks that she 'got a impotent batch', etc., has just begun experiencing menopausal symptoms or just started on an estrogen tablet, patch, or cream. When their thyroid dose is adjusted in response to this change, they are right back to normal again. (This is directly out of the drug interaction section of our package insert...)

To try to address the other issues mentioned, Armour Pharmaceuticals does not exist any more. Forest Pharmaceuticals makes Armour Thyroid now. It is the only natural, desiccated thyroid product that we make. (The other two are synthetic.) Again, there is no syrup coating on the tablets. The often rapid 'change' in effectiveness experienced by patients on any thyroid product is almost always 'patient specific', not 'product specific'. The patient has almost always begun a new season of life or changed something else (eg, adding another drug product) in his or her life, diet, or drug regimen. I hope this addresses your question(s) completely. Please do NOT hesitate to reply or call with any further questions or comments.

Daryl Wesche, RPh Drug Information Associate

Professional Affairs Department Forest Pharmaceuticals, Inc.

(800) 678-1605, Ext. 7301 Email Forest Pharmaceuticals

Dr. Mercola's Comments:
Many patients have noticed that they did not do as well with Armour thyroid. There is another option to obtain desiccated thyroid and that is to purchase it from a compounding pharmacist. The advantage of this preparation is that there are no binders as they come in capsules. If one seems to be having problems with Armour thyroid and the advanced thyroid blood tests are normal, then one should consider trying the compounded version.


For more information on how to determine with conventional blood work if you need thyroid click here. These tests are far more sophisticated than the traditional blood work that most doctors order and also the temperature testing that many physicians recommend.

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