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Response from TPA to the Statement from British Thyroid Foundation (BTF) about Armour Thyroid to USP

Cc. British Thyroid Association, NHS Endocrinologists, All General Practitioners, Society of Endocrinology

The British Thyroid Foundations (BTF) views on Armour are extremely disappointing and misleading. Nowhere has any statement been backed with a reference. We have corrected their misleading information below and demand that the BTF make the necessary corrections immediately. (The BTF response is in italics)

Armour Thyroid is a brand of natural desiccated thyroid extract made by Forest Laboratories in the United States.

“Natural desiccated thyroid tablets are made from raw pork thyroid glands collected at slaughterhouses, which are tested for absence of Salmonella and E. coli, then held in a frozen state until they are delivered to the processing laboratory where they are minced, placed in a vacuum dryer, defatted, then milled to a fine powder before being packaged. Samples are tested for chemical and microbiological characteristics.

The manufacturer state that the following are the ingredients of Armour: Active ingredients: T3 and T4. Inactive ingredients: calcium state, dextrose, microcrystalline cellulose, sodium starch and opadry white.

Armour Thyroid is a natural preparation of USP grade desiccated thyroid powder derived from porcine (pork) thyroid glands. Armour Thyroid meets all the requirements set by the United States Pharmacopoeia (USP) for thyroid medications and manufacturing specifications are tightly controlled, contrary to the BTFs current misconceptions about desiccated thyroid. The natural porcine thyroid powders are not sterile products nor are they designed to be such. The finished lots are tested for and meet all USP compendial requirements including those for the absence of Salmonella and E.coli pathogens. They also verify that the Total Aerobic Plate Count (TAPC) does not exceed 10,000 Colony Forming Units per gram (CFU/g). The entire thyroid process is performed in accordance with FDA Current Good Manufacturing Practices (cGMP) requirements. After processing, the thyroid products are packaged, stored, and handled in a manner to prevent any cross-contamination.

The disease status of porcine animals born, raised, and slaughtered in the USA or Canada can be accessed through the World Health Organization, Office Internationale des Epizooties (OIE) web site at There you will find that the USA and Canada are classified as being free of List A porcine diseases including foot-and-mouth disease, hog cholera, swine vesicular disease, and African swine fever. This disease information can also be confirmed through USDA Animal Plant and Health Inspection Service (APHIS)

Armour Thyroid Tablets, USP contain the labelled amounts of levothyroxine and liothyronine , as established by the USP. The ratio of Armour Thyroid T4 to T3 is 4.22:1 (4.22 parts of T4 to one part of T3).

:We have written on several occasions to the manufacturers to ask for confirmation of their ingredients and for details of their quality control procedures but have received no reply to date.

It is very difficult to believe that Forest Pharmaceuticals have not responded to several written enquiries from BTF. The company has a reputation of being extremely helpful and informative to all enquirers. TPA-UK has written on several occasions to the company and received a response within 24 hours .

You can find confirmation of their ingredients and their quality control procedures on the manufacturer’s web site:

They state that the amount of thyroid hormone present in the thyroid gland may vary from animal to animal, and to ensure that Armour tablets are consistently potent from tablet to tablet and lot to lot, analytical tests are performed on the thyroid powder (raw material) and on the tablets (finished product) to measure actual T4 and T3 activity. Different lots of thyroid powder are mixed together and analysed to achieve the desired ratio of T4 to T3 in each lot of tablets. This method ensures that each strength of Armour will be consistent with the United States Pharmacopoeia (USP) official standards.

Desiccated thyroid extract is not currently licensed in the UK and was withdrawn from use in the UK in the 1970s after synthetic thyroxine had been developed. At that time there was perceived to be a problem with the quality control of thyroid extract with large variations from batch to batch, due to the variation in T4 (thyroxine) and T3 (triiodothyronine) that it contained.

This was NOT due to quality control problems; the suggestion that it was is untrue and there are NO studies to support it. As Armour Thyroid has NEVER been licensed in the UK, it has NEVER been withdrawn. The falling demand was the result of assertions by certain drug manufacturers and medical authorities that the synthetic thyroxine was by definition better, and that porcine thyroid was greatly inferior. There have been NO studies to support this and BTF are seriously in error in making these assertions.

In a 1980 study, a number of generic versions of desiccated thyroid were found to be unreliable in potency. The amounts of T4 and T3 in Armour, on the other hand, were found to be constant (ref 1). Moreover, two-year-old tablets of Armour Thyroid contained similar amounts of T4 and T3 as did fresh tablets.

The following quote from the bible of thyroid treatment, Goodman and Gilmans The Pharmacological Basis of Therapeutics, provides some light on this question. The reason why other brands of desiccated porcine thyroid extract were withdrawn is:

Several years ago (1963), a large batch of material came into the hands of a number of distributors in the United States and Europe and, although of proper iodine content, it later proved not to be thyroid extract at all. This episode gave desiccated thyroid a bad name because several publications about the unreliability of thyroid extract appeared before the hoax was uncovered.

There is concern amongst some doctors over the substantial fluctuations in T3 levels in blood of patients treated with Armour and the potentially harmful effects on the heart (rapid irregular heart beat which predisposes to clots forming inside the heart and then causing strokes) and bones (osteoporosis).

The further allegation that there are substantial fluctuations to T3 levels is once again quite unsupported by evidence. Doctors using natural desiccated thyroid (NDT) have found that over time T3 levels sometimes rise to a small degree without any significant consequence . The assertion that these so-called variations in T3 can cause strokes and osteoporosis is again without foundation or supportive evidence.
We are all aware that over dosage of thyroxine (T4) and tri-iodothyronine (T3) is undesirable, but Armour is no more likely to cause such problems than is synthetic T4 and T3. Splitting the daily dose would obviate any potential concern about transient elevations of T3 levels .

It is difficult to monitor treatment containing a combination of T3/T4 because of peaks and troughs in T3. The long-term effects of T3, Armour, or combinations of T3 and T4 are not known. T3 has a short half-life of a few hours. Patients on T3 have fluctuating T3 levels and at times these may go beyond the upper limit of normal. By contrast T3 levels in patients on thyroxine are stable. Monitoring thyroid hormone replacement in patients on T4 is easy bio chemically because of the stable levels. In someone on T3 or Armour it will depend on the time since the last dose.

The further paragraph concerning monitoring is nonsensical. All thyroxine, whether made by the thyroid itself, or given exogenously, has to be converted to T3; and the thyroid produces just the right combination of T4 and T3 (and T2 and T1) that is available in Armour thyroid. Since T4 and T3 have been released together by the thyroid gland in all mammals (and many other species) throughout evolutionary history, it is absurd to suggest that this combination is potentially damaging. Desiccated thyroid has been used for a century in hypothyroid patients with great benefit and no harm, and the suggestion that the long-term effects are not known are patently incorrect. This is how nature does it and Armour is almost identical to human thyroid.

The BTF sees synthetic thyroxine as the current first-line treatment of hypothyroidism. Current medical practice is governed by evidence. There is no known research showing that porcine thyroid extract is superior to synthetic thyroxine. On the contrary, there are good data that life-long treatment with synthetic thyroxine is safe.

TPA: There is NO known research showing that synthetic thyroxine is superior to natural desiccated thyroid extract. The logic of supplementing a failing thyroid has to be that it is as close to nature as possible; giving T4 alone is not physiological and accounts for the unsatisfactory results in many patients. It is also quite untrue to suggest that blood testing in patients taking Armour is less than satisfactory; indeed, it presents no difficulties of any kind.

The BTF understands that there are concerns about the use of Armour thyroid because of the rapid fluctuations in T3 levels, the difficulties in monitoring such treatment, uncertainties about the long-term health consequences and the considerably higher costs of such treatment. The major professional thyroid organisations and published peer-reviewed guidelines on treatment of hypothyroidism recommend thyroxine as the treatment of choice for hypothyroidism and our position is in keeping with this view.

There may be, at present, no research concerning the increased efficacy of Armour over thyroxine but there is NO evidence to suggest that synthetic T4 is safer. Many patients, who, for various reasons, cannot respond adequately to T4, prefer Armour because it works and actually makes them feel better.

There are now a number of generically manufactured thyroid preparations, and a huge body of patients (not just in UK) complaining of variations in efficacy between different manufacturers. Sadly, many doctors ignore what their patients say in this regard; but the fact is that at the present time, synthetic T4 is actually less reliable in potency than Armour.

Much of the debate about the use of Armour relates to individual accounts of patients who are convinced that switching from thyroxine to Armour has transformed their lives. Doctors are equally aware of patients who have found this treatment unhelpful and some have felt worse than on thyroxine. We feel that it is important to keep an open mind about alternative thyroid hormone replacement regimens to thyroxine, but these issues can only be addressed by a properly conducted prospective randomised controlled trial.

It appears that conventional medicine has not made any serious attempt to evaluate the evidence regarding the empirical use of Armour and that its wholesale dismissal of the concept represents, at least in part, a biased attitude. TPA-UK would like to see the instigation of a properly conducted prospective randomised control trial as soon as possible.

The last paragraph about keeping an open mind is, clearly, the one thing that BTF is not doing. Since natural desiccated porcine thyroid extract was available since 1894, long before synthetic T4, and making patients better, it is up to medical authorities to PROVE on the contrary, that synthetic T4 is as good, safe and reliable as Armour.

I await your comments with interest.

Yours sincerely,
Sheila Turner
Thyroid Patient Advocate

Rees-Jones RW, Rolla AR, Larsen PR. Hormonal content of thyroid replacement preparations. JAMA 1980; 243: 549-550.


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