I would like to clear up some confusion and misconceptions about natural versus synthetic thyroid hormones. The argument from medical doctors that the dosage of thyroid hormone from bottle to bottle is not consistent, is perhaps the most unfounded argument against natural thyroid prescriptions. I have been using Armour thyroid, a natural thyroid hormone, for over 10 years now and have never had a single incident which would make me question this. I have never had a case where a patient reports feeling different after refilling their prescription. Furthermore, I have not seen a significant change to a patient's test results after refilling a prescription at the same dose.
In the last few years I have been using Nature-throid more so than Armour thyroid, for three reasons. The first reason being that Armour thyroid has gone up in price, and more insurance plans are not willing to pay for the medication. Secondly, Nature-throid is available in a larger variety of doses, making it convenient to prescribe a single pill as opposed to two or three pills. I have also learned that RLC Labs the maker of Nature-throid and WP Thyroid ensures no more than a 2% deviation in the dose of their medication suggesting they are ensuring better quality control than Armour thyroid which follows USP guideline which allows for 10% variation form the labeled dose. Just to be clear however, I have never had a problem with Armour.
Nature-throid like Armour thyroid is derived from desiccated pig thyroid glands. Both medications contain a combination of both T3 and T4. I tend to use these medications much more often than Synthroid or its generic form levothyroxine sodium. I do so because I find that more people respond favorably to desiccated thyroid glandular medications than they do to Synthroid or levothyroxine sodium. Unlike many alternative minded doctors, I do not subscribe to the argument that just because one form of medication is natural versus synthetically made, it is automatically better. I do have patients who do better on levothyroxine (synthetic) then they do on the natural thyroid medications. For these patients who do better on on the synthetic form, it is likely that they do not tolerate the immediate effects of the T3 in the natural medications. Furthermore there is a lot of bias against levothyroxine because it is synthetically made. I personally do not buy into this as being a problem as the chemical structure of Synthroid and levothyroxine sodium (T4) is identical to the T4 molecule that the thyroid gland makes with one simple addition of a salt molecule. There is no evidence showing that this slight modification of the hormone creates any problem whatsoever.
To review how thyroid hormone works in a very simplistic way, whether it is from your thyroid gland or from thyroid medication, T4 needs to be converted into T3 to become active. I believe there can be a huge variation within the population for how long it takes for this conversion to occur, as well as how quickly some people metabolize medications in general. For this reason we see differences in how patients tolerate different forms of thyroid medication.
It is important to note that Nature-throid has never undergone a recall of its medications due to mislabeling or problems with manufacturing that would result in a dose that is not consistent with its label. Armour thyroid unfortunately can not make the same claim. In 2010 the FDA issued a recall because some bottles were labeled as 30mg but actually contained 60mg which poses a huge potential risk. It is important to note that these type of recalls are not unique to Armour and occur in the drug industry quite often.
From the FDA website: http://www.fda.gov/Safety/Recalls/EnforcementReports/ucm242808.htm
Armour Thyroid (thyroid tablets, USP), 1/2 grain (30 mg) , each tablet contains 19 mcg levothyroxine (T4) and 4.5 mcg liothyronine (T3), 100-count bottle, NDC 0456-0458-01. Recall # D-231-2011
Lot #: 1077413, Exp. 9/30/2011
Recalling Firm: Forest Pharmaceuticals Inc., Earth City, MO, by telephone and letters on October 6, 2010.
Manufacturer: Forest Pharmaceuticals Inc., Cincinnati, OH. Firm initiated recall is ongoing.
Labeling: Label error on declared strength; some bottles are mislabeled as containing 1/2-grain tablets but actually contain 1-grain tablets. The entire lot is being recalled even though some bottles are labeled correctly because bottles of 1/2-grain and 1-grain could be shrink-wrapped together.
VOLUME OF PRODUCT IN COMMERCE
31,172 bottles approx.
Nationwide, PR, Belgium and the United Kingdom
RECALLS AND FIELD CORRECTIONS: DRUGS - CLASS III
As for levothyroxine, their history of recalls is extensive. I will list some of these with references at the end of this blog post. Just to give you an idea however, between 1991 and 1997 there were at least 9 recalls involving over 100 million tablets. (1) For an in-depth history of levothyroxine and Synthroid read this very detailed history. (2)
Medical doctors who claim that “natural thyroid” is not safe, not regulated or is unreliable, is simply not true. Recalls including those involving Armour Thyroid would have not occurred if the FDA was not involved in the regulation of this medication. Furthermore if your doctor bring any of these points up, ask them if they are aware of all of the recalls for Synthroid and levothyroxine. I find it interesting that many doctors that my patients encounter will claim to know a lot about a medication that they have never used. If you encounter this a patient you may want to find another doctor.
Equally important as the medication is the provider who is making the choices on how to dose the medication. I can't tell you how many times I see patients who are told that once their TSH is brought back into the “normal” range that they are on the right dose, even if their symptom picture did not change at all. Furthermore if you doctor is not re-testing you thyroid levels within two months of prescribing thyroid or at the very least following up with you, find a new doctor to work with. If you are not improving on the medication you are on,your doctor needs to either adjust the dose or consider switching to a different form, regardless of which medication you are on. If however adjusting your thyroid dose and/or medication is not providing symptom relief further work up into the cause of your symptoms should be done.
More links to information regarding recalls:
In May of 2013 there was a recall of Levoxyl (levothryoixine sodium) made by a subsidiary of Pfizer because the potency was diminishing before its stated shelf life.
In 2012, Lloyd Pharmaceutical recalled two levothyroxine sodium products due to inability to maintain their potency. Lloyd Pharmaceutical was selling these products to Forrest Pharmaceuticals.
Synthroid recalls in 2012 and 2013—as the true potency was half that of the labeled dose.
Knoll the original manufacturer of Synthroid class action Lawsuit:
Interesting History of Knoll Pharmaceuticals: