A clinical trial comparing Armour Thyroid (NDT) and Levothyroxine (LT4) is now recruiting patients in the United States.
The sponsor of the study is Allergan, the makers of Armour Thyroid in the United States. They hope to recruit 220 patients at multiple locations listed on the clinical trial website.
In this post, I provide what is known of the study details, and then engage in thyroid science commentary, raising our hopes for the useful, objective scientific insights this trial might reveal.
- Study details
- Inclusion criteria
- Exclusion criteria
- Is an Allergan-sponsored study going to be biased?
- Not a superiority trial, thank goodness.
- The T3-Dominant ratio in desiccated thyroid
- But how will you assess dose conversion?
- Please, TSH is not the ruling judge of safety or efficacy.
- Will the study acknowledge diverse patient response?
- Will they multi-dose?
- High hopes and best wishes
The official name of the study is a mouthful:
A Multicenter, Randomized, Double-blind, Dose-conversion Study to Evaluate the Safety and Efficacy of Hormone Replacement Therapy With Armour® Thyroid Compared to Synthetic T4 (Levothyroxine) in Previously Hypothyroid Participants Who Are Euthyroid on T4 Replacement Therapy
- The Allergan website explains “This study will evaluate the safe and effective dose conversion from synthetic T4 therapy to Armour Thyroid therapy in participants who are euthyroid on a stable dose of synthetic T4.”
- They say ” Oral administration once daily,” which could mean that they will administer doses 1x a day.
- Their primary and secondary outcome measures focus on TSH only.
- Participants who have a diagnosis of primary hypothyroidism made ≥ 12 months before study entry (Visit 1).
- Be on continuous thyroid replacement therapy with synthetic T4 for primary hypothyroidism for at least 12 months immediately prior to the Screening Visit (Visit 1).
- Be on a stable FDA-approved daily dose of synthetic T4 for a minimum of 3 months prior to the Screening Visit (Visit 1). Must enter the study on the same stable dose.
- Have euthyroid status indicated by at least 1 documented TSH value within normal reference range (0.45 4.12 mIU/L, inclusive) at a minimum of 6 weeks and maximum of 12 months prior to the Screening Visit (Visit 1). Also have a confirmed TSH value within the normal reference range drawn at the Screening Visit (Visit 1).
- Male and female participants willing to minimize the risk of inducing pregnancy for the duration of the clinical study and follow-up period (35 days after last dose of study intervention).
- Any clinical condition or previous surgery that might affect the absorption, distribution, biotransformation, or excretion of Armour Thyroid or synthetic T4.
- History of alcohol or other substance abuse within the previous 5 years.
- Known or suspected allergy or intolerance to any ingredients of Armour Thyroid, including its excipients, levothyroxine (T4), other thyroid replacement medications, or pork products.
- Have received active treatment with an investigational drug within 30 days or 5 half lives, whichever is longer, of Screening Visit (Visit 1).
- Current enrollment in an investigational drug or device study or participation in such a study within 60 days of entry into this study.
Since the 1980s, a study of desiccated thyroid has been a very rare event.
The rise of modern clinical trial methodology happened after the era in which most studies of desiccated thyroid therapy were published.
The ONLY “randomized, double-blind” clinical trial comparing LT4 and desiccated thyroid was published in 2013 by Hoang et al. Hoang’s study also titrated doses to the TSH. They found that neither Levothyroxine nor desiccated thyroid were superior to each other. Unfortunately for patients, their abstract hinted that their preference for desiccated thyroid could have been due to feeling happy about some weight loss, a remark that makes light of this benefit and underemphasizes the finding of the equal safety and effectiveness of the pharmaceuticals.
More recently, Tariq et al (2019) did a retrospective study (not a double-blind controlled trial) of desiccated thyroid compared to synthetic T3-T4 combination over an average of 27 months (1 month to 9 years). This study found many clinical benefits of both “natural” and “synthetic” combination therapy at different ratios, while dosing to normalize TSH, FT3, and FT4 at all times. There were NO “risks of atrial fibrillation, cardiovascular disease, or mortality in patients of all ages with hypothyroidism.”
Is an Allergan-sponsored study going to be biased?
Having a drug study sponsored by the drug company that makes it is fairly common in clinical trial practice.
It involves some potential conflict of interest in the study design and the publication of data.
Savovic et al, 2018 has written a concise overview of the issues, saying this:
“Conflicts of interest do not necessarily cause biased trial results, but create the risk thereof.”
The challenge with studies of desiccated thyroid trials has been the opposite sort of bias and conflict of interest: LACK of study.
Proponents of Levothyroxine have refused to engage in clinical trials on desiccated thyroid for decades.
Then they say in guidelines that it’s not recommended because not enough research exists. They thereby openly and shamelessly admit thyroid endocrinologists’ refusal to study it. They make sweeping prohibitions based only on opinion and ignorance — this is anti-scientific pharmaceutical prejudice at its worst.
Imagine if a bunch of rich males decided that they wouldn’t do any medical research on females’ medication needs, basically making things really bad for women who respond differently to medications. What’s wrong with a few rich females funding a study that finally includes females and some meds that might work better for some of them? Oh no, (the biased men will say), they’re biased, and we’re not.
Sex prejudice is taboo, but thyroid pharma prejudice is not yet taboo.
Extremist attitudes are easy to find in segments of the endocrinology community. An infamous anti-desiccated thyroid trial in brazenly declared its bias in its title, “Why does anyone still use desiccated thyroid USP?” (Jackson & Cobb, 1978). Can you hear the sneer? This is the kind of pharmaceutical arrogance and defamation that is permissible among pharma-bigoted physicians, even today, as we hear reports that some doctors are unashamed to voice their vitriolic hatred for this medication to patients who request it.
If desiccated thyroid is so unsafe and ineffective, why was it the gold standard of thyroid therapy long after the mass marketing of levothyroxine began in 1949? Opinions did not shift toward sysnthetic LT4 until the 1970s, and the shift toward levothyroxine was not based on any rigorous clinical trial showing the “superiority” of levothyroxine in terms of long term clinical outcomes. Instead, it was based on medical convenience plus the distaste for T3-dominant biochemistry at a time when people feared isolated transient FT3 elevations without considering the counterweight of a relatively lower FT4.
Therefore, having a trial sponsored by Allergan is far less likely to be discriminatory against desiccated thyroid than if the study was sponsored by the makers or champions of the competing pharmaceutical, synthetic Levothyroxine.
In addition, having a study sponsored by them is better than continuing for another decade only having one double-blind clinical trial attesting the safety and equal efficacy of both LT4 and desiccated thyroid (Hoang et al, 2013).
Not a superiority trial, thank goodness.
Thyroid patients are sick and tired of the litany of synthetic T3-T4 combination trials that have been so poorly designed and which often portrayed as “failure” something quite innocent–the inability to achieve superiority.
Why does one thyroid drug have to be intrinsically superior to another? These are bioidentical hormones, not chemicals foreign to the body.
We all secrete and convert T4 and T3, and one bioidentical hormone is not intrinsically more dangerous than the other when dosed properly.
ALL thyroid medications are capable of being dosed safely and effectively according to an individual’s needs. But NOT ALL patients will respond well to all thyroid pharmaceuticals.
Thyroid pharmaceutical prejudice inevitably results in narrowing the pharmaceutical marketplace, which creates monopolies and harms patients. It is a form of prejudice against patients who only respond well to a less favored thyroid medication or a highly customized ratio of T3 and T4.
Thyroid pharma prejudice can also be anti-synthetic. One should admit that the synthetic thyroid hormone drugs have been carefully engineered to be structurally identical to our own. Enough biochemical study has proven that the human body binds, transports, and converts externally-sourced T3 and T4 molecules in blood the same way as it does internally-sourced thyroid hormone molecules. We even know that the rotation of the molecule’s outer ring is important, and that’s why it’s called Levo-thyroxine not Dextro-thyroxine, which signifies the direction of the rotation. Early studies with synthetics found that the body responds to dextrothyroxine very differently and not as well overall.
So Allergan, thank you, thank you for merely focusing on determining “safe and effective dose conversion” and not making this into a horse race competition.
The T3-Dominant ratio in desiccated thyroid
Here’s another reason why we really need this study.
Far too much anxiety has been spent on worrying that desiccated thyroid does not mimic the “average” healthy thyroid gland secretion ratio of T3 and T4, an average that is found within a wide range of secretion ratios.
Even scientific minds can be duped into thinking that dosing “extra” T3 will lead to “excess” T3, forgetting that dosing only T4 doesn’t necessarily lead to excess T4. Our individualized thyroid hormone metabolism transforms what we dose.
Too many studies have limited “experimental” T3-based thyroid dosing to T3:T4 ratios of 1:14 or 1:16 T3 to T4 micrograms. This is the ratio that is widely yet falsely claimed to be “physiologically correct.” It is not. It is an unnaturally rigid and narrow ratio based on misinterpretation of Pilo’s 1990 kinetic study.
The thyroid gland is a flexible secretor of variable ratios of these two hormones, and the average secretion ratio of T3 and T4 varies widely between individuals, and even daily, within healthy-thyroid individuals (but we lose our daily FT3 fluctuation in LT4 monotherapy).
Even dietary or supplementary iodine supply can shift the T3:T4 secretion ratio.
Besides, FT3:FT4 ratios in blood are far more physiologically significant than ratios in secretion or dosing. A gland’s secretion ratio need NOT be the same as a dosing ratio because the pharmaceutical delivery method is extremely different from natural production.
- Note: In bloodstream, T4 is usually lower in its range than the fluctuating daily average T3 levels in desiccated thyroid therapy. It was not widely understood in the 1970 and 80s, when the most harsh attacks on desiccated thyroid occurred, that more FT3 in blood is metabolically required to compensate for lower FT4. This T3-dominant ratio in bloodstream is not unnatural. It mimics the natural adaptation that occurs in asymptomatic subclinical hypothyroidism when T4 loss triggers a major increase in T3 synthesis and T4-T3 conversion, preventing T3 from falling low prior to therapy. This benignly T3-dominant T3:T4 ratio in blood is something we now understand better thanks to T3 monotherapy studies such as Celi et al in 2010-2011 and Busnardo et al in the 1980s, which examine how higher levels of T3 are necessary to maintain physiological functions in the complete absence of FT4 from bloodstream. Desiccated thyroid therapy results in varying FT3:FT4 ratios depending on the patient.
LT4 monotherapy is certainly not a physiologically correct ratio, because it is devoid of T3, and yet it is safely dosed for many people who convert T4 hormone well enough to achieve their personally euthyroid FT3 and FT4 levels during therapy.
Desiccated thyroid is especially helpful for patients who do not convert T4 hormone efficiently. The medication enables such patients to access Free T3 higher-normal levels and a T3-dominant profile that does not yield thyrotoxicosis. This would not be possible for them on LT4 monotherapy.
Let’s adjust the dosing ratio to the individual, rather than forcing all individuals to adapt to one “magic molar ratio.”
All thyroid therapy is artificial, and what is “abnormal” for people with thyroids can nevertheless be therapeutic for the individual with a disabled, dead or missing thyroid gland.
Hopefully this desiccated thyroid trial will help the thyroid community get over the silly T3-T4 dosing ratio obsessions by showing, once again (after Hoang’s and Tariq’s recent studies), that a 1:4.2 ratio can be as effective as a 1:14 and a 0:100 ratio, depending on the patient’s thyroid disabilities and how you dose it.
But how will you assess dose conversion?
Allergan wishes to examine “the safe and effective dose conversion from synthetic T4 therapy to Armour Thyroid therapy.”
The Armour Thyroid product information pamphlet says “T3 liothyronine is approximately four times as potent as T4 levothyroxine on a microgram for microgram basis”
However, a 4 mcg LT4 to 1 mcg LT3 dosing conversion ratio is highly questionable!
Allergan understands how crucial this is for thyroid therapy. If the dose conversion estimate is way off, many people will be underdosed by replacing too much LT4 with too little desiccated thyroid.
One must do the math and consider that 9 mcg of T3 and 38 mcg of T4 is in 60g of Armour desiccated thyroid when substituting Armour for Synthroid, and realize that the estimate is just a starting point to see what the body will do as it transforms the dose to FT4 and FT3 levels. The math does not have to be perfect, just not way off.
It’s likely that Allergan has been paying attention to trends in thyroid therapy (and likely the frequent occasion of underdose of Armour Thyroid by T3-fearful doctors). They likely had plans in the works for an equivalency / conversion study long ago.
This “pharmaceutical equivalency” per microgram of LT3 and LT4 (and desiccated thyroid) was the topic of two articles that we at Thyroid Patients Canada posted in September, 2019:
- “No, 25 mcg of L-T3 Liothyronine isn’t equivalent to 100 mcg L-T4“
- “L-T3 pharmaceutical equivalency, Part 2: New thyroid science“
In my past articles, I have provided an in-depth historical and scientific critique such claims, showing that the equivalency is closer to 3x rather than 4x, and also that the dosing equivalency ratio of LT4 mcg to LT3 mcg is very individualized.
According to one clinical trial on LT3 vs. LT4 monotherapy, the same target TSH value was achieved at a ratio closer to 3 times the potency, but it varied among individuals (Celi et al, 2010, 2010; Yavuz et al, 2013).
Please, TSH is not the ruling judge of safety or efficacy
Given the contemporary context of TSH-worship, I’m worried by the fact that their primary and secondary outcome measures seem to focus on TSH only.
On their website, not enough detail was provided regarding their proposed methods.
When considering “safe and effective dose conversion,” hopefully the study will measure more than just the TSH response of the patients between LT4 and DTE (desiccated thyroid extract), just as the publications by Celi and Yavuz did that determined a dose equivalency for LT3 and LT4 monotherapies.
Please, Allergan, learn from Celi and Yavuz’s studies.
Celi and Yavuz targeted a TSH from 0.5–1.5 mU/L for their comparison of the two pharmaceuticals, knowing that the vast majority of healthy people have a TSH below 2.5 mU/L and that the TSH population range is way too wide for any healthy-thyroid individual.
They also carefully regulated the patients’ diet during the trial, knowing that calorie restriction lowers TSH by altering leptin signaling in the hypothalamus.
They also measured multiple biomarkers of thyroid hormone action beyond the hypothalamus and pituitary, such as serum glucose, cardiovascular function, body composition, quality of life, exercise test, and other factors.
Yavuz et al, 2013 is the third article that came out of a very rich, detailed study of LT4 and LT3 pharmacokinetics. In that final article, they returned to their idea of targeting a low-normal TSH. They seriously questioned whether the patients were truly “euthyroid” on either medication even when their TSH was lower in reference!
They justly called TSH normalization “Pituitary Euthyroidism” because it a form of euthyroidism that exists at the pituitary alone.
“This modality of treatment [TSH-normalized LT4 monotherapy] is based on the assumption that a state of pituitary euthyroidism (ie, a TSH level within normal range) equates to a state of euthyroidism in all target tissues.”
But Yavuz and colleagues found that this widespread assumption was highly suspect.
When you achieve normal TSH by different ratios of T4 and T3 hormone dosing, you get some very different responses from “target tissues” beyond the hypothalamus and pituitary gland, especially improvement in cholesterol levels and body weight when FT3 is optimized.
“In this context, the data suggest that pituitary euthyroidism, both assessed by basal or TRH-stimulated TSH, does not necessarily equate to a state of generalized euthyroidism at the level of the different targets of the hormonal action. ”
Yavuz and team recommended T3-T4 combination therapy trials and said
“more research must be done to characterize the optimal dosage and the population who may benefit from such intervention.”
Will this study by Allergan do anything to identify not just “optimal dose” but also the optimal “population” for intervention by means of more detailed measurement than just TSH?
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- Will the study acknowledge diverse patient response?
- Will they multi-dose?