Why is the FDA attempting to ban natural desiccated thyroid?
On August 6, 2025, the FDA issued a letter to all manufacturers, importers, and distributors of NDT (natural desiccated thyroid) informing them they would be taking action against them and that doctors have 12 months to transition their patients onto synthetic thyroid hormones. This would effectively ban NDT as a potential treatment option for 1.5 million people who currently rely on it.
If you only have 2 minutes, here are the essential bullet points you need to know.
The Issue:
- FDA issued a letter on August 6, 2025, giving manufacturers/doctors 12 months to transition 1.5 million patients off Natural Desiccated Thyroid (NDT) medications to synthetic alternatives
- NDT is made from dried pig thyroid glands, contains both T3 and T4 hormones, and has been used successfully for over 130 years
- Approximately 10% of hypothyroid patients don't respond well to synthetic T4-only therapy and rely on NDT
FDA's Stated Concerns:
- Claims of inconsistent hormone levels between batches (though clinical data doesn't show this causes significant real-world problems)
- Alleged infection risk from animal tissue (no evidence supports this claim)
- NDT reclassified as a "biological product" in 2022, making it subject to different regulations
The Real Problem:
- George Tidmarsh, acting director of FDA's CBER when the letter was released, is explicitly anti-NDT and working to remove it from market
- AbbVie (maker of Synthroid and Armour Thyroid) petitioned FDA in April 2024 to remove all unapproved NDT brands
- Getting biological product approval costs hundreds of millions of dollars - only big pharma can afford it
- AbbVie appears positioned to monopolize the NDT market if other manufacturers are banned
Current Status:
- Marty Makary posted that FDA is pursuing first approved NDT, but this isn't a formal commitment
- Best case: Only Armour Thyroid survives as a monopoly with higher prices
- Worst case: All NDT becomes unavailable
Actions to Take:
- Sign online petitions supporting NDT access (linked below)
- Contact your congressional representatives about the issue
- Share your NDT success story with FDA Ombudsman (301-796-8530, ombudsman@oc.fda.gov)
- Stay informed as the situation develops (sign up below for updates)
A little over a decade ago, my wife had a total thyroidectomy due to thyroid cancer and has been struggling to recover her health ever since. The first time she was able to do so was after the doctor she was working with helped her transition onto NP Thyroid, a NDT medication currently on the chopping block. I have witnessed firsthand the power of NDT and how for some patients it can be far superior to synthetic alternatives. This move by the FDA will destroy the lives of the 1.5 million people who currently rely on this medication.
Recently, Marty Makary posted on X about this issue, saying that the FDA is committed to pursuing the first-ever FDA-approved NDT medication. Many people on social media are celebrating this as a win and framing it as stopping the ban. I don't think that is the case at all and I don't think the fight is over.
In case you aren't familiar with the medication in question, NDT (natural desiccated thyroid), also known as DTE (desiccated thyroid extract) or ADT (animal-derived thyroid) is a medication used to treat hypothyroidism that is made by drying and finely grinding pig thyroid glands.
It contains the two main thyroid hormones, T3 and T4, in a fixed ratio that reflects the porcine gland. Unlike synthetic drugs levothyroxine (T4) and liothyronine (T3), NDT contains both thyroid hormones and other thyroid constituents naturally present in the thyroid gland. Manufacturers standardize it so each tablet supplies consistent amounts of T4 and T3 according to pharmacopeial specifications. NDT has been used for over 130 years and up until the 1970s was the predominant medication used to treat hypothyroidism.
NDT is currently used by 1.5 million people to treat hypothyroidism. Roughly 5% of the US population has some form of hypothyroidism, and it is estimated that 10% of people with hypothyroidism do not feel better even after starting T4 only therapy and getting their bloodwork to what would be considered normal levels.
Many of these patients turn to NDT medication as an alternative, with great results. This is confirmed in both scientific studies and in a plethora of anecdotal evidence from both patients and doctors who work with NDT as a possible treatment option.
According to the FDA, they have two primary concerns about NDT, from the FDA's website:
- Tablets made from the same manufacturing batches may not always provide the same thyroid hormone levels. Inconsistent doses can have serious consequences for patients. Too much medication can cause unwanted effects, and too little could not be effective.
- Thyroid medications derived from animal thyroid glands have an increased risk of certain impurities due to the source – animal thyroid tissue – or the way it is manufactured. These issues can lead to infections and other health concerns.
In addition to these two concerns, the FDA also says that NDTs are ineligible for pharmacy compounding because they are classified as a biological product. That's an important part of this whole issue and is really what most of the problem hinges on.
First, let's first take a look at the two "concerns" the FDA has with NDT.
We'll start with the second because it's the easiest to address.
There is no evidence whatsoever that NDT comes with any risk of infection. This claim is pulled out of thin air and has absolutely no foundation.
As for the first claim, the higher variability in NDT is real, but clinical data do not support that this routinely leads to significant side effects in practice. Instead, adverse effects most commonly reflect improper dosing regardless of thyroid drug type.
The FDA also mentions it has "received complaints from patients and reports of adverse events related to the safety and potency of these unapproved medications." The FDA receives complaints of adverse events for synthetic thyroid medication as well. No specific complaints or adverse effects are mentioned outside of those already known to be caused by incorrect dosing of either NDT or synthetic thyroid medications.
We do need more research directly comparing NDT to synthetic thyroid hormones, the data is limited. But we also need to acknowledge a key fact that the FDA wants to leave out: NDT has been used successfully for over 130 years and many of the people that take it now have chosen to take it after synthetic options proved ineffective.
This is not the same as a brand new, untested drug with no history.
Marty Makary, FDA Commissioner, stated that the FDA is pursuing the first approved NDT medication. While this represents a potential step in the right direction, we should not be celebrating just yet.
As a quick clarification, medications like NDT being unapproved does not mean they are unregulated by the FDA. They are subject to the same regulations as any other drug. It just means they did not go through the formal approval process because they existed before that process was put in place.
A post on X is not a reversal of or commitment to anything. Let's look at the example of France. NDT was the standard treatment in France up until the 1970s, much like in America, when synthetic options came to market.
French health authorities said they would keep NDTs but required NDT manufactures to resubmit applications for approval, which they were not equipped to do, and NDTs remain off the market in France to this day.
So while Makary's post may be slightly encouraging, it doesn't guarantee patient access to NDTs in the future and reflects the broader issue of whether or not a move like this can be considered to be primarily for "patient safety" when we have over a century and a mountain of anecdotal evidence that these medications are preferred by a large subset of patients.
The FDA is needs to publicly and formally commit to keeping access to NDTs until one is approved, and even that is only a partial victory.
In their letter to manufacturers, the FDA also mentions one of the core issues is that NDTs are classified as a biological product, which is a separate classification of drug. These requirements were recently changed in 2020 so that any medication that includes a protein in the active ingredients is considered a biological product.
The FDA specifically mentions in their guidance (page 5 of the document on that page) that products are only subject to this reclassification if the active ingredient is a protein. The FDA is claiming that because NDT necessarily contains thyroglobulin, which is a protein, it qualifies as a biological product.
But thyroglobulin is not listed as an active ingredient for NDT medication. It acts more as a delivery vehicle. This is a nuanced issue and the way the FDA is classifying this is a strange interpretation of a biologic.
Despite Makary's post, no mention has been made of stopping NDTs from being reclassified as biological products, but why does this matter?
Biological products cost hundreds of millions of dollars and several years to get approved, which means only large pharmaceutical companies can even feasibly accomplish this.
NDT was originally reclassified as a biologic in 2022. While the technical reasons for this reclassification are debatable, NDT manufacturers were originally given until 2029 to comply. So why the sudden acceleration?
George Tidmarsh
George Tidmarsh, who started as acting director of FDA's CBER (Center for Biologics Evaluation and Research) on July 30, 2025, is explicitly anti-NDT. He posted on LinkedIn 8 months prior to his new role that he is "working with the new FDA to remove it permanently from the market".
It's important to understand the goal here. Tidmarsh's stated goal is not to attempt to evaluate the safety or efficacy of NDT. He already has a pre-existing assumption, that they are bad, and is committed to removing them.
For context, CBER is the department primarily in charge of regulating NDT under the new biologic classification. The director is approaching this not with a neutral objective of evaluating them against other options, but with a pre-existing bias against them and a stated goal of removing them from the market.
He claims that they are "proven worse than synthetic thyroid hormone and harmful." I'm not sure what data he's looking at, but I have been unable to find any studies documenting inferior performance of NDT vs synthetic or that they are harmful.
What we do see is some clinical data suggesting that they are equal combined with a mountain of anecdotal evidence that many patients who switch to NDT prefer it over synthetic medications.
In addition to this, there was even stronger indication in that survey that hypothyroidism patients want access to more treatment options overall, not less.
Now here is the really interesting part that raises some questions about the timing of all this. Tidmarsh only held this position for a little over a week. Dr. Vinay Prasad, the former director of CBER, was reinstated on August 11.
The FDA letter went out on August 6. So did Tidmarsh manage to push this through during his 12 day tenure? We already know he was explicitly trying to get NDTs off the market.
In addition to Tidmarsh, there is another player in all this that I think may be partly behind what is going on.
The AbbVie Petition
AbbVie, the company that owns both Synthroid and Armour Thyroid, filed a petition in April 2024 urging the FDA to remove unapproved NDT brands from the market. They listed various reasons in their petition, which we'll dig into in a future post.
But why would AbbVie submit a petition for the FDA to remove NDT from the market when they themselves make one? A major part of their reasoning was that these other companies are unapproved under the biologic classification.
Remember that getting a biological product license can cost hundreds of millions of dollars and take several years. Only very large pharmaceutical companies are capable of actually pulling this off.
AbbVie is likely the only manufacturer that is actually capable of getting this license for NDT.
They are also currently running a very large study comparing Armour to levothyroxine, which they started 3 days after filing the petition with the FDA.
If NDTs are reclassified as a biologic and AbbVie is the only company that is able to legally manufacture it, they will have a monopoly on the market with Armour. Biologics are usually significantly more expensive than traditional drugs, which means many people may be priced out if the price increases.
Pharmacy Compounding
Biological products are also not eligible to be used in pharmacy compounding. Pharmacy compounding involves creating specialized, custom formulations of medications when the off-the-shelf versions do not sufficiently meet patient needs.
Hormone therapy is one of the most common use cases for pharmacy compounding because hormone therapy, such as thyroid hormone replacement, has a very narrow therapeutic window, meaning small changes in dosage can have large impacts.
Pharmacy compounding is a rapidly growing industry, projected to grow from $6.4 billion to nearly $11 billion by 2034, and thyroid medications are a key service they provide.
Why this move on NDT will have such a negative impact
That narrow therapeutic window concept is critical to understand why these events will have such a large impact on thyroid patients.
Despite the big talk about synthetic options being proven to be more effective, we don't know nearly as much as we think we do about the complexity of the thyroid and why some therapies work and some don't.
But what we do currently have are options. For many reasons, some known and some unknown, many patients need a combination of T4 and T3 and NDT in order to function optimally.
My wife for example, tried for 10 years to get rid of her hypothyroid symptoms despite having "normal" levels and finally found success after finding the right combination of Tirosint and NP Thyroid. Nothing else up to that point had worked.
Eliminating options from the market that have been used successfully for over a century doesn't benefit anyone except AbbVie.
So the best case scenario as things currently stand is that we get to keep NDT, but only Armour, with a virtual monopoly, and without the ability to use them in compounding. In the worst case NDTs remain inaccessible and unapproved completely. We really don't know what will happen yet.
I don't know exactly what is going on, but it seems like NDTs are being targeted by the FDA and AbbVie is trying to gain a virtual monopoly on them through some backdoor methods.
Makary's post on X feels more like a pacifying remark than actual progress. If one manufacturer has a monopoly on the entire NDT market due to a questionable reclassification of a widely used drug with no apparent safety issues outside of speculation, can we really call that a win?
So what do we do about it?
There are a few things we can do right now.
Sign Petitions
First, there are several petitions in circulation right now that we can sign.
Contact your members of the House of Representatives and Senators
Go to https://www.congress.gov/members/find-your-member and type in your address to get your representatives' contact information.
Contact their office and tell them that the FDA is targeting a drug that has been safely used for over 130 years and that a major pharmaceutical company is attempting to gain a monopoly on the market, potentially pricing out many individuals from being able to afford life-saving medication.
Familiarize yourself with the issue and use the information here to back up your claim with them.
Contact the FDA
If you are a patient currently using NDT after trying synthetic options, contact the FDA and tell them your story. Inform them that you have already tried synthetic options without success and using NDT was the only thing that made a difference.
You can contact the FDA Ombudsman for this purpose:
301-796-8530
ombudsman@oc.fda.gov
What's next?
I'll be continuing to monitor this situation and will be writing further articles digging into every aspect of this issue. This is a complex, nuanced issue and just because an FDA official made a post on X doesn't mean the fight is over.
My wife, along with millions of other people, have had their lives changed by NDT therapy, and now is the time for us to band together and fight this overreach and regulatory capture.
If you are a patient or doctor that has experienced the benefits of integrating NDT, please reach out to me at kenarogers@proton.me and tell me your story.
I'm in the process of writing a lot more about this issue and the more stories and people we can put together the better chance we will have of getting this decision reversed.