Busting NDT Thyroid Medication Myths: What Doctors Get Wrong

NDT is an acronym for a class of some of the most popular thyroid medications that exist. 

You’ve heard of these medications, even if you don’t know them by this name. 

This class includes medications like Armour Thyroid, NP Thyroid, and the newest, Adthyza. 

By the way, Nature-throid and WP Thyroid are also on this list, but they remain unavailable so we will just ignore them for now. 

Despite being the oldest thyroid medications around, and despite the fact that patients have a clear preference for them compared to synthetic alternatives, doctors remain hesitant to prescribe them. 

That would be okay if they had good reasons, but the truth is, they don’t. 

Which is why today we are going to bust some myths about this class of thyroid medication so when you go into your doctor requesting a medication change, you can walk in with confidence and the knowledge to bat down dubious claims they may make. 

Claim #1: Taking NDT Will Cause Bone Loss & Heart Problems

In my opinion, this is either pure fear-mongering or it reflects an absolute lack of understanding on the part of the doctor making this statement. 

Why is it made?

Because NDT contains a combination of both T4 and T3 thyroid hormones, unlike the synthetic alternatives which only contain T4. 

Doctors know full well that T3 is far more powerful than T4, which is why, when it is given, the dose is much smaller. 

Levothyroxine, for instance, may be dosed at around 100 mcg per day, whereas liothyronine would only be dosed at 5 mcg per day. 

Many doctors are under the false impression that the healthy thyroid gland produces around 95% T4 and 5% T3. 

And since NDT contains a static ratio of around 83% T4 to 17% T3, they assume that it contains more T3 than the average person should take. 

But there’s a big problem with this…

Physiologically speaking, the healthy thyroid gland doesn’t produce a ratio of 95:5 T4:T3, it produces a ratio closer to 80:20 and studies like this prove it (1). 

That covers the T3 issue, which is just false, but what about the heart and bone loss? 

That is also a non-issue because studies have clearly indicated that long-term use of T3 is perfectly safe as long as it is dosed appropriately (2).

So even if you are 80 years old, as long as you’re not taking more than your body needs, you will NOT see an increased risk of osteoporosis or atrial fibrillation just because it contains T3. 

And, yet, this is exactly what many thyroid patients are told. 

Claim #2: Newer Synthetic Medications Are More Effective

Some doctors will claim that synthetic medications like levothyroxine are superior because they contain only T4 which means they are more stable and cause fewer side effects.

They suggest that T3 isn’t needed because the body can simply create T3 from the T4 that is provided in levothyroxine.

This sounds good in theory, but it doesn’t work out this way in the real world. 

We know from studies like this, that patients taking only T4 medications have lower t3 levels compared to those with a healthy thyroid gland (3). 

This indicates that the body does, in fact, require some T3 in addition to T4 which is why it should come as no surprise to hear that the body produces a total of about 30 mcg of T3 each day (4). 

6 of that comes from the thyroid directly and the other comes from thyroid conversion in peripheral tissues. 

What about the side effect claim? 

This claim is true but irrelevant. 

T4 does have a longer life half than T3 so it causes fewer symptoms, but it also leaves patients with residual low thyroid symptoms because it’s so weak.

This is exactly why thyroid patients prefer NDT (5) because it actually helps control their symptoms. 

I think most thyroid patients would be willing to trade off a slightly higher risk of side effects like heart palpitations for more energy, better weight loss, and more hair growth.  

And if you aren’t okay with this trade-off then you can keep taking levothyroxine. 

Claim #3: NDT is Not FDA-Approved

This one is actually true, but again, irrelevant. 

The doctors making this claim are trying to suggest that NDT is somehow harmful because it’s not FDA-approved. 

But the truth is that NDT has been around since 1890 when it was exclusively used to treat thyroid conditions up until the 1970’s. 

The FDA wasn’t even regulating the effectiveness of medications until 1972 and, because NDT was in use for 80 years before this (6), it was grandfathered in. 

Even though it’s been grandfathered in, the FDA still regulates its use and they can very easily pull it off the market if the manufacturers do not follow its rules. 

It just wasn’t required to prove efficacy like newer drugs are because it already has a proven track record. 

So, again, this claim is irrelevant. 

Claim #4: NDT is Old-Fashioned

While it is true that, sometimes, newer versions of things are better than older versions, this isn’t the case with NDT and levothyroxine. 

The reason is there has been no innovation in thyroid medications since NDT was created. 

All thyroid medications contain bioidentical hormones. Every single one. 

That means the same T4 that is found in NDT is also found in levothyroxine. 

And the same T3 that is found in NDT is also found in liothyronine. 

The source is different, but the structure of the compound is identical to what the healthy thyroid gland produces. 

And guess, what?

This is totally fine! 

The only alternative here would be to create a Frankenstein-like thyroid hormone, similar to what oral contraceptives are to progesterone (7), and to use that in place of the bio-identical T4 and T3. 

But there’s no reason to do this as these non-bio-identical versions cause more harm than good and because complete symptomatic control can be achieved by thyroid patients as long as they are dosed correctly. 

In other words, if you aren’t feeling well, it’s probably a dosing problem. 

Claim #5: Taking NDT Will Cause Mad Cow Disease

This claim is ridiculous because, firstly: 

The majority of NDT comes from pigs, not from cows.

And secondly, there’s never been a reported case of mad cow disease from taking NDT ever. 

The only case of mad cow disease in the US came from a cow that was imported from Canada (8), so there’s no cause for concern here. 

Claim #6: Taking NDT Will Increase Thyroid Antibodies

There might be some truth to this one, but it’s probably overblown. 

The idea here is that because NDT comes from an animal source, it almost assuredly contains some animal products that may interact with the human immune system. 

If you’re somebody with autoimmune thyroid disease, like Hashimoto’s, who already has a compromised immune system, then taking natural desiccated thyroid may theoretically make your condition worse. 

In theory, this makes sense, but in the real world, it doesn’t hold up when you look at the numbers. 

We don’t have the exact numbers, but approximately 10-20% of patients with hypothyroidism are taking NDT instead of levothyroxine. 

In real terms, this means about 3-5 million people in the United States. 

We also know that statistically speaking, about 70-90% of people with hypothyroidism have Hashimoto’s. 

So looking at these numbers, we can say with a high degree of certainty that millions of thyroid patients with Hashimoto’s are taking NDT. 

So do we see millions of cases of elevated antibodies in these people? 

Nope, not even close. 

But I can tell you from experience that I have seen at least one person react in this way so it is a rare but possible interaction. 

But, in my opinion, not enough to make the claim that NDT should be avoided. 

Claim #7: NDT Isn’t A Real Medication Because it Can Be Purchased Over The Counter

This one stems from a serious misunderstanding of the difference between over-the-counter supplements known as thyroid glandulars and NDT which is a prescription medication. 

Thyroid glandulars are bovine-based over-the-counter ingredients that usually do not contain thyroid hormones but can in some situations. 

NDT, on the other hand, is a prescription thyroid medication that is only available from your doctor and contains standardized amounts of T4 and T3. 

They are not the same thing, they come from completely different sources, and they contain completely different ingredients. 

But of course, if someone isn’t educated, they may confuse them. 

All of this said, should you run out and switch from whatever you are taking to a form of NDT? 

Not necessarily because it’s definitely possible to feel good on the synthetic medications as well. 

But if you are someone who is struggling to feel better on whatever you’re taking then I would recommend reading this article next. 

It walks you through the steps needed to make sure you can optimize your thyroid medication to feel your best.