Tag: T4 | Page 2 | Dr. Westin Childs: Thyroid Supplements & Thyroid Resources
synthroid overdose: signs you are taking too much thyroid medication

Synthroid Overdose: Signs & Symptoms You’re Taking too Much

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Are you concerned that your dose of Synthroid is too high? That may be the case, especially if you are experiencing symptoms such as hair loss, heart palpitations, and heat intolerance.  The good news is that Synthroid overdose can be easily treated by simply reducing your dose.  This article will outline the major side effects …

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is synthroid gluten free?

Is Synthroid Gluten-Free?

Are you actively trying to avoid gluten-containing foods? Do you also have hypothyroidism? If so, then this article is perfect for you.  I’m going to jump the gun and tell you that Synthroid is indeed gluten-free, but it may contain other ingredients that can cause issues.  We are going to discuss the gluten content of …

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Thyroid Deiodinase How D1, D2 & D3 Enzymes Alter Your Thyroid

Thyroid Deiodinase: How D1, D2 & D3 Enzymes Alter Your Thyroid

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Thyroid deiodinase enzymes serve to manage thyroid hormones at every level of metabolism.  Even more important is the fact that these enzymes can become dysregulated by everyday common medical conditions.  Understanding the importance of these enzymes is critical to understanding how to further treatment, especially if you are taking thyroid medication such as levothyroxine or …

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High TSH normal T4: What does it mean?

High TSH & Normal T4: What Does it Mean? + Other Thyroid Lab Patterns

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Are you experiencing a high TSH but normal T4? Are you confused about interpreting these values? Is your Doctor telling you that your tests are normal even though you are experiencing abnormal symptoms? This article will help shed light on this thyroid lab pattern and help you understand what it means.  You’ll learn more about …

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Is Natural Desiccated Thyroid (NDT) the Best Thyroid Medication?

Is Natural Desiccated Thyroid (NDT) the Best Thyroid Medication?

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Natural desiccated thyroid is a thyroid medication that comes from pigs!

This medication contains a more “complete” profile of thyroid hormones when compared to almost all synthetic thyroid medications out there. 

This has led many people to tout NDT as the “best” thyroid medication. 

In this article, we are going to explore this claim while also discussing the pros and cons of this medication. 

You’ll learn who should use this medication, who should avoid it, and the pitfalls of using it

Let’s dive in: 

What is NDT or Natural Desiccated Thyroid Hormone?

NDT or natural desiccated thyroid hormone is simply a type of thyroid hormone medication. 

It can be used to treat people who have low levels of thyroid hormone in their body from conditions like Hypothyroidism and Hashimoto’s thyroiditis. 

NDT is often claimed to be one of the “best” thyroid medications out there because it’s considered to be all-natural. 

So, with this in mind, let’s break apart what NDT actually is. 


Where does NDT come from?

NDT is porcine-derived which means that it comes from pigs. (1) 

To get NDT, people must take the thyroid gland of pigs and desiccate or dry it out. 

From there it is standardized to a specific dose and contains 38mcg of T4 (the inactive thyroid hormone) and 9mcg of T3 (the active thyroid hormone) in each grain. 

Grain is just a way to standardize the dose of NDT between different brands. 

Natural desiccated thyroid also contains other hormones and prohormones such as other types of thyroid hormone (T1 and T2).

These hormones are not nearly as active as T4 and T3 but they are thought to play an important physiologic role in the body otherwise, (2) why would your body produce them?

Each grain of NDT contains around 76% T4 and around 23% T3 which is a ratio close to the 80% T4 and 20% T3 that your thyroid produces naturally when it is healthy. 

For this reason, and because it contains prohormones, and because it comes from a natural source, (3) many people believe it is one of the most complete thyroid medications out there! 

While this may be true, it doesn’t mean that it works equally well for every single person. 

Let’s dig into the basics of NDT and talk about why it may not be the best medication. 


Foods to Avoid if you Have Thyroid Problems:

I’ve found that these 10 foods cause the most problems for thyroid patients. Learn which foods you should avoid if you have thyroid disease of any type.


The Complete List of Thyroid Lab tests:

The list includes optimal ranges, normal ranges, and the complete list of tests you need to diagnose and manage thyroid disease correctly!


Natural vs Synthetic Hormones

NDT is considered to be natural because it is sourced from a “natural” source, pigs. 

This sourcing of thyroid hormone is different from the approach used to create other formulations of medications such as Levothyroxine and Synthroid

Other medications are created in a laboratory from other basic compounds. (4) 

But you must always remember that ALL types of thyroid medications are considered to be bio-identical which is very important. 

Bio-identical means that the hormones you are taking by mouth are considered to be IDENTICAL to the hormones that your body produces naturally!

Where these medications differ is in the SOURCE. 

The source for NDT is from pigs while the source for Levo and Synthroid is other chemical structures. 

Some people believe that naturally sourcing thyroid hormone is superior to creating it chemically in a lab. 

From my perspective, there is no difference between thyroid hormone from a human or a pig when compared to thyroid hormone created in a lab

Both compounds look the exact same and function in a similar way in the body. 

Where they differ is in the other hormones and pro-hormones that come in NDT formulations. 

NDT Brands

Let’s take a second to discuss the various brands of natural desiccated thyroid hormones out there. 

There are several “well-known” brands and some less well-known brands. 

What you need to understand is that these medications do differ in the type of active and inactive ingredients in them but they all contain both T4 and T3 thyroid hormones. 

While it may not sound like the inactive ingredients make a big difference, they actually may be the reason that some people simply can’t tolerate certain types of NDT brands. 

For instance:

It’s not uncommon for someone to be on Armour thyroid but not feel well when switching to Nature-throid or WP thyroid even if their dose stays the same. 

These differences are likely the result of how your body interacts with the inactive ingredients and how difficult it is for your intestines to break down and absorb the hormones in the medication. 

What that means for you is that if you don’t tolerate one type of NDT brand it doesn’t mean you won’t tolerate all of them. 

Instead, you may want to switch to a couple of different brands to see if you can find one that works for you. 

With that in mind you can find a list of NDT brands below: 

Is NDT Superior to T4 Medication for Hypothyroidism?

It is largely felt by many online communities that natural desiccated thyroid is the single “best” thyroid medication out there. 

This logic has led people to believe that if you are taking NDT and it isn’t working for you that the problem must be with your dose and not with the medication itself. 

I’m not a fan of this approach and don’t believe that when it comes to your thyroid that there is a single “best” thyroid medication

A better approach is to always listen to your body while you look at other problems beyond your thyroid

Thyroid tunnel vision can lead you to believe that every problem you have is associated with your thyroid and that adjusting your dose is the solution to this problem. 

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This approach to management has led many patients to take higher than necessary doses of thyroid medication which can be dangerous! 

So, while NDT is a great medication, it’s certainly not the “best” or the only thyroid medication available. 

The type of thyroid medication that you use, and your dose, should be individualized to YOUR body. 

Natural Desiccated Thyroid for Weight Loss

One important note worth mentioning is that of weight loss and NDT. 

Some studies, like this one, have shown that switching to NDT does result in modest weight loss in certain patients. (5) 

This particular study took a look at 70 patients that were already taking T4 medication (Levothyroxine). 

This group of patients was taking this medication and despite having a normal TSH still had some symptoms of hypothyroidism. 

Thyroid lab tests in patients taking natural desiccated thyroid compared to T4

These patients were then randomized and given NDT (desiccated thyroid extract) for 16 weeks and then placed back on their old medication. 

During the period that these patients were taking NDT, they noticed around a 3-pound weight loss on average and roughly 50% of patients taking NDT wanted to stay on it. 

Not only did they lose weight but they also reported feeling much better on the medication in a subjective sense (based on their own opinion). 

3-4 pounds may not sound like a big deal to you, but when you realize that weight is incredibly difficult to lose when you have hypothyroidism this is actually a great feat. 

But does this mean that the weight loss is due to NDT itself or simply due to the T3 in the medication?

While we don’t have definitive studies, it’s logical to believe that the same results would have been achieved by simply adding T3 (in the form of Cytomel or Liothyronine) to existing doses of T4 in these patients. 

So, while NDT can certainly help you lose weight if you have hypothyroidism, don’t fall into the trap of believing that the weight loss is caused by the NDT itself. 

Instead, the weight loss is most likely the result of IMPROVING the total T3 and free T3 levels in your body! 

And this can be done with T3 medication of any type. (6) 

Common Problems and Symptoms when using NDT

Let’s talk about some of the problems associated with NDT use. 

The way that your body responds to NDT is going to be different from other people out there. 

This means that the type of NDT that you use, and the dose that you use, all may potentially lead to problems. 

What’s important is to focus on how YOU feel and how YOU tolerate the medication. 

By listening to your body, and by checking your thyroid lab tests, you can be certain that you are taking the right dose for your body. 

You can find a list of the most common problems that patients experience when they use NDT below: 

  • Some people take too much natural desiccated thyroid hormone – (7) Overdosing on NDT is a common problem because many people believe that higher doses will somehow improve their thyroid function. This leads to overdosing and symptoms of hyperthyroidism in some patients. This problem stems from “thyroid tunnel vision”.
  • Dosing is static which means you can’t tweak the T4 and T3 concentrations – NDT comes in a static dose of 38mcg:9mcg of T3. This means that you can’t individually adjust the amount of T3 in the medication without also adjusting the T4. You might do great on 38mcg of T4 but may need something like 5mcg of T3. If you fall into this category then you can’t adjust your medication. 
  • May lead to variations in free T3 & Free T4 levels – Some people experience very high free T3 levels and very low free T4 levels even when using low doses of NDT. This problem probably has to do with how each individual processes thyroid hormone in their body. 
  • Symptoms arise from the use of T3 which can be difficult to manage in some patients – (8) Some patients are exquisitely sensitive to even incredibly low doses of T3. These are patients that would probably do fine on certain types of T4 medication (such as Tirosint) but do poorly when they start even low doses of NDT. 
  • May be hard to break down for some patients in the intestines – This problem isn’t unique to NDT medications, but it’s worth considering if you have intestinal issues. Inactive dyes and fillers may cause reactions and may make the digestion of NDT difficult. 
  • May lead to immunogenic reaction (may not be ideal for patients with Hashimoto’s) (9) – There is a theoretical risk that taking a foreign pig-derived substance can “flare” up the immune system and worsen thyroid function in patients with Hashimoto’s thyroiditis. I don’t think this is a reason to completely avoid NDT if you have Hashimoto’s thyroiditis but you should be aware that it can happen.

Overdosing on NDT

Believe it or not but doctors have been using NDT since the 1950s!

Even back then it wasn’t uncommon for doctors to prescribe high doses of NDT (up to 3 to 8 grains per day) to patients. (10)

This was way before thyroid lab tests were created, so dosing was often based on the “Basal metabolic rate” which is a marker for metabolism. 

These doctors found that increasing the dose of NDT did result in modest weight loss by increasing the metabolism, but once the dose was lowered, the metabolism of the patient went back down to below-normal levels. 

This is as relevant today as it was back then. 

Currently, many people believe that by simply increasing their dose of NDT that they will finally feel better and relieve their symptoms. 

This happens frequently in patients who are suffering from weight gain. 

This leads to higher and higher doses of NDT which dramatically suppresses the TSH and temporarily helps with weight loss. 

But the unintended effect is that it may also cause long-term harm because of the high dose of NDT being used. 

Studies dating back to the 1950s showed that if you are responsive to NDT you only need a small dose (usually 1-2 grains) to improve your symptoms and improve your metabolism. (11) 

If you are still feeling symptomatic at that point then some of your symptoms are likely related to some other problem or some other hormone imbalance!

You can avoid these potential negative side effects by using only the appropriate dose and by monitoring your thyroid lab tests in the process. 

Who should use NDT

NDT is a great medication and many people out there stand to benefit from its use. 

I’ve compiled a list of just some of the patients that tend to do the “best” on this medication below: 

  • Those who have failed T4 medication – If you’ve been on T4 medication such as Levothyroxine or Synthroid and you just aren’t feeling well after 6-8 weeks then it may be time to consider a T4/T3 combo medication. 
  • Those with low free T3 levels (usually need a T3 medication) – Up to 15% of the population suffers from thyroid conversion issues which means they don’t convert T4 into T3 as well as other people. If you fall into this category you may have a “normal TSH” but your free T3 and total T3 levels may be lower than normal. If you fall into this category then adding T3 (from either NDT or Liothyronine) may help bring these levels up and help you feel better. 
  • Those who are post-thyroidectomy – Your thyroid (when functioning normally) produces around 80% T4 and around 20% T3. If you don’t have a thyroid, because it was removed or destroyed, then it makes sense to supplement with thyroid hormones close to this ratio. Most post-thyroidectomy patients take only T4 medications (so 100% T4) which do not contain T3. Some of these patients don’t feel well despite having a normal TSH. Taking NDT can provide your body with T3 in a ratio that is close to what your body produces naturally and may help those without a thyroid. (12)

This is not an all-inclusive list but it can help get you started! 


Natural desiccated thyroid is a thyroid medication that contains both T4 and T3. 

Because of this, it may be one of the better thyroid medications (but not the best!) out there. 

If you have thyroid issues and are struggling with low free T3 levels, weight gain, and/or other symptoms despite having a normal TSH, then this medication may help you

When using it be careful to watch for side effects such as anxiety, heart palpitations, or hot flashes which may indicate that your dose is too high. 

Now I want to hear from you:

Are you taking NDT? Is it working for you?

Are you not tolerating NDT?

Is it causing negative symptoms?

If so, leave your comments or questions below!

I’ll do my best to respond to each comment. 

#1. https://www.ncbi.nlm.nih.gov/pubmed/10365676

#2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4272398/

#3. https://www.ncbi.nlm.nih.gov/pubmed/15253676

#4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4146262/

#5. https://www.ncbi.nlm.nih.gov/pubmed/23539727

#6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5965938/

#7. https://www.ncbi.nlm.nih.gov/pubmed/29942726

#8. https://www.sciencedirect.com/science/article/pii/B9780323189071000883

#9. https://www.ncbi.nlm.nih.gov/pubmed/9545109

#10. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1642898/?page=1

#11. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4980994/

#12. https://www.ncbi.nlm.nih.gov/pubmed/23072197

NDT thyroid medication vs other thyroid medications
T4 to T3 conversion_ factors that decrease thyroid function

T4 to T3 Conversion: Factors That Decrease Thyroid Function

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YouTube video

This is lesson #5 in the thyroid beginner series. 

As you know, this series is designed to help you understand the most basic concepts about thyroid function so you can be a better advocate for your own health

Today is all about T4 to T3 conversion. 

This is the process by which your body creates and activates thyroid hormone. 

It’s important because there are steps that you can take to actively enhance this conversion process and help reduce (or improve) your symptoms. 

Let’s jump in: 

T4 to T3 Conversion Explained in Plain English

This is really a continuation of the concepts that were built upon in lesson #3 and lesson #4 which discuss T4 and T3 thyroid hormones. 

They are short videos (less than 10 minutes each) so if you don’t feel like you have an understanding of thyroid hormones then go watch those before you jump into this lesson. 

As I stated previously, T4 to T3 conversion is the process by which your body takes inactive thyroid hormone and activates it (1).

This process is also known as thyroid conversion or peripheral thyroid conversion but don’t let this confuse you because they are all referring to the same process. 

In this conversion process, your body takes T4 thyroid hormone, which it either produces on its own or that you’ve taken by mouth, and cleaves off a portion of the molecule which changes its shape and structure. 

This change alters the hormone to T3 (triiodothyronine) which is the active thyroid hormone. 

Why is this important?

Because the more T3 you have in your body the better your thyroid functions

The less T3 you have in your body the more symptoms you will experience

What that means for you is that you want this process to be working at 100% because if it isn’t then you will be producing less active thyroid hormone. 

It turns out that the way that your body increases or decreases this conversion process is through the activity of special enzymes

These enzymes, known as deiodinase, are responsible for “cleaving” off an iodine moiety on the T4 hormone. 

T4 is named T4 because it contains 4 iodine portions on the hormone base. 

Once it loses an iodine portion it now only has 3 and we call it T3. 

Approximately 80% of the T3 in your body is created through this conversion process which means it’s very important for thyroid health. 

This conversion process matters if you have a thyroid, if you don’t have a thyroid, if you have Hashimoto’s, if you have thyroid nodules, if you have thyroid cancer, and so on. 

Basically, it matters for everyone.


Because even if your thyroid isn’t working you still have to take thyroid hormone by mouth and most thyroid medications contain T4 (not T3). 


Foods to Avoid if you Have Thyroid Problems:

I’ve found that these 10 foods cause the most problems for thyroid patients. Learn which foods you should avoid if you have thyroid disease of any type.


The Complete List of Thyroid Lab tests:

The list includes optimal ranges, normal ranges, and the complete list of tests you need to diagnose and manage thyroid disease correctly!


Factors that DECREASE T4 to T3 Conversion (These slow down thyroid function)

There are certain factors that can slow down the conversion of T4 to T3 by interfering with the efficiency of the enzymes responsible for this conversion.

These factors act as a brake on your entire thyroid system. 

They slow down the amount of T3 that your body is able to produce and may make less efficient the medication that you are taking.  

If you can address and reverse these issues then you can “release” the brake on your thyroid and finally start feeling better! 

I’ve created a list of the most common factors that blunt this conversion process below: 

  • Dieting & Calorie restriction (slows down your metabolism) – Calorie restriction, as little as 1,500 calories per day for 3 weeks, is enough to blunt thyroid function and reduce T4 to T3 conversion (2). This might be the #1 problem for many thyroid patients who also tend to struggle with weight. They get trapped in a situation where they are overweight but try to diet to reduce the weight, only to further reduce thyroid function which leads to weight gain
  • Inflammation (from any cause) (3) – Inflammation is really nonspecific but inflammation from any cause (if systemic) can damage thyroid function. You can identify inflammation by looking for markers such as CRP and ESR. If elevated, these markers may be an early sign of inflammation. 
  • Lack of sleep (4) – If you are sleeping less than 8 hours per night then you may be reducing your thyroid function without realizing it
  • Intestinal issues (Dysbiosis, IBS/IBD, etc.) – A large portion of thyroid conversion actually happens in the GI tract or gut (5). If you have problems in the gut then this may limit your ability to convert T4 to T3. Problems such as intestinal dysbiosis (changes in gut bacteria), inflammatory conditions such as SIBO/SIFO/IBD, and other issues can all cause issues. Treating gut-related issues should be a priority if you have thyroid disease. 
  • Stress (emotional, physical, etc.) – Stress, from any cause, will limit thyroid function and block thyroid conversion (6).
  • Chronic and acute infections – Acute infections such as pneumonia can cause issues but also more chronic infections such as viral or bacterial overgrowth syndromes can also cause issues. 
  • Medications – It is well known that certain prescription medications can block thyroid function (7). Included on this list are blood pressure medications, diabetic medications, seizure medications, iodine, PTU/Methimazole, steroids, and heart medications like amiodarone. It may not be possible for you to stop taking your medication but you should look for alternatives if possible. 
  • Endocrine-disrupting chemicals (those you come into contact with daily, some people are more sensitive than others) – Endocrine-disrupting chemicals are chemical compounds that humans come into contact with on a daily basis that look like real hormones but aren’t. These hormones can trick your body into thinking the real hormones are there and they may compete for binding on cellular receptors (8). EDCs are found in plastic bottles, receipts, foods, plastics, and many other items that you come into contact with daily. Limiting your exposure to these chemicals may help improve your thyroid function. 

If you have any of these issues going on in your body then your thyroid function may suffer. 

These conditions may lead to an increase in a metabolite known as reverse T3 (a topic for another time). 

Reverse T3 is the metabolite created when your body is having trouble with the thyroid conversion process. 

Therefore, it can be used as a marker of thyroid conversion in your body. 

You can test for reverse T3 with a simple blood test. 

Factors that INCREASE T4 to T3 Conversion (You can use these to improve how well your thyroid works)

So what are you supposed to do if you have any of the factors listed above?

This section will discuss some of the available therapies that you can use to potentially help improve T4 to T3 conversion. 

  • Fixing the problems listed above (you must know what is causing the issue!) – The first, and most important, option is to try and find the root cause of your issue and address that problem. This may require a physician to help but in many cases, it will not. For instance: if you know you are struggling with calorie restriction then the first step is to stop that behavior! If you have known gastrointestinal issues then you can address that problem with basic therapies such as probiotics or enzymes. If you are struggling with stress then adding yoga or meditation to your daily regimen can help. If you are having issues with sleep then you can focus on ways to improve that and so on. Some issues, such as the use of medications, may require that you find a physician to help (and even then you may not be able to adjust your medications). In many situations, you may find that you have a number of factors that are limiting your T4 to T3 conversion. Each of these factors may contribute 5-10% so you may have to address many issues to see noticeable improvement. 
  • The use of certain supplements – Another strategy to improve T4 to T3 conversion is to use certain supplements. Supplements such as zinc, selenium (9), and guggul may all help your body naturally improve this process. The use of minerals such as zinc and selenium will only help if you are deficient, but many people around the world most likely are due to poor widespread dietary patterns. I’ve included the most effective mix of nutrients and vitamins in my T3 conversion booster which has helped many people improve thyroid function. You can learn more about that supplement here
  • Exercise (the right amount for your body) – Exercise is one of the easiest ways to increase both T4 and T3. A moderate amount of exercise can improve thyroid hormone production from your thyroid gland while simultaneously increasing thyroid hormone levels. The only catch here is that you must be exercising enough while avoiding overexercising. Overexercising can actually cause the opposite effect and lead to decreased levels of both T4 and T3. Learn how much is enough in this guide
  • Diet – While your diet doesn’t directly influence thyroid conversion it can absolutely indirectly affect thyroid conversion. Consuming unhealthy foods can lead to things like low-grade inflammation and gut problems. Both of these variables can negatively impact thyroid conversion. Learn which foods to avoid and which foods you should be eating to promote healthy thyroid function in this guide
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Using these strategies can help you increase thyroid function naturally and may even help if you are taking medication. 


If you are taking thyroid medication your body still must convert T4 into T3. 

So all of these factors still matter if you are taking thyroid medication or if you don’t have a thyroid at all. 

The good news is that almost everyone with thyroid-related issues can benefit from this information. 

Bypassing T4 to T3 Conversion with T3 Medication

Another strategy that we will discuss (briefly) is the use of T3 thyroid hormone to bypass T4 to T3 conversion. 

We already discussed the importance of T3 and how it does pretty much all of the heavy lifting when it comes to thyroid function in your body. 

Normally, thyroid medications that contain T4 must be activated to T3 before your body can really use them

But you can skip out on this process by using T3 medications such as liothyronine or Cytomel

If you ingest T3 medications then they do NOT require activation in the way that T4 medications do. 

This allows you to bypass the conversion process and start feeling better almost immediately. 

This doesn’t mean that you should skip out on all of the therapies listed above, but instead, combine them all together for maximum benefit. 

I find that using medications that contain T4 + T3, using supplements designed to improve thyroid conversion, and addressing issues that blunt thyroid function all at the same time cause the best results clinically. 

You can learn more about using T3 medications here


The bottom line?

Addressing this tiny concept known as thyroid conversion may be one of the most important things that you learn about your thyroid. 

Most of the time, patients feel helpless with their thyroid because so much depends on their doctor and what he/she is willing to do. 

But if you understand your thyroid you can take steps to optimize whatever thyroid function your body is capable of producing

Just remember:

This is a process and it takes time!

Don’t expect immediate results, but instead, give your body weeks to months to improve. 

Now I want to hear from you:

Are you struggling with T4 to T3 conversion? 

Have you tried therapies designed to improve this process?

Have they worked for you? Why or why not?

Have you tried T3 medications?

Leave your comments and questions below! 

Scientific References

#1. https://www.ncbi.nlm.nih.gov/pubmed/6479377

#2. https://www.ncbi.nlm.nih.gov/pubmed/1249190

#3. https://www.ncbi.nlm.nih.gov/pubmed/27051079

#4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2910542/

#5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1411539/

#6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3148770/

#7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1070767/

#8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5751186/

#9. https://www.ncbi.nlm.nih.gov/pubmed/25758370

how to increase T4 to T3 conversion
T3 basics the test, the medication, the hormone

T3 Thyroid Hormone: What Your Doctor Isn’t Telling You

This is lesson #4 in my thyroid beginner series and today it’s all about the hormone T3.

The last lesson we discussed the value of T4, how it is produced, what it does, and how it influences your body. 

We’re going to do the same thing in this lesson but discuss the other (more active) thyroid hormone: 


Foods to Avoid if you Have Thyroid Problems:

I’ve found that these 10 foods cause the most problems for thyroid patients. Learn which foods you should avoid if you have thyroid disease of any type.


The Complete List of Thyroid Lab tests:

The list includes optimal ranges, normal ranges, and the complete list of tests you need to diagnose and manage thyroid disease correctly!


What is T3?

T3 is the most powerful thyroid hormone that your body produces. 

If you were paying attention yesterday then you know that your thyroid gland, under the influence of TSH, produces T3 thyroid hormone directly. 

In fact, about 20% of the total amount of hormone that your thyroid produces is T3 (1).

This hormone influences almost every cell in your body, through nuclear receptors, and can be tested through routine blood work. 

Your doctor can also prescribe T3 as a medication directly. 

Later in this video and post, we will talk about why many people may actually need T3 medication to feel optimal. 

But let’s focus on T3 as a hormone first. 

T3 as a Hormone

T3 is often referred to as triiodothyronine, especially on lab work or in scientific studies. 

But don’t let this confuse you, because triiodothyronine is another name for T3 and both are referencing the same active thyroid hormone. 

You know that T3 is the most active thyroid hormone in your body, but how does your body get the hormone?

Through 2 main ways:

#1. Your thyroid gland produces it directly (20% or so)

#2. And through the conversion of T4 into T3 (2).

T3 then circulates through your body where it impacts nearly every cell, either on the surface of the cell or directly in the nucleus (3), to cause all of the positive benefits of thyroid hormone. 

T3 is responsible for helping your hair to grow, providing you with energy, helping you lose weight, lifting your mood, increasing your heart rate, managing your cholesterol, and so on. 

All of these benefits come from the effects of T3 on the cell. 

How do you end up with low T3?

Well, if we go back to the two main ways that we know your body produces T3 we can reverse engineer what can cause low T3. 

#1. Your thyroid gland isn’t producing ENOUGH of it.

Conditions such as hypothyroidism, Hashimoto’s thyroiditis, inflammation of the thyroid gland and obesity can all result in reduced production of thyroid hormone directly from your thyroid gland. 

A reduction in either T4 or T3 will lead to low T3 in your body. 


Because of reason #2:

#2. And/or you aren’t able to convert T4 into T3 adequately. 

The thyroid conversion is the process by which your body takes circulating T4 and turns it into T3, through certain enzymes (4), when it needs to. 

If you have a low supply or reservoir of T4 then obviously the amount of T4 that your body can draw upon to create T3 is limited and this may lead to low T3 in your serum (that you can test with lab work). 

If you can identify which issue is causing low T3 in your body then you can help direct your therapy and treatments. 

But just realize that regardless of the reason, if you have low T3 you will likely experience the symptoms of hypothyroidism. 

T3 as a Lab Test

T3 can be easily tested in the blood through two main tests:

#1. Free T3 (amount of unbound active thyroid hormone)

#2. And Total T3 (total amount of T3 in the serum)

Testing for T3 gives you an idea of how much function your thyroid gland has on your body because you are testing for the active thyroid hormone (compare this to T4 which is less biologically active (5)).

T3 is therefore probably the single most important thyroid test that exists (superior to even TSH) (6).

With this in mind, you will want to put a priority on your T3 and ensure that it is in the “optimal” range. 

You can use the example below to illustrate the point: 


In this example, the free T3 is measured at 2.3 with the reference range of 1.7 to 3.7. 

So, from a technical standpoint, the lab is measured in the “normal” range and this is probably what most physicians would tell you. 

But what they fail to realize is that most of your hormones operate on a spectrum ranging from zero function to optimal function and everything in between. 

You can still “function” with a sub-optimal T3 but you may pay the price of fatigue, hair loss, constipation, and weight gain as a result. 

It’s in your best interest, then, to ensure that it is “optimal” for your age. 

You do not want to compare your personal T3 to that of someone in their 80’s or 90’s, instead, you want to compare it to a healthy person that is age-matched to you (currently labs are not set up to give this information) (7).

The “optimal” value will vary from person to person but a safe assumption is that you want your free T3 value in the upper 50% of the reference range that you are given (reference ranges change based on the lab). 

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In a perfect world, you would have tested your free T3 when you were “healthy” and have that as a comparison, but that’s incredibly rare. 

So, without this knowledge, you can assume that a healthy range is probably near the top of the range. 

In our example that would mean that the “optimal range” would be anything greater than 2.7 putting this patient at a slightly sub-optimal level. 

Another important point to mention is that your T3 should always increase if you are taking any type of thyroid medication. 

If your T3 doesn’t increase with medication then you need to take a look at conversion, absorption, or look into using a different type of thyroid medication

T3 as a Medication

T3 can also be used as a medication either by itself or in combination with T4 (and other thyroid medications). 

We’ll get into the various formulations of T3 below.

T3, because it is so powerful, tends to have more side effects when compared to T4. 

This doesn’t necessarily mean that you should avoid T3 medication but it does mean that it’s more difficult to dose correctly and this may be part of the reason that Doctors shy away from using it. 

T3 has a direct influence on your heart cells which can cause your blood pressure and heart rate to increase immediately after taking the medication. 

You may feel this sensation as heart palpitations and/or anxiety. 

These types of symptoms usually go away over time or as you adjust your dose and aren’t necessarily a reason to stop using the medication. 

It’s also important to realize that T3, like thyroid medication, is probably the most effective medication for helping with weight loss (8).

If you are struggling with weight loss, and you have thyroid disease, you need to take a close look at your Free and Total T3 levels (see examples above). 

Liothyronine & Cytomel

Liothyronine and Cytomel would be considered “immediate release” versions of T3 because they are usually rapidly absorbed into the body after ingestion. 

And because T3 has a short half-life, it’s not circulating around in your blood for a significant amount of time (9).

This may be an issue for some people who then opt to take more frequent, but smaller, doses throughout the day. 

This problem is largely solved with SR T3. 


SR T3 is a compounded medication in which the active T3 hormone is bound to a “sticky” material which delays or slows down the absorption of T3 in your intestinal tract. 

This allows for a slow but steady stream of T3 into your body throughout the day. 

SR T3 is often preferred if you experience symptoms such as heart palpitations, anxiety, or headaches when using T3. 

One potential problem with SR T3 is that it may dramatically reduce the absorption of the dose that you take. 

For instance:

If you take 50mcg of SR T3, your body may only absorb some fraction of the total (such as 25mcg or 30mcg of the original 50mcg). 

This typically doesn’t happen with the IR T3s. 


T3 is also found in combination with T4 in medications such as Natural Desiccated Thyroid. 

Natural Desiccated Thyroid (or NDT for short) is dosed differently than other thyroid medications and is referred to as “grains”. 

1 grain of NDT contains around 38mcg of T4 and about 9mcg of T3. 

It’s better to use grains as a unit of measuring the potency of NDT because each formulation has a different set of milligrams which equals 1 grain. 

For instance:

65mg of Nature-Throid = 1 grain while 60mg of Armour Thyroid = 1 grain. 

Don’t let this confuse you though, just realize that NDT contains both T4 and T3. 

Because your thyroid gland (when it is healthy) produces around 80% T4 and around 20% T3 it makes sense to supplement your body with similar ratios. 

This may be why patients who start taking T3 medication often feel much better compared to when they were on T4 medications by themselves. 


T3 fits into the categories of tests, medication, and hormones all in one. 

Understanding what T3 does and how it works is critical to understanding thyroid function in the body because it is considered to do all of the “heavy lifting”. 

Getting your physician to test for T3 and to prescribe T3 medication can be difficult, but certainly not impossible

If you are struggling to get help you can use this as a resource to help you find a knowledgeable physician

But now I want to hear from you:

Have you had your T3 tested? Were your levels optimal?

Are you currently taking T3 medication? How is it working for you?

Are you struggling to find a doctor willing to work with you?

Leave your comments below! 

#1. https://www.ncbi.nlm.nih.gov/pubmed/12915350

#2. ncbi.nlm.nih.gov/pubmed/6479377

#3. ncbi.nlm.nih.gov/pmc/articles/PMC329808/

#4. ncbi.nlm.nih.gov/pmc/articles/PMC3673746/

#5. ncbi.nlm.nih.gov/pmc/articles/PMC4699302/

#6. ncbi.nlm.nih.gov/pubmed/27700539

#7. ncbi.nlm.nih.gov/pubmed/27440910

#8. ncbi.nlm.nih.gov/pmc/articles/PMC3205882/

#9. ncbi.nlm.nih.gov/pmc/articles/PMC5167556/

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