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T4 basics: the test, the medication, the hormone

T4 Thyroid Basics: The Test, The Medication, The Hormone

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Evidence-Based

This is video #3 in my thyroid beginner series and today it’s all about T4. 

T4 is essential in understanding your thyroid because it’s actually 3 different things in one. 

T4 is a prescription medication, a hormone that your body produces naturally, and a test that you can order. 

Learn the differences, what they mean and how they can help you manage your thyroid: 

What is T4?

T4 is the most abundant thyroid hormone that your body produces naturally (assuming it’s working properly). 

It’s also known as Thyroxine which is the “official” or scientific name. 

If you hear someone refer to thyroxine just realize that they are referring to T4 and vice versa. 

So what’s the big deal with T4?

T4 is important in understanding your thyroid because it’s involved in the thyroid feedback system. 

T4 thyroid hormone molecular structure

T4 is produced by the thyroid gland after the gland is stimulated by TSH from the pituitary

T4 then circulates through the body where it is converted (on demand) by your cells into the active T3 thyroid hormone. 

If you have low circulating T4 then you will have low circulating T3 and this will cause the symptoms of hypothyroidism!

Let’s dive into the various definitions of T4 and how understanding what they mean can help you as a patient…

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T4 the Hormone

As I mentioned previously, T4 is the most abundant thyroid hormone in your body. 

Your thyroid produces two major thyroid hormones: T4 and T3

About 80% of the thyroid hormone that your thyroid produces is T4 or Thyroxine. (1)

This leaves around 20% left as T3 (the primary active thyroid hormone). (2)

But why does your body produces so much T4 relative to T3?

The reason is most likely related to the control of the thyroid system. 

For instance:

T4, by itself, is not an active thyroid hormone. (3)

It must be activated, by enzymes, into the active T3 thyroid hormone. (4)

So your thyroid spits out some amount of constant T3 (directly from the thyroid gland) and then converts the rest of T3 that it needs from the abundance of T4 in the bloodstream. 

This way it can control how much thyroid hormone your cells need based on the demands that YOU put on your body. 

I think it’s most helpful to consider the analogy of a dam. 

In this analogy the dam is thyroid conversion (T4 to T3 conversion), T4 is the water behind the dam, and T3 is the water that is allowed through the dam

By setting up this system your body can titrate and carefully control thyroid function. 

And this makes sense, considering how important your thyroid is to your entire body! 

T4 the Test

But what about T4 as a test?

It should come as no surprise that we can test the amount of T4 that your body produces naturally (or the amount that you take by medication) through the blood. 

Doctors can do this by ordering what is known as a “free T4” test. 

High free T4 and low TSH in hashimoto's

This test is incredibly important in understanding how your thyroid is functioning because it is THE primary hormone that your gland produces. 

In many cases, I believe that the T4 (and T3) hold more value than the TSH when evaluating thyroid function. 

You can read more about how and why TSH can fall short as a predictor of thyroid function in thyroid beginner series #2 here

But what does T4 tell you when you measure it?

Several very important things:

#1. It gives you an idea as to how your thyroid gland is functioning. 

Your thyroid gland is stimulated by the pro-hormone TSH. 

This hormone tells your thyroid gland to produce both T4 and T3. 

If you test for T4 and find that it is low then it can tell you how responsive your thyroid gland is to TSH. 

The normal hypothyroid lab pattern is usually a high TSH accompanied by a low free T4

And this makes sense if you think about it:

If your thyroid can’t produce T4 then it responds by increasing the amount of TSH to try and overstimulate the gland to produce more hormone. 

But if your thyroid can’t produce thyroid hormone because it is damaged then the TSH will remain raised and your T4 will remain low. 

This is the “standard” pattern that most patients who have hypothyroidism or Hashimoto’s present with. 

#2. It gives you an idea as to how well your body is converting T4 into T3. 

We’ve already discussed how important T3 is for thyroid function in your body. 

And testing for Free T4 can help you identify issues with this conversion process. 

How does it help?

You can test both Free T4 and Free T3 and look at the ratio between the two of these hormones. 

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Your T4 should be in a “healthy” range (usually the top 50% of the reference range) and your T3 should be in about the same range. 

If you have issues with T4 to T3 conversion you may see your T4 increase while your T3 decrease. 

In cases where your body isn’t able to produce thyroid hormone, you may see both the T4 and the T3 low. 

But both situations may be a clue that your body isn’t converting as well as it should. 

#3. It gives you an idea if you are absorbing or utilizing thyroid medication that you are taking by mouth. 

T4 can, and should, be tested when you are taking thyroid medication by mouth. 

It goes without saying, but in order for your body to actually “use” thyroid hormone that you take by mouth, it must be absorbed by your body. 

There are several factors, including the time of day that you take thyroid medication, (5) that can impact the rate at which you absorb thyroid medication. 

You can easily determine if you are absorbing thyroid medication by checking Free T4 before you start medication and 8 weeks afterward. 

You should see your Free T4 increase as you take thyroid medication and you should see your TSH drop. 

If these things don’t happen then you may need to consider that you are not adequately absorbing your medication. 

Other factors such as supplements, calcium, (6) and food intake can all impact how well you absorb thyroid medication (and this is why it’s generally recommended that you take thyroid hormone on an empty stomach). 

You can learn other tips and tricks to help maximize thyroid hormone absorption here

T4 the Medication

T4 is also the most commonly used thyroid medication. 

Prescription thyroid medications, especially those used by conventional doctors, contain T4 thyroid hormone. 

Medications that fit into this list include Synthroid, levothyroxine, Tirosint, and Levoxyl. 

These medications contain ONLY T4 or Thyroxine and should be compared to other medications which contain either combinations of T4 and T3 or just T3 alone. 

T4 has become the most commonly used thyroid medication over the last 30 years or so (7) because it is felt to be the most “consistent” thyroid medication and because it has the longest half-life (which means it stays in your bloodstream the longest). 

But it should always be remembered that your body naturally produces both T4 and T3 and that replacing only T4 may be part of the reason that so many patients remain symptomatic despite taking thyroid medication. 

Doctors only use T4 because they assume that your body will have no issue in converting T4 into T3. 

But this logic doesn’t take into account that each person converts T4 into T3 at a different rate and that we aren’t all equal in that regard. 

The problem with T4-only medications is that newer studies have shown that many people who use T4 have a lower than normal T3 (8) (the active thyroid hormone) even though they have a normal TSH. 

This approach to thyroid hormone replacement may be part of the reason that so many patients remain symptomatic despite having a “normal TSH”. 

It should also be noted that you can safely use T3/T4 thyroid medications without negative side effects provided they are used appropriately. 

Conclusion

That concludes our discussion on T4 basics!

Just remember that while T4 is an important thyroid hormone for your body, it is not as powerful as T3 thyroid hormone. 

But it still has value in terms of testing and using T4-only thyroid medication. 

Some people are able to use T4 thyroid medication and feel great while others may need some T3 to feel optimal. 

If you have thyroid problems make sure that you can differentiate between T4 the test, T4 the hormone, and T4 the medication

Now I want to hear from you:

Have you had your T4 tested? Was it low or normal?

Are you taking T4 medication? Is it working for you?

Why or why not?

Leave your comments below! 

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

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

#3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4699302/

#4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3673746/

#5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4650787/

#6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3092723/

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

#8. https://www.thieme-connect.de/DOI/DOI?10.1055/s-0043-125064

what you need to know about t4 thyroid hormone
Why is there so much controversy surrounding thyroid treatment

The Thyroid Controversy: Where Doctors Go Wrong

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Evidence-Based

This is lesson #2 in my thyroid beginner series which is primarily designed for those who are building a foundation of knowledge in thyroid dysfunction or for those who have recently been diagnosed. 

Today we will be discussing why there is so much controversy surrounding thyroid treatment and why it can be difficult to get your doctor “on board”. 

Watch the video above for more info or read the text below if you prefer as well!

Please leave your questions in the comment section below so I can go over them in the next video!

Thyroid Controversy: Integrative vs Conventional Treatment

Why are so many thyroid patients unhappy with their current treatment?

Is it possible that our current approach or understanding of thyroid management is flawed?

I think this answer can be addressed by simply looking at how we approach and manage thyroid dysfunction and comparing that to other ways that we look at hormone imbalance in the body. 

Patients often find themselves in an unfortunate situation:

They have been diagnosed with thyroid issues and are experiencing thyroid symptoms even though they are already taking thyroid medication

If you fall into this situation you might be asking yourself this question… 

How is it possible for me to feel so terrible when my Doctor keeps telling me that my thyroid is “normal”?

And this is the thyroid controversy in a nutshell and it comes down to how Doctors look at and manage the thyroid.  

This approach to thyroid management has left thyroid patients frustrated which leads them to seek help on the internet, on forums, and on Facebook groups. 

With this in mind let’s take a look at how conventional doctors approach thyroid management and compare that to integrative doctors. 

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Foods to Avoid if you Have Thyroid Problems:

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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!

DOWNLOAD NOW

How Conventional Doctors Look at Thyroid Treatment

The standard and conventional approach, the approach that is taught in medical schools and residencies, is actually quite simple. 

I’ll outline it to you below (this is the way that I was taught and the way that most doctors are taught): 

  • If thyroid disease is suspected then check for a lab known as the TSH (thyroid stimulating hormone). 
  • If the TSH is high (defined as outside of the lab reference range) then initiate treatment. 
  • Treatment should always be done with T4-only thyroid medications such as Levothyroxine, Synthroid, or Tirosint
  • Adjust medication until the TSH is somewhere around 1.0 to 2.0. 
  • Any other symptoms related to thyroid disease (such as fatigue, weight gain, depression, constipation, cold skin, etc.) must be related to some other cause if the TSH is normal
  • Make adjustments to thyroid medication based on the TSH which is tested every 2-3 months. 

The main problem with this approach is that it is too rigid to allow for variability among patients. 

For instance:

How is it possible that all thyroid patients can do well on one medication?

Even when treating diseases such as cholesterol and high blood pressure Doctors have several sets of medications (1) that they will use and play around with but when it comes to the thyroid they are set on using one medication. 

Is it possible that some patients differ in their ability to utilize thyroid medication?

Some patients may react to the fillers or dyes in certain medications or vary in their ability to absorb medication from gastrointestinal issues. 

Problems such as lactose intolerance, Celiac disease or SIBO (2) can all influence how the body absorbs these medications. 

Is it possible that genetics may play a role in which medication works best for each person?

Doctors have no problem ordering genetic tests which outline how you metabolize anti-depressants, but they fail to consider that individuals can vary in how they metabolize hormones in the body. 

It is well known that individual genetics impact the pharmacokinetics and pharmacodynamics of medications and hormones in the body (3)!

These are just some of the reasons that taking such a rigid approach doesn’t make sense from a logical standpoint, but there are other reasons as well. 

Does Focusing on the TSH Make Sense?

The reliance upon TSH as a sole marker for thyroid function may not make sense when you compare it to other pituitary hormones and how Doctors treat those issues. 

To understand this let’s briefly discuss what TSH is and how it works:

TSH is known as thyroid stimulating hormone and it is secreted by the pituitary gland in your brain. 

TSH acts directly on the thyroid gland to stimulate the release of thyroid hormone (4).

So the higher your TSH is the more “stimulation” your thyroid gland gets and the more hormone your produce. 

But TSH isn’t the only hormone that is secreted by the pituitary gland which acts in a similar way. 

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Hormones such as LH, FSH, and ACTH all act to “stimulate” other organs to release their target hormones

But what’s interesting here is that whenever we look at other hormones, such as testosterone, we don’t care what the pituitary stimulating hormone level is, we care about the level of the hormone in the body (5)!

For instance:

If you feel that you have low testosterone in your body would it make sense for your Doctor to check your pituitary stimulating testosterone hormone or to directly check testosterone levels in the body?

Logically, it makes sense to check for the hormone. 

But that’s not what we do with the thyroid. 

Instead of looking at the hormone levels in your body, we check for the pituitary-stimulating hormone TSH. 

And instead of adjusting the dose based on how much hormone is in your blood, conventional doctors adjust it based on the TSH. 

But there’s a problem with that:

Studies have shown that patients who are treated with T4 thyroid medication to a “normal” TSH still have lower than normal free thyroid hormone levels which may account for the trouble that many patients experience. 

This can largely be solved with the use of both T4 and T3, but physicians still refuse to use these medications.

But back to the way that physicians normally dose and look at other hormones in the body for a minute. 

Consider these examples:

The TSH still has value and still should be checked in patients, but it may not be the single best marker to assess thyroid function in your body. 

How Integrative Doctors Look at Thyroid Treatment

So now that you understand how conventional Doctors (endocrinologists and primary care physicians) look at thyroid management we can compare that to how more integrative doctors evaluate patients with thyroid disease. 

And by integrative doctors, I am referring to doctors that may have extra training (outside of residency) in anti-aging medicine, integrative medicine or functional medicine. 

The problem with this type of training is that it is not “standardized” which means that not all “integrative doctors” look at each patient the same. 

Some doctors have used the term functional or integrative as a marketing tactic to simply get more patients even though they may not use a different approach from conventional physicians. 

But in an ideal world, your doctor should be evaluating you in the following way: 

  • Test for more than just the TSH – When evaluating your thyroid your free thyroid hormones (T3 and T4) give valuable insight as to how your body is absorbing and converting thyroid hormone. These free thyroid hormones (according to newer studies) track more closely with better outcomes when compared to other factors. 
  • Take into account individual genetics and preferences – Certain individuals are not able to convert or activate thyroid hormone at the same rate as others. SNPs in genes that control deiodinase enzymes can impact how you respond to T4-only thyroid medication (9). It is estimated that up to 15% of the population varies in their ability to convert T4 into the active T3 thyroid hormone. 
  • Take into account environmental factors such as stress, sleep, and diet – Lifestyle factors impact not only your thyroid but other hormones in your body as well! Your doctor should be treating you with more than just medications and supplements and should focus on the food that you put in your mouth and how you manage your stress. If they don’t address or ask about these questions then it may be time to seek a second opinion. 
  • Use more than just T4-only thyroid medications – In terms of thyroid medications, there is much more than just Synthroid and Levothyroxine. Other medications include NDT and T3/Cytomel/liothyronine. These thyroid hormones can be safe and incredibly effective if used appropriately. 

As a patient, which approach would you rather have?

The rigid approach of conventional medicine is algorithmic, and the more individualized/integrative approach which is fluid and dynamic. 

So What are you Supposed to Do? 

So what are you supposed to do if you feel terrible and your Doctor isn’t willing to work with you?

Learning and reading are steps in the right direction, but it’s not a substitute for a knowledgeable doctor who can guide you through the process. 

Your best bet is to seek out a physician who can help you and one who takes this more integrative approach. 

Unfortunately, these types of doctors can be very difficult to find and they often don’t take insurance. 

In order for these doctors to obtain this type of knowledge they usually have to do extra work and training after residency. 

This means that not all physicians are equal in their understanding of these concepts which means they can be difficult to find. 

I’ve put together a resource here that you can use to help find a knowledgeable physician in your area

Before you ask, I don’t know any or have personal recommendations to give you, or I would do so happily!

Because physicians have to learn this on their own we don’t have a secret group where we all talk or discuss patients. 

Conclusion

If you are struggling with your current thyroid management then it may be time to seek out a second opinion. 

Patients who have gone this route often report an increase in quality of life, an increase in energy, a reduction in weight, and many other benefits. 

Don’t waste the best years of your life with physicians who don’t take your complaints and symptoms seriously!

Life is too short and your health is too important. 

Now I want to hear from you:

Are you struggling with the current conventional approach?

Do you have questions about the integrative approach?

Which has worked for you? Which hasn’t?

Leave your comments below! 

#1. https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0072414/

#2. https://www.ncbi.nlm.nih.gov/pubmed/28153426

#3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5299682/

#4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3433956/

#5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4772354/

#6. https://www.ncbi.nlm.nih.gov/pubmed/393456

#7. https://www.ncbi.nlm.nih.gov/pubmed/3139571

#8. https://www.ncbi.nlm.nih.gov/pubmed/6323158

#9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1578599/

the thyroid controversy explained: where doctors go wrong
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