What does “Euthyroid” Mean? Definition, Symptoms & More
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What does “Euthyroid” Mean? Definition, Symptoms & More

If you have thyroid disease then understanding what euthyroid is incredibly important. 

If you aren't in a euthyroid state then you may suffer from the symptoms of hypothyroidism such as weight gain, fatigue, hair loss, dry skin and more. 

This article will teach you everything you need to know about this term including how to determine if you really have normal thyroid function, the symptoms associated with thyroid problems and how to test for thyroid issues...

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What Does Euthyroid Mean?

Euthyroid is a word you probably are not familiar with but it's an incredibly important term if you have any sort of thyroid disease. 

Euthyroid is the term given to describe a state of normal thyroid function in the body. 

Nothing more, nothing less. 

But why is it so important?

Because getting back to "normal" is the goal if you have any sort of thyroid disease! 

Let's use a simple case of Hashimoto's Thyroiditis as an example to illustrate this point. 

Let's say that you have recently been diagnosed with Hashimoto's thyroiditis and as part of this disease you are experiencing fatigue, weight gain, depression and menstrual problems. 

So you go to your Doctor to get treatment and to "fix" these problems. 

What you may not realize is that these symptoms are caused by a condition known as hypothyroidism which means you don't have enough thyroid hormone in your body

So what is the treatment?

The treatment is to take thyroid medication to bring your thyroid hormone levels back up to a normal level and to the point that these symptoms fade. 

In simple terms, you are going from a hypothyroid state to a euthyroid state with the help of medication (and probably some other therapies such as diet, supplements and so on). 

This may sound simple, but the problem comes when we try to define what "euthyroid" means based on lab tests. 

The standard approach is to identify a state of "euthyroidism" or "normal thyroid function" based on one simple lab test. 

Thyroid stimulating hormone or the TSH for short

It turns out that the TSH falls short as an accurate measurement of thyroid function but we'll talk more about that in a minute. 

Euthyroid Lab Levels (When do you Know your Thyroid is Normal?)

Typically, thyroid function is never really an issue or something that you give a second thought to unless you have a problem with it. 

But when you do have a thyroid issue it becomes a big problem. 

Because of this, defining what "normal" means is actually very important. 

The good news is that thyroid function can be easily assessed through certain lab tests

Tests such as Thyroid Stimulating Hormone (TSH) are often used by conventional doctors to determine thyroid function. 

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But is this the best way to measure thyroid status in the body?

Conventional Doctors will answer YES, but newer studies have shown that it may not be quite that simple

One of the main problems with TSH testing is that it ignores free thyroid hormones in your body. 

And this is important because free thyroid hormones do all of the heavy lifting when it comes to thyroid function.

And things get further complicated when you realize that your TSH can be normal when your free thyroid hormones are low

TSH also suffers as an indicator of thyroid function because it doesn't take into account the following: 

  • Peripheral thyroid conversion (is your body converting T4 into T3)
  • T3 status in the body (is T3 being utilized by your cells or is it competing with reverse T3 metabolites)
  • Sensitivity of the pituitary gland to thyroid hormone compared to other tissues

When you look at all of these factors closely it's easy to see why the TSH may not be the best test for every single person. 

Instead, when evaluating your thyroid, you'll want to look at more than just the TSH. 

I recommend assessing all of the following thyroid lab tests: 

  • Free T3 & Total T3 - Perhaps the most important measure of thyroid function that you can look at. T3 is the most active thyroid hormone in your body. 
  • Free T4 - T4 is less biologically active when compared to T3 but still functions as a reservoir for T4 to T3 conversion. 
  • Reverse T3 - Reverse T3 competes with T3 for cellular binding and high levels may blunt thyroid function. 
  • Thyroid antibodies - The presence of thyroid antibodies may indicate autoimmune disease or other issues and should be evaluated if thyroid disease is suspected. 

Euthyroid When using Thyroid Medication

Determining a state of euthyroidism becomes difficult when thyroid medication is used. 

Why?

Because the addition of thyroid medication influences standard thyroid measurements and not always in predictable ways. 

We know that if you take thyroid medication (such as Levothyroxine) this will alter the normal regulatory systems in your body. 

Your body will react by reducing your TSH (due to negative feedback loops) and also by increasing your serum free T4. 

Doctors have used this logic to guide their treatment of certain thyroid medications. 

They believe that if they provide your body with enough thyroid medication to sufficiently lower your TSH to a pre-defined "normal" range that you are now considered to be "euthyroid" or "normal". 

But is this a fair assumption?

Studies have shown that this approach probably isn't fair, at least not for many people. 

We know that if we give certain people thyroid medication, even enough to lower their TSH to the "normal" range that these people STILL have lower levels of free thyroid hormones in circulation when compared to healthy adults

We also know that many of these patients, despite having a "normal" TSH, still endorse symptoms such as fatigue, weight gain, depression and so on. 

So how can we honestly look at someone and tell them that they are "normal" when they have lower than normal free T3 and free T4 levels and the symptoms of hypothyroidism?

The answer is we probably need a better approach. 

A better approach takes into account more than just the TSH (thyroid stimulating hormone) as a measure of complete and normal thyroid function. 

You will most likely find that you feel much better when you look at a combination of factors designed to determine if you really are "euthyroid" such as:

  • Your free thyroid hormones (free T3 and free T4)
  • Your TSH (yes it's still important)
  • Your symptoms (how are you actually feeling?)

If you combine all of these factors together you are much more likely to have success when using thyroid medication. 

But do your best to look beyond the TSH as a measure of "euthyroidism" especially if you have a normal TSH but still remain symptomatic. 

Is Being Euthyroid Associated with Symptoms?

The answer to this is no, but it depends on how you define euthyroid. 

If you have normal thyroid function then you should NOT experience any symptoms relating to thyroid function (but that doesn't mean you can't have fatigue from some other cause). 

But if you define euthyroid as having a normal TSH, then it may still be possible for you to experience symptoms such as fatigue, depression, brain fog, etc.

How can this happen?

It's entirely possible that even though you have a normal TSH you may still suffer from other conditions such as low free T3 or low free T4. 

And because these thyroid hormones do all the work in your cells, it's possible to feel poorly with a normal TSH but lower than normal free thyroid hormones. 

The state of euthyroid is often confused with a condition known as euthyroid sick syndrome. 

You can differentiate these two terms by realizing that euthyroidism refers to a state of normal thyroid function while euthyroid sick syndrome is a disease state. 

Euthyroid Sick Syndrome vs Euthyroidism

Euthyroid sick syndrome is a condition which occurs in people who have an illness

When you have an illness your body reacts by slowing down thyroid function, blunting thyroid conversion and slowing down your metabolism. 

It does this probably as a protective mechanism to help your body fight off infection or to help heal. 

I always say, if you are seriously sick it's more important for your immune system to function than it is for you to grow your hair or nails. 

Doctors have noticed these changes and refer to them as "euthyroid sick syndrome" which is their way of saying that the thyroid looks abnormal but it's really not. 

The term "euthyroid sick syndrome" is probably a misnomer in the sense that it's NOT a normal thyroid condition and you can read more about that here. 

The bottom line?

When you are sick your thyroid will respond by making certain changes which can be picked up through routine thyroid blood tests. 

This doesn't necessarily mean you have a thyroid issue, but it's a good idea to retest your thyroid once you start feeling better. 

Can you be Euthyroid but Still have Hashimoto's Thyroiditis?

Hashimoto's thyroiditis is an autoimmune disease of the thyroid gland which results in the destruction of your thyroid slowly over a period of years. 

Chronic inflammation and damage to the thyroid gland usually result in the need for thyroid hormone medication. 

This damage often results in a hypothyroid state (meaning you will need to take thyroid medication to bring yourself back into the euthyroid state). 

One of the big problems with Hashimoto's thyroiditis has to do with when to start thyroid medication. 

It is well known, especially among Endocrinologists, that patients with Hashimoto's thyroiditis often experience the symptoms of hypothyroidism long before their labs actually show it

This results in a period of time where Doctors are reluctant to start thyroid medication even though it's obvious (based on symptoms) that you may need it. 

This confusion regarding when to start thyroid medication stems from the reliance upon TSH as the sole definition of euthyroidism in the body. 

In reality, if you check these patients with more than just the TSH you will often find that they have lower than normal circulating levels of T3 and T4 which would be an indication to initiate thyroid medication treatment. 

So can you be euthyroid and still have Hashimoto's?

The answer is yes, but again it depends on how you define the state of euthyroidism. 

If you have Hashimoto's and you are experiencing the symptoms of hypothyroidism then starting treatment may be a viable next step. 

Can you be Euthyroid but Still have a Goiter? 

Yes, but as always it depends. 

In general, a goiter just refers to an enlargement of your thyroid gland (this is the definition)

But what you need to realize is that you only have trouble with thyroid hormones if your thyroid disease causes a problem with your thyroid gland. 

Simple thyroid conditions such as a thyroid goiter, thyroid nodule and even thyroid cancer usually do NOT result in changes in thyroid hormone levels. 

What does this mean?

No change in thyroid hormone = no symptoms of hypothyroidism/hyperthyroidism = euthyroid state. 

But just because most people don't experience symptoms associated with these conditions doesn't mean that you can't. 

Some patients with thyroid goiter may experience the symptoms of thyroid disease. 

As always, the best way to measure thyroid function is to test your thyroid labs! 

Conclusion

Euthyroidism refers to a state of normal thyroid function in your body and it should be your goal to stay at this level. 

There seems to be a problem, especially among physicians, when we attempt to define what that actually means. 

Given our understanding of thyroid physiology, it's probably best to look at multiple factors including thyroid lab tests (more than just the TSH) and patient symptoms when determining if someone is truly euthyroid. 

It's also important to realize that even though you may have a thyroid issue (such as a thyroid nodule) doesn't mean that your issue is causing problems with thyroid hormone production

Only conditions which alter thyroid hormone production or conversion will result in hypothyroidism or hyperthyroidism. 

Now I want to hear from you:

Are you euthyroid?

Are you struggling with other thyroid diseases?

Do you have an abnormal TSH but still feel poorly?

Have your free thyroid hormones been assessed?

Leave your comments below! 

Westin Childs
 

Dr. Westin Childs is a Doctor of Osteopathic Medicine. He provides well-researched actionable information about hormone-related disorders and formulates supplements to treat these disorders. He is trained in Internal Medicine, Functional Medicine and Integrative Medicine. His focus is on managing thyroid disorders, weight loss resistance, and other sex hormone imbalances. You can read more about his own personal journey here.

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