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Do You Have Thyroid Hormone Conversion Syndrome?

by | Oct 28, 2018 | Thyroid Disease


Normal Thyroid Labs, But Still Tired? You May Have Thyroid Hormone Conversion Syndrome

Dr. Shawn Soszka, Naturopathic Physician
When people think of thyroid problems, they naturally assume the thyroid gland is unable to make enough hormone for the body to function normally. Certainly, this scenario called hypothyroidism is a common condition affecting more than 20 million Americans.

Thyroid Symptoms

Symptoms include fatigue, poor memory, hair loss, feeling cold, weight gain, constipation, and dry skin. In most cases, the basic thyroid lab tests such as TSH and Free T4 will correctly identify this disorder.

But what if you have all the symptoms of hypothyroidism but have normal thyroid labs? Most doctors at this point stop looking at thyroid function. Many will assume depression is the cause and write a prescription for an SSRI or other mood regulating medication. There’s a really good chance that your doctor missed the real cause - thyroid hormone conversion syndrome.

Normal Thyroid Physiology

In a healthy thyroid, two thyroid hormones thyroxine (T4) and triiodothyronine (T3) are created and released to set the speed of cellular activity in the body. T4 makes up about 97% of thyroid hormone released from the thyroid. However, T4 doesn’t have a strong influence on metabolism or energy production. T4 must first be converted to T3 to have any significant effect on the body.

When this conversion process is slowed or limited in your body, you will experience the exact same symptoms as hypothyroidism. In most of these cases, the basic lab tests used to detect hypothyroidism show “normal” results.

Thyroid Hormone Conversion Syndrome Doesn‘t Involve the Thyroid Gland!

As I mention above, Thyroid Hormone Conversion Syndrome (also called Low T3 Syndrome) is not a problem with thyroid production, as T4 is produced in abundance. The problem is in the conversion process. However, most healthcare practitioners give no further thought to the thyroid hormone process beyond T4 production. As a result, they commonly overlook this condition.

This disorder is defined as a failure of T4 to adequately convert to the biologically active thyroid hormone, T3 that the body needs to function correctly. This T4 to T3 conversion takes places several tissues throughout the body, but mostly in the liver, kidneys, and intestines. We will look at the different causes of this low conversion activity and the lab tests that needed to correctly identify thyroid hormone conversion problems. Furthermore, I should mention that I discuss this topic in depth in chapters 3, 5 and 10 of my book, The Thyroid Fix. If you haven’t read it, I recommend checking it out on Amazon.com.

Proper thyroid testing helps you find and fix your fatigue!
Photograph by Gregory Pappas via Unsplash

The Symptoms Are The Same For a Reason

Even though the thyroid gland may be functioning normally in this situation, the symptoms of this T3 under conversion are the same hypothyroidism. The typical symptoms of fatigue, poor memory, hair loss, weight gain, and so on are all present.

This shouldn’t be a surprise because the end result is the same in both hypothyroidism and thyroid hormone conversion syndrome.  Not enough T3 is getting to the cells and as a result, all of the cells of the body operate at a reduced rate because T3 sets the rate of metabolism and energy production in the cells.

The difference between these two conditions is where the problem exists within the process of the thyroid system. Hypothyroid occurs within the thyroid and the conversion syndrome occurs in the tissue sites where T4 to T3 conversion takes place.

Why Typical Thyroid Labs Misses Thyroid Conversion Problems

In testing for thyroid conditions, conventional medicine only checks a single lab marker called thyroid-stimulating hormone (TSH). While TSH is helpful for uncovering the more significant thyroid diseases such as moderate to severe hypothyroidism, it has several limitations in providing a complete picture of thyroid function.

First, the accepted normal range for TSH can’t be agreed upon. Several endocrinology societies advocate a lower range than the labs use in their reports. If your doctor isn‘t aware of the new recommended range and looks at the so-called normal range the lab lists, he or she may miss your thyroid problem.

Second, TSH has limited value because it measures the demand for thyroid hormone and is not a measurement of the actual production or conversion of the two thyroid hormones, T4 and T3. I recommend ordering a comprehensive thyroid hormone panel when being testing.

“Most doctors miss thyroid hormone conversion syndrome because they don’t order the right blood tests.”

The Correct Way To Test Thyroid Function

Comprehensive testing includes measuring circulating T4 and T3 thyroid hormone levels. This profile should include TSH, Total T4, Free T4, Total T3, and Free T3. Measuring Reverse T3 is vital for identifying thyroid hormone conversion problems.

When we’re looking for evidence of thyroid hormone conversion syndrome, we need to see how much T4 is present and compare this to T3. Commonly, T4 levels are normal or even a bit high. While T3 levels are low. This lab pattern is a strong indication of poor conversion. TSH is often in the high normal range - but remember most labs use outdated ranges - so you really need to look at TSH above 3 as your body’s cry for help.

Comprehensive labs tell the whole story about your thyroid health.
Photograph by Hush Naidoo on Unsplash

Reverse T3 - The Key to Uncovering Thyroid Hormone Conversion Syndrome

What is reverse T3? In essence, its an unusable form of T3 that attaches to thyroid receptors on cells but has no effect on metabolism. Not only that, it actually shuts down the receptor, essentially putting the body into a mini-hibernation.

How is Reverse T3 (rT3) made? As mentioned earlier T4 convert to T3 for normal body function. But what exactly happens during this process? T4 carries four iodine atoms (thus the name “T4”). To become active thyroid hormone (3), one of these iodines needs to be removed. If it’s removed from the outer ring in becomes T3 - metabolically active and ready to go. However, if the iodine is removed from the inner ring, reverse T3 is created.   

The Free T3 to Reverse T3 Ratio

We’ll discuss what triggers the creation of rT3 in a moment. First, I want to review how we look at T3 vs rT3 when reviewing lab results. The normal range of reverse T3 is typically 9 - 25. Levels above the upper range indicate that there are problems with T4 conversion. But the key to all of this is to check the ratio of Free T3 to rT3. If the result is below 20, that confirms a conversion problem exists. I recommend using the ratio calculator at the “Stop The Thyroid Madness” website. I use this calculator daily in my clinical practice.

Reverse T3 can be in the normal range, but if free T3 or Total T3 are low you’ll still have a conversion issue. This becomes immediately evident when you use the calculator.


In Part 2

I hope you enjoyed this article and found it useful. There so much more to share you will you about the thyroid conversion process. In part 2 of this article, we’ll look at the common causes of poor thyroid conversions, effective therapies to improve conversion, and other important tests to monitor to track improvements. 

MEDICAL DISCLAIMER: The information on this website is not intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice. It is intended as a sharing of knowledge and information from the research and experience of Dr. Soszka, who encourages you to make your own health care decisions based upon your research and in partnership with a qualified healthcare professional.

Want to learn more? Buy The Thyroid Fix Today!


The Thyroid Fix BookMy new book, The Thyroid Fix, is an easy to follow guide on how to find and treat the underlying cause of your thyroid problems. I take a close look at how to find the original cause of your thyroid problem. Hint: it’s not usually in the thyroid itself! Additionally, I cut through all the confusion about the best thyroid diet. The answers to common questions ask including “Which lab tests provide the complete thyroid picture?” and  “Are there advanced tests that help find the cause of my condition?” are reviewed in detail. Most importantly, we’ll look at the most effective supplements, medications, and herbs to help you beat back fatigue, lose weight and get your life back.


Available on Amazon.com in Kindle and Paperback formats.

Dr. Shawn Soszka

Dr. Shawn Soszka

Naturopathic Physician, Licensed Acupuncturist

Dr. Soszka is a naturopathic physician, functional medicine practitioner, and licensed acupuncturist who has used a holistic approach to treat thyroid and digestive conditions effectively for over 20 years. He has helped thousands of patients restore their health and improve quality of life. Dr. Soszka's book, The Thyroid Fix is available on Amazon.com on Kindle and in paperback. He is currently accepting new patients at his clinic, NW Functional Thyroid Clinic, in southeast Portland, Oregon.