High Reverse T3 and What To Do About It

As a thyroid naturopath, reverse T3 is a topic I get asked about all the time. In fact, ‘what is reverse T3?’, ‘what causes high reverse T3?’ and ‘how do you lower reverse T3?’ are among my most frequently asked questions. This is because reverse T3 plays an integral role in thyroid health, yet sadly, much confusion and misunderstanding surrounds its existence and role in the human body. In this article today, I’m going to explore some of the causes of high reverse T3, and what you can do about it.

But first, a quick recap - what is reverse T3?

Reverse T3 is an inactive form of our thyroid hormones. The thyroid gland contains follicular cells which produce two main hormones: T4 and T3. T4 accounts for approximately 80% of the thyroid hormone produced by the thyroid gland, while T3 makes up the remaining 20%. Certain conditions (such as iodine deficiency) can alter this ratio, but an 80:20 split is considered typical of a well-functioning thyroid. Once they have been produced in the thyroid, T4 and T3 are released into circulation, so they can do work in the body. T3 is an active hormone, meaning it is ready to be used by your body’s cells immediately. T4 on the other hand, is considered a ‘prohormone’, as it needs to undergo an additional process called deiodination in order to be converted into its active form, T3. This is where the majority of T3 in the body comes from.

Deiodination is the process in which an iodide molecule is removed from the thyroid hormone via enzymatic activity. This process can either activate or inactivate the thyroid hormone, depending on which enzyme is involved:

• Deiodinase 1 (D1) can either activate or inactive thyroid hormone, converting it to either T3 or Reverse T3.

• Deiodinase 2 (D2) is the major activating enzyme, converting T4 into T3.

• Deiodinase 3 (D3) inactivates thyroid hormone by converting it into Reverse T3.

Together, the three deiodinase enzymes control how much active thyroid hormone is available in any given tissue at any one time. This is important because it means different tissues can have different levels of thyroid hormone, according to their needs - I’ve summarised these enzymes in further detail below.

*Note: There are two other mechanisms that are also thought to control thyroid hormone metabolism (conjugation in hepatic and renal tissue, as well as antioxidant enzyme systems), however I won’t go into these in this article.

Note: Reverse T3 is normal!

Although reverse T3 is inactive, it is still a normal product of thyroid hormone metabolism. It is therefore normal to have a certain amount of reverse T3 (in fact, production of reverse T3 is one of the ways in which the body protects itself against hyperthyroidism) - the problem occurs when we have too much reverse T3 relative to our active T3. Some have theorised that reverse T3 and active T3 compete for receptor sites at a cellular level, meaning an excessive amount of reverse T3 may limit the amount of active T3 that can act on the cell. If T3 cant bind and act on a cellular level, symptoms of hypothyroidism may result. I’ve included a diagram below to help illustrate this.

As you can see from the diagram above, when there is too much reverse T3 relative to active T3, a situation may occur in which there are less receptor sites available for T3 to bind to and act on the cell.

Certain factors can up-regulate or down-regulate the activity of our deiodinase enzymes, altering the amount of active or inactive thyroid hormone produced. When D2 is down-regulated and D3 is up-regulated, we produce less T3 and more reverse T3, resulting in this sort of ‘reverse T3 dominance’.

Factors or conditions that may be associated with increased reverse T3 (either as a cause or consequence) include:

• Selenium deficiency

• Zinc deficiency

• Iron deficiency

• Stress and its associated hormones (cortisol and adrenaline)

• Depression

• Certain medications (such as prednisone and other glucocorticoids, Amiodarone and certain beta-blockers)

• Starvation

• Crash dieting, prolonged fasting, very low carbohydrate diets and yo-yo dieting

• Excessive exercise

• Inflammation

• Chronic illnesses (including chronic fatigue syndrome and fibromyalgia)

• Hepatic or renal dysfunction

• Oxidative stress

• Euthyroid sick syndrome

• Metabolic disorders such as diabetes, leptin resistance and Metabolic Syndrome

• Hypoxia

• Advanced age

This is not a complete list - As I mentioned before, our understanding of reverse T3 is still in its infancy and there is much research to be done. What we do know is that reverse T3 is a normal part of thyroid hormone metabolism, but that abnormal elevations in reverse T3 production may reflect an issue in one of the areas listed above.

What can be done about it?

This is perhaps the most important topic when it comes to reverse T3 - what can be done about it? From a naturopathic perspective, the answer is to identify and treat the cause (‘tolle causam’ - one of the principle philosophies guiding my practice as a naturopath). Whether its a nutritional deficiency, stress or a history of long-term crash dieting, the only way to fix the issue is to address what’s causing it in the first place. This is the fantastic thing about the list above - MOST of the factors listed are variable factors, meaning we have the potential to do something about them. As you can see though, there are many potential causes (and often, more than one factor may be at play), so I encourage you to work with a suitably-qualified healthcare practitioner who can help you investigate, identify and address the cause. Instead of ‘shooting in the dark’, working with your healthcare practitioner will better enable you to identify what factors need to be addressed, saving you time, money and a lot of frustration! Lastly, please remember that correcting elevated reverse T3 can take time, but ultimately, if reverse T3 is an issue for you, addressing these factors will be worth it in the long run. As the saying goes, “a year from now, you’ll wish you started today”!

Niki x

ps, for more on the topic of reverse T3, click here (or here for more info about factors affecting thyroid hormone conversion!).

*Note: There are two other mechanisms that are also thought to control thyroid hormone metabolism (conjugation in hepatic and renal tissue, as well as antioxidant enzyme systems), however I won’t go into these in this article.

*Note: There are two other mechanisms that are also thought to control thyroid hormone metabolism (conjugation in hepatic and renal tissue, as well as antioxidant enzyme systems), however I won’t go into these in this article.

*Note: There are two other mechanisms that are also thought to control thyroid hormone metabolism (conjugation in hepatic and renal tissue, as well as antioxidant enzyme systems), however I won’t go into these in this article.

*Note: There are two other mechanisms that are also thought to control thyroid hormone metabolism (conjugation in hepatic and renal tissue, as well as antioxidant enzyme systems), however I won’t go into these in this article.

*Note: There are two other mechanisms that are also thought to control thyroid hormone metabolism (conjugation in hepatic and renal tissue, as well as antioxidant enzyme systems), however I won’t go into these in this article.