Reverse T3 (rT3): Should it be measured in patients with hypothyroidism?

[Nelson Vergel]

There is a lot of controversy about whether reverse T3 (rT3) should be measured to assess hypothyroidism. The normal thyroid gland secretes T4 (an inactive precursor), T3 (the active hormone), and reverse T3, a biologically inactive form of T3 that may block T3 from binding to the thyroid hormone receptor. Most of the circulating T3 is derived from 5′-deiodination of circulating T4 in the peripheral tissues by type 1 deiodinase. Deiodination of T4 can occur at the outer ring (5′- deiodination), producing T3 (3,5,3′-triiodothyronine), or at the inner ring, producing reverse T3 (3,3,5′-triiodothyronine) by type 3 deiodinase. Type 2 deiodinase in the pituitary also converts T4 to T3 and is regulated differently from type 1 deiodinase.

Many years ago, endocrinologists realized that in severe illnesses, type 3 deiodinase increases and rT3 is often high and T3 is often low. Endocrinologists termed this “sick euthyroid syndrome” and noted that it was common in many types of chronic illnesses, especially in patients hospitalized in intensive care units. It was usually recommended that these patients not be treated with thyroid hormone and in most cases, the elevated rT3 resolved when the patients' health returned.

MORE HERE

 

[Mr. T]

I'm glad you posted this, Nelson. I've been reading TiredThyroid (thanks, Orrin) and this is one of the areas of thyroid debate.

The author has done a lot of research (she is a former data analyst and cites her sources) - here are some of her thoughts:

A reverse T3 ratio greater than 20 does not indicate good health any more than a normal TSH does

Reverse T3’s role in the body "Normal, healthy people produce reverse T3, it is not poison, and it is a normal pathway for the breakdown of T4. It is actually abnormal to have no reverse T3"

Reverse T3 and the “T3-only” protocol - "The reverse T3 ratio is a nonsensical number because the ratio can be low when Free T3 is high or Free T3 is low. A high FT3 and a low FT3 are different conditions and should not be treated the same way."

Reverse T3: Side Effects of T3-only (or why you need T4 too) - she addresses "clearing" rT3 and T3-only protocols

I'm hoping some of the thyroid gurus will chime in - thyroid is complex and confusing to me.

 

[OMI100]

I'm glad you posted this, Nelson. I've been reading TiredThyroid (thanks, Orrin) and this is one of the areas of thyroid debate.

The author has done a lot of research (she is a former data analyst and cites her sources) - here are some of her thoughts:

A reverse T3 ratio greater than 20 does not indicate good health any more than a normal TSH does

Reverse T3’s role in the body "Normal, healthy people produce reverse T3, it is not poison, and it is a normal pathway for the breakdown of T4. It is actually abnormal to have no reverse T3"

Reverse T3 and the “T3-only” protocol - "The reverse T3 ratio is a nonsensical number because the ratio can be low when Free T3 is high or Free T3 is low. A high FT3 and a low FT3 are different conditions and should not be treated the same way."

Reverse T3: Side Effects of T3-only (or why you need T4 too) - she addresses "clearing" rT3 and T3-only protocols

I'm hoping some of the thyroid gurus will chime in - thyroid is complex and confusing to me.

You beat me to the punch and did a much better job than I could have of referencing her discussion on his subject.
From my perspective she has one of, if not the best Thyroid site out there.
While NOT a DR she has spent a number of years doing deep research in the subject.
All her post/comments are backed up with research / studies from reputable sources.
Her book goes deeper into some of the areas that she covers on the web site.
Each chapter of the book will have multiple pages of footnoted references at the end.
The book could well be a Doctoral Thesis on the physiology of the thyroid....
She knows more about the thyroid than a large majority of the MDs out there.....
http://www.tiredthyroid.com/about-me
http://www.tiredthyroid.com/cv.html
http://www.tiredthyroid.com/doctors-review

 

[apsjiml]

There is a lot of controversy about whether reverse T3 (rT3) should be measured to assess hypothyroidism. The normal thyroid gland secretes T4 (an inactive precursor), T3 (the active hormone), and reverse T3, a biologically inactive form of T3 that may block T3 from binding to the thyroid hormone receptor. Most of the circulating T3 is derived from 5′-deiodination of circulating T4 in the peripheral tissues by type 1 deiodinase. Deiodination of T4 can occur at the outer ring (5′- deiodination), producing T3 (3,5,3′-triiodothyronine), or at the inner ring, producing reverse T3 (3,3,5′-triiodothyronine) by type 3 deiodinase. Type 2 deiodinase in the pituitary also converts T4 to T3 and is regulated differently from type 1 deiodinase.

Many years ago, endocrinologists realized that in severe illnesses, type 3 deiodinase increases and rT3 is often high and T3 is often low. Endocrinologists termed this “sick euthyroid syndrome” and noted that it was common in many types of chronic illnesses, especially in patients hospitalized in intensive care units. It was usually recommended that these patients not be treated with thyroid hormone and in most cases, the elevated rT3 resolved when the patients' health returned.
MORE HERE

A few things that I would like to point out when it comes to elevated rt3 low free t3. or lower free t3. #1 free t3 is the active form of thyroid and the interference it has on current essays unless it is lc-ms/ms is reverse t3. They look almost identical and just testing free t3 may not give an acurate readinf That is the big reason why a person should test free t3 amd reverse t3. Otherwise free t3 could look good but it could br falsely elevated because of rt3. #2 elevated reverse t3 and deiodinase ( thyroid conversion) issues have many causes including gene defects , low iron , low growth hormone , low testosterone , any inflammation issues - back pain to anything that involves inflammation. Actually above that anyone with pituitary dysfunction or Thyroid dysfunction such as hashimotos for that matter will lack deiodinase and will have a conversion issue. They have even discovered some people witb conditions like pulmonary fibrosis for example actually lack deiodinase within the lung tissue for example. So , to get a complete picture you really need a full thyroid panel with total and free t3. ( the reason for that is because some patients have elevated thyroid binding globulin or t3 anyobodies that may give false low total t3 but yet false high free t3 and you want to test reverse t3 , tsh free and total t4.