Problem converting T3 and weight gain? - Thyroid UK

Thyroid UK

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Problem converting T3 and weight gain?



I've posted twice before which gives some more info about my current condition. I have a hospital checkup on Tuesday and am going to try and request some additional testing. My private Blue Horizon test 11 showed I have a Vit D and B12 deficiency (even though I've been supplementing heavily for about 5 months). It suggested i may have issues with absorbing vitamins.

My question here is about T3 and RT3. Would it be possible for my thyroid to be overactive, producing too much t4 but not properly converting to t3? Weight gain was an issue before diagnosis and i have gained 10kgs in the last year with treatment. Could the issue of weight lie in a lack of t3, slowing my metabolism?

Doctors don't believe my weight to be relevant and Im tired of not being taken seriously. I'm 21 and have gained 16kgs in 2-3 years due to this. I work out regularly and have recently gone gluten free but so far nothing has helped weight loss

This is the article that brought my attention to T3/RT3 and weight issues

4 Replies

g0courtney. If you can copy/paste some of your history into your Profile it gives members an idea of your condititon/treatment without reading past posts. :)

I am hypothyroid I cannot answer your question about weight gain caused through Graves. Members who have Graves will respond.

As you are concerned about RT3 - this is an explanation by a Scientist and Adviser to of how it arises which might be helpful:-

""Dr. Lowe: Some readers will not be familiar with reverse-T3, and I know from experience that many others harbor misconceptions about the molecule. Because of this, I have summarized in the box below what we know about reverse-T3. I've answered your question below the summary.

Conversion of T4 to T3 and Reverse-T3: A Summary

The thyroid gland secretes mostly T4 and very little T3. Most of the T3 that drives cell metabolism is produced by action of the enzyme named 5'-deiodinase, which converts T4 to T3. (We pronounce the "5'-" as "five-prime.")

Without this conversion of T4 to T3, cells have too little T3 to maintain normal metabolism; metabolism then slows down. T3, therefore, is the metabolically active thyroid hormone. For the most part, T4 is metabolically inactive. T4 "drives" metabolism only after the deiodinase enzyme converts it to T3.

Another enzyme called 5-deiodinase continually converts some T4 to reverse-T3. Reverse-T3 does not stimulate metabolism. It is produced as a way to help clear some T4 from the body.

Under normal conditions, cells continually convert about 40% of T4 to T3. They convert about 60% of T4 to reverse-T3. Hour-by-hour, conversion of T4 continues with slight shifts in the percentage of T4 converted to T3 and reverse-T3. Under normal conditions, the body eliminates reverse-T3 rapidly. Other enzymes quickly convert reverse-T3 to T2 and T2 to T1, and the body eliminates these molecules within roughly 24-hours. (The process of deiodination in the body is a bit more complicated than I can explain in this short summary.) The point is that the process of deiodination is dynamic and constantly changing, depending on the body's needs."


Your recent test suggests you are now hypothyroid. Did you get carbimazole reduced

That is a rather old article, and not a very good one. He gets all sorts of things wrong. He says, for example, that rT3 is a mirror image of T3. But, it's not. A different atom of iodine is removed than for making T3, but it's not a mirror image. I wouldn't take too much notice of that article, if I were you.

If your T3 is under range then yes weight will be an issue as T3 governs metabolism

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