Thyroid UK
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Significance of RT3 - please repost responses?

Two days ago, there was an excellent discussion/explanation of RT3 (and also, FT3), their roles, and what to look for when deciphering thyroid blood results. For the first time I felt like it had been explained in such a manner that my brain understood. I kept the discussion open so that I could apply it to my own tests when, alas, the discussion has poof! vanished. (The original poster appears to have "left the building" and took all their posts with them..sigh).

Can whomever who provided that excellent concise explanation please do so again?

Much appreciated!

2 Replies


It's annoying when informative posts are lost when a member deletes their HU account.  I think you'll have to repost the question "What is the significance of rT3?" and see whether the members who previously responded will reply again.

My understanding of rT3 is limited.  T4 converts in large proportion to T3 and smaller proportion to rT3.  rT3 is the body's brake on over converting T3 and becoming hyperthyroid.  During serious illness rT3 rises in order to lower FT3 to slow down metabolism to aid recovery.  There is a school of thought that high levels of unconverted T4 cause high rT3 to block T3 receptors.  Others vehemently disagree.


Thanks clutter. I will post again. The explanation in that thread was so good! Clear, concise and easily understood by "foggy brain". Sad to see it's gone. 


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