I've never personally tested my RT3, and I heard mixed opinions about it. Some swear by it, others don't use it and think that a full thyroid panel with all the Ts, TSH and anti-bodies is sufficient.
I came across this as well:
When rT3 Measurements Are Not Accurate
rT3 is often analyzed by a process called immunoassay. This is known to show falsely elevated levels in people who are on thyroid medication and in people with autoimmune thyroid antibodies. Another analytic method called liquid chromatography-tandem mass spectrometry (LC-MS/MS) does reduce these errors but does not eliminate them.
What are your thoughts on RT3? Is it necessary to measure it and rely on it?
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Juliet_22
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It certainly used to be thought important but there are so many causes of high RT3 that even if it were to be found to be high then the cause would still be uncertain. It's also a very expensive test.
Just reading that article. Wow. Especially on cases who tried T3 only and generally how T3 has not worked for everyone. Thank you so much for sharing it!
rT3 can be high for a multitude of reasons ..only one of which is directly related to thyroid hormone levels/ dose.
a high result cannot tell you why it is high .
The 'thyroid' reason for high rT3 is 'too high' fT4 levels .. how high i too high ?.. its a relative not an absolute number .
But if rT3 is high because of 'too much' T4 ,then that can already be deduced from looking at fT4 in comparison to fT3 and TSH to seeing how good the conversion from T4 to T3 is.. and observe how conversion changes with different levels of T4..
So whilst it might be interesting additional information to know what rT3 is and track it ... it's expensive ,and basically not really needed, because it's much cheaper and easier to use information on dose / fT4 /fT3 / TSH.
There are some excellent replies (somewhere) on the forum previously written by greygoose and SeasideSusie which explain this much better than i have . Try the "Search HealthUnlocked" box for Reverse T3 .. set search to posts from ThyroidUK forum ...the search function is a bit rubbish but you'll probably find them anyway ,as the same replies have have been posted frequently over recent years.
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