Had a chat with somebody who knows about thyroid and asked what he thought about reverse T3 tests. The answer he gave me is that there is an "active T3" test, and the T3 is in a form that will enter the cells (it is believed I may have receptor blockage) and that is what some thyroid specialists use. He could not remember the company doing it. Does anyone know of an active T3 test. I can't find anything. I am assuming he does not mean free T3.
Also many years ago I did the 24 hour urine test and got one of the lowest results my doc at the time had seen. Do many practitioners use that test these days.
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Free T3 is the free T3 that is available to be used by the cells, as opposed to Total T3 which measures the total of both bound and unbound/free T3. I wonder if that is what your friend means?
Only unbound “free” thyroid hormones are active and have an effect, though. So only the free thyroid hormones are measured (FT3 and FT4 – where “F” stands for “free”).
Did a GP or endo interpret the results? I've always thought it would be nice to know how to interpret urine test results for thyroid, but they rarely get a mention.
I just googled "how to interpret urine tests for thyroid hormones" and got quite a few results, but I haven't actually read any of them (yet).
It’s a bit like a saliva cortisol test that measures average output over 24 hours and supposedly better at assessing T3 levels as measures a total of separate 'frees' & 'bound', as opposed to measuring the peaks or troughs of 'free' and in the middle if you are lucky.
I read you can’t compare urine with blood because urine generally measures higher (I don’t know why). My endo asked that I did several 24hour thyroid hormone urine tests because my adrenals were so bad when I started medicating T3. I was his case study.
I also did several other 24 hour urines assessing kidney function, etc. My GP’s surgery always looked so surprised when I turned up with all this pee. Everyone else discreetly passed their tiny sample bottles over the counter and my 5 litre containers were so heavy, with adrenal issues I could hardly lift them! 🤣
I thought that standard practice with any kind of urine testing was to
a) Save all of it over 24 hours, and make sure it is well mixed up.
b) Measure the total volume. For example, say it was 2 litres/2000 ml. (Does that sound reasonable? I wouldn't have a clue!)
c) Take out 20 ml of it, measure whatever you want to measure in that 20ml then multiply the result by 100 to cater for the total 2 litres over 24 hours.
I really haven't a clue 🤷♀️ and was too ill at the time to be inquisitive. I guess it's much like serum bloods in that you have to look at the whole picture.
I was told at the time that the 24 hour urine test represented how much thyroid hormone actually makes it into the cells. My T3 and T4 were very very low. I have chronic lyme/CFS etc and have been told it is probably blocking receptors stopping T3 and T4 entering the cells.
The answer he gave me is that there is an "active T3" test,
This person you were speaking to has some peculiar terminology.
There is such a thing as a Reverse T3 test, but the test itself is expensive and pointless. There are many reasons for high Reverse T3 but most of those reasons are nothing to do with thyroid disease. greygoose and SeasideSusie know more about Reverse T3 than I do.
There is such a thing as a Total T3 test, but this measures mostly the inactive form of T3 which is attached to transport proteins that carry it around the body. The test is not terribly useful.
The test you need is called the Free T3 test, which is T3 stripped of its transport proteins which can enter T3 receptors anywhere in the body - every cell in the body has T3 receptors.
But can cell receptors still be blocked for T3? I always thought so. I think that is what I was told years ago when I got the 24 hr urine thyroid test done.
People used to say that Reverse T3 blocked T3 receptors. But it turns out that Reverse T3 and Free T3 have their own receptors and don't conflict in the way it used to be thought.
It depends on your definition of 'blocked'. Some call 'desensitised' blocked, as in T3 is unable to enter the cell. Receptors can become desensitised by too much FT3 or years of underuse for example.
Oh poor you. Yes, Lymne causes terrible inflammation which can mess with the enzymes that dictate how our thyroid hormones work. Also makes you vulnerable to so much more, ie gut issues, mould, other chronic infections, etc.
The standard urine test only measures total but there are others more comprehensive that measure the metabolites of T3 & T4 that gives more idea on their behaviours & how they are working.
About 70% of T3 & T4 are excreted as ‘frees’ in urine. The frees are the unbound so available for use and it is this activeT3 form that can enter the nucleus where it binds to a receptor and works its magic. However, even this test can't tell you for definite what amount or to what degree T3 has been uptaken and utilised.
Thanks. Yes I do have multiple infections. I also used to have high lindane (can also mess up thyroid tests) and nickel and other heavy metal problems which can mess up results too. Please can you tell me who does the more comprehensive tests for metabolites.
Don’t let their overseas address put you off. I think they also work through Regenerus or one of the other big ones. You would need a practitioner to organise and interpret the results. I haven’t had this exact test, only the DUTCH.
Thanks. That is useful. I have not been keeping up to date with thyroid stuff. I think it was the Dutch one that I did many years ago - think I did it through thyroid UK. At the moment I have no thyroid practitioner that could authorise the test. Have had to find a new thyroid practitioner recently as my CFS doc can't prescribe any more and the new practitioner does not do urine test - wasn't into my 0 TSH either and wants me to reduce the dose but that is another story. Was thinking a urine test could back me up. I don't think many practitioners use the urine testing now.
Hi, if on a high dose of t3 wasn’t really making you well would the total t3 test not show the inactive t3 as opposed to the active so that the high dose of t3 is needed although the blood test is over the top of the range? Just curious 😊 x
Along with humanbean I simply do not understand the meaning of "active" versus "inactive" T3 except as in bound versus free (unbound). It appears to be a concept unique to this thread!
Are you suggesting that Total T3 would rise while Free T3 doesn't, or at least, not proportionally, for some reason?
Yes, you didn't tell us what he did think about rT3 testing.
The only time high rT3 has anything to do with thyroid is when the FT4 is too high. So, what do you do? You reduce the levo. This might mean that you need to add in T3 - a whole nother discussion in itself - but if your FT4 reaches a certain level, you are going to have high rT3.
Other causes of high rT3 include:
* Chronic fatigue
* Acute illness and injury
* Chronic disease
* Increased cortisol (stress)
* Low cortisol (adrenal fatigue)
* Low iron
* Lyme disease
* Chronic inflammation
* Selenium deficiency
* Excess physical, mental and environmental stresses
* Beta-blocker long-term use such as propranolol, metoprolol, etc.
* Physical injury is a common cause of increased RT3
* Viruses, such as flu
* Starvation/severe calorie restriction
* Mistreated diabetes
* Cirrhosis of the liver
* Fatty liver disease
* Renal Failure.
* Fever of unknown cause
* Detoxing high heavy metals levels
* Etc. etc. etc.
I'm pretty sure he does mean Free T3, I can't see what else it could be. And, I'm not sure your friend knows as much about thyroid as you think he does. Sorry.
Thanks, from your reply I can only assume he must mean free T3 if there is no test for active T3.. He didn't think much of reverse T3 or urine test. He wasn't a friend.
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