Why is Free T3 test so important?

[North48]

Why is the Free t3 test so important? When I asked my dr's why they don't check my free t3 one dr said that if there is enough free t4 there won't be a problem (that was the drift I got of a very confusing dr's theory) and the other dr told me that if I had a conversion problem it would have shown up as a child a long time ago.  So why have 2 dr's told me it wasn't necessary?  I have a micro pituitary tumor 3x4 and my last tsh was 3.1 range .3-5.0, the Free t4 was 1.2 range .8-1.8 and the TPO was .5 range <9.0.  So why haven't I been able to get the right tests or have I gotten them?

They have told me I'm fine must be something else wrong but I have a lot of the symptoms of hypothyroidism. I have huge family history of thyroid problems,type 1 diabetes, RA,vitamin B12 anemia, and so on.

Thanks for any feed back I truely appreciate your time.

[gimel]

I may be off base, but I think that a lot of the approach to thyroid testing that we see today had its beginnings back when testing was not nearly as accurate.  Even though free T3 is the most active thyroid hormone, that largely regulates metabolism and many other body functions, correlates best with hypo symptoms, and is four times as potent as T4, it still is not a regular part of thyroid testing.   This continues even though the test for free T3 is now considered as reliable as other tests.  
Many doctors continue to use only TSH to determine thyroid status and medication amount.  The thinking is that TSH correlates with the level of T4 and T3 in the blood, so it is a good overall diagnostic for thyroid.  This has been shown to be inaccurate, many times over.  It is no better than an indicator, because TSH is a pituitary hormone that is affected by many variables.  Symptoms are not affected by TSH, they are affected predominantly by free T3.  Why not measure the hormone that correlates best to symptoms?
Many labs and doctors still use the old reference range for TSH, which was .5-5.0.  About 6 years ago the AACE recommended the range be reduced to .3-3.0. The new range is still not widely adopted.  Some areas of the Medical field seem to change very rapidly, while others don't seem to want to change at all.
Instead of treating patients' symptoms, many doctors using TSH as their predominant diagnostic, will only medicate patients to get them into the reference range.  Frequently this leaves patients still suffering from hypothyroidism.    
Sometimes doctors will also test for total T4 or free T4, assuming that if the level of T4 is adequate, the body will always convert to T3 adequately.  This is not always the case either,  and sometimes patients end up with a high level of T4 and inadequate levels of T3.  I was one of those for years until I learned about this problem and got my meds changed.

Many times I think it is a money issue.  Some insurance still will not cover a free T3 test, so the patient has to pay out of pocket.

Sometimes I get pessimistic about this whole problem area ever changing as needed, so that patients are treated based on their symptoms, tested for free T3 and free T4, and  medicated as required to achieve the Euthyroid state, which means neither hyper nor hypo thyroid symptoms.  

Sorry, I didn't mean to be so lengthy.  Hope this helps clear up some of your questions.

[North48]

Thank you so much, it does help me understand why.  I think I just need to keep looking for the right dr but it's really hard to find them.  This is so complicated !!!!

Thanks Again

[gimel]

You are very welcome.  Although posting a referral to a good thyroid doctor on this forum is a potential problem, you might have some success if you post a new message and ask for a PM (private message) for a good thyroid doctor in your area.  

[North48]

Sorry but I'm really new to this site and any other site. Can I post a PM here or do I have to go to post a question?