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  • Anonymous
      Post count: 93172

      Hi Ed

      Parts of your post sounds familiar! With ATDs my T4 has worked its way back to the low end of the normal range, but my TSH refuses to work its way up into the normal range. I haven’t had the T3 test. Maybe I should ask my dr. about that. It has me wondering also.


        Post count: 93172


        I think Glynis has posted quite a lot about the free T-3. If you sort
        through her past posts I think you will find her information very helpful.

        Best regards,

        Valerie L

          Post count: 93172

          Hi, Ed!

          If you’re referring to the “Your Thyroid, A Home Reference” (Wood,
          Cooper, Ridgway), the Free T3 test info is briefly discussed on pages
          8-9: “In order to estimate the amount of free active hormone, a blood
          test called the T3 resin uptake or Thyroid Hormone Binding Index (THBI)
          is used. These are inexpensive, indirect methods of estimating the
          proportions of active and inactive hormone. When more precise
          information is required, it is also possible to measure your blood
          level of free thyroid hormone, as well as the concentrations of the
          thyroid-binding proteins themselves. The most important of all these
          thyroid-function blood tests is the measurement of TSH.”

          Sorry that I can’t provide you with more info than that.
          Wishing you health and happiness, Debby

            Post count: 93172

            This site has explanations of all the tests and a lot of other information.

              Post count: 93172

              I am curious if anyone is familiar with this type of blood test. My
              Free T4 (FT4) and TSH have been consistently been low since stopping
              the ATD medications. At the time of diagnosis almost a year ago the
              Free T4 was high with the TSH level at undetectable; common levels for
              hyperthyroid, Graves Disease. The ATD dropped the Free T4 but the TSH
              never increase past the very low end of normal; currently standing at
              .51 with the Free T4 at .81. My doctor ordered a “Free T3” test, which I
              have not yet had done. I looked in the “Your Thyroid” book and it did
              not even mention this blood test. Trying to sort this out; you would
              believe the TSH would be cranked up more with such a low T4; but it
              isn’t. Perhaps this is why at times I feel hyper and hypo at the same
              time. Has anyone else had low T4 and high T3?


                Post count: 93172

                The T3 thyroid hormone is the one that activates cell metabolism — not the T4. One of my endocrinology texts even went so far to call T4 a “pro-hormone” because it needs to be changed into T3 to work in the cells. So, sometimes even though our T4 levels can look reasonable, the T3 levels can be elevated, creating some havoc. According to my “A Manual of Laboratory and Diagnostic Tests”, the Free Triiodothyronine T3 (FT3) test is “one of the determinations used to evaluate thyroid function and measure that fraction of the circulatory T3 that exists in the free state in the blood, unbound to protein. It is done to rule out T3 toxicosis, hypothyroidism, and hyperthyroidism; to determine thyroid status;l and to evaluate thyroid replacement therapy.”

                  Post count: 93172

                  There is a form of Graves where the patient can have a T4 or T3 that is pretty okay on paper, yet it is converted very rapidly to free T3 in the body… that was the case with me and the free T3 that can really mess you up. My T3 and T4 were high normal on my first test, but the doctor knew better and ordered free T3… sure enough, it was outta the ballpark.


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