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  • Anonymous
      Post count: 93172

      Bobbi,
      After you told me that T-7 was a calculation based on T3 and T4, I worked out from a couple of my labwork results that it is (T3 + T4) divided by 100. Thanks for being our resident lab expert and always being willing to share information!

      Anonymous
        Post count: 93172

        Does anyone know in the thryoid profile, what the T7 measures? Why would this measurement be slightly out of range (high) while the rest are well within normal?

        Anonymous
          Post count: 93172

          YEARS ago, it was thought that the T3 + T4 = T7, was the best test to measure hormone levels. It is now known that the ‘ free T3 ‘ and the ‘ free T4 ‘ are much more accurate indications of thyroid function. Geez! I haven’t heard that term ” T 7 ” in a very long time!! Are you seeing an Endocrinologist?

          Anonymous
            Post count: 93172

            Try running a search for the term, because I remember researching an answer to this question in the past. I am at my summer home right now, and do not have my reference materials handy. But I believe I remember something about T7 being an arithmetic calculation based on the T3 and T4 levels. Perhaps a ratio? Anyway, try the search, because if I found it, I would have had the book in hand when I typed the post.

            Bobbi — NGDF Asst. Online Facilitator

            Anonymous
              Post count: 93172

              Haditonce, to make your search easier I just happen to have that post saved in my personal Graves’ folder…

              Re: T-7 ???
              Posted by : Bobbi on 02/21/99 at 08:01:05

              T7 is also known as the “free thyroxine index” or FTI on some tests. They get the “7” because the number they come up with for this is based on a mathematical calculation of the T4 value and the T3 uptake ratio (3 plus 4 equals 7, I guess). The reason for looking at this value is this: the total amount of T3 and T4 is not a complete indicator of how hyper or hypo we are, because most of the thyroid hormones are bound up by proteins and are not “active”. It is only the “free” thyroid hormone that the cells use for metabolism. So this test tries to correct for the amount of thyroxine-binding globulin (TBG) present in the blood. From A MANUAL OF LABORATORY AND DIAGNOSTIC TESTS, fifth edition, page 428: “This index is a mathematical calculation used to correct the estimated total thyroxine (T4) for the amount of thyroxine-binding globulin (TBG) present. To perform this calculation, two results are needed (from other tests): the T3 value and the T3 uptake ratio. The product of these two members is the free thryoxine index (FTI). The FTI is useful in the diagnosis of hyper- and hypothyroidism, especially in patients with known or suspected abnormalities in thyroxine-binding protein levels. In such patients, blood levels and clinical signs may seem contradictory unless both T4 and TBG are considered as interrelated parameters of thyroid status. Measurement of the free T4 also gives a more accurate picture of the thyroid status when the TBG is abnormal in pregnant women or in those persons who are being treated with estrogen, androgens, phenytoin, or salicylates.”

              The calculation is this: FTI = T4 total x T3uptake(%)/100.

              “The free thyroxine index permits meaningful interpretation by balancing out most nonthyroidal factors.”

              Hope this is clear,
              Bobbi

              Free T4 Index, or T7, is a mathematical calculation derived by multiplying the T4 X T3 resin uptake that is done in order to evaluate thyroid function.

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