Thyroid UK
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T3 Result

Finally got T3 tested and result was 4.7 (4-7), so I gather the result is in range but not hugely so. When I started on T4 it brought me back into "normal" range for TSH / T4 levels within 6 weeks but T3 never tested till now, so I'm thinking my T3 levels must not have been that great in the 2 years since diagnosis / starting Thyroxine. So my question is does it take longer for T3 levels to respond to Thyroxine than TSH and T4 levels if that makes sense?

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Hi Syd35. Is that an FT3 test or a Total T3 Test? I'm guessing from the range it's FT3?

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Oh gosh sorry to sound dumb but I really don't know for sure I'll check at my GP follow up tomorrow!

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No, it doesn’t take longer for T3 levels to respond to Thyroxine than TSH and T4 levels. Looking at the results you posted recently healthunlocked.com/thyroidu... your body is capable of doing a reasonable job of converting T4 to T3, so I’d suggest you ask for an increase in levo dose, as there’s room for improvement with an FT4 of 18 in a range that goes up to 25.

You may not need T3, just a raise in levo.

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I'm pretty sure that based on the lab ranges, it's Free T3. FT3 is the correct test, Total T3 or T4 tests are not because they are a mix of two types of T3 or T4 = inconclusive. If it is FT3, your FT3 is non-existant. This means you are not converting T4 into T3. The good news is that it can easily be fixed. That's unfortunate that your doctor had you on T4 supplementation for two whole years, but failed to ever testing your FT3. After two years on only T4, I'm sorry, but your T3 is never going to catch up and become adequate levels by taking T4 alone. It would have improved by now.

A big question: Why are you not converting T4 into T3? One of the most common causes is thyroid antibodies interfering with the T4/T3 conversion. Did your doctor ever test your thyroid antibodies, TGab and TGab? These need to be tested to know if you have autoimmune disease Hashimoto's causing your thyroid disease.

Another question: Do you have a goiter or swelling in your thyroid area?

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T3 has a very short half life and is fast acting. T4 is the opposite. Your FT3 is so low that even if you increase T4 dosage, your FT3 will probably never get to where it should be all by itself. Increasing T4 will also increase your T4 levels. If they are up where they should be, adding more might make your T4 too high, whereas your T3 still lags behind. Since you don't convert, supplementing T3 is the only way to get your T3 up where it should be.

What are your TSH and FT4 levels and ranges? OK. I found them in your other post that Jazzw linked.

T4 - 18 (10-25)

T3 - 4.7 (4-7)

TSH - 0.68 (0.55 - 4.78)

You are definitely not anywhere near converting T4 to T3. Your FT4 is right where is should be at over 1/2 range. Yours is 18 and half range is 17.5. The more T4 you add, the higher your T4 will go. If it gets up near 21.25 (3/4 range), it's getting close to being too high in the range.

Your FT3 is bottom barrel, 4.7. No wonder you have a bunch of symptoms! The target part of the range for FT3 is over half range (5.5) but closer to 3/4 range (6.25). You are a very long ways from being at even half range.

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Thanks for taking the time to reply it's all so complex isn't it. Yes I have confirmed hashi's. Going to GP today so have a lot to discuss with him!

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T4 - 18 (10-25) T3 - 4.7 (4-7)

Were these to tests done at the same time? If not, anything that's been said about your capacities to convert are just conjecture. Your FT4 level could have changed in the interim. They really do need to be done at the same time. :)

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Hi GG, yes both tests done at same time the other week. So now I'm really confused with some upthread advising I might have a conversion issue and then some saying I seem to convert ok. So what does your wise young self think before I go to GP later demanding T3 not that I'll probably get my way lol.

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You most definitely have a conversion problem. Your FT4 is mid-range, but your FT3 is right down the bottom of the range. They should be more less an equal distance through the range. So, as your FT4 is just over mid-range, your FT3 should be just under mid-range.

Most people need their FT3 right up the top of the range to feel well. Which means you would have to have your FT4 well over the top of the range to get your FT3 up the top. But, when your FT4 get up to the top, you start converting more to rT3 than to T3, so your conversion rate T4 to T3 drops. So, it will never catch up with itself. So, my opinion is that you need T3 added.

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Thanks GG, I posted a new thread today that my GP has agreed to a trial of T3, so we shall see...

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You're welcome. :)

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