# T3 vs. T4?



## nikkij0814 (Jul 13, 2011)

What's the difference between taking T3 vs. T4 medication? I'm currently on Synthroid...


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## joplin1975 (Jul 21, 2011)

So you are on T4 meds now.

With T4 meds (well, and for those who have a functioning endocrine system!), the liver converts T4 into the active hormone, T3, as you need it.

With T3 meds, you are getting the straight active hormone, which has a much shorter half life and can't as easily be stored.

The combination meds have T4 and T3.


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## Andros (Aug 26, 2009)

nikkij0814 said:


> What's the difference between taking T3 vs. T4 medication? I'm currently on Synthroid...


Are you doing well on the Synthroid? T3 is the active hormone from whence comes your energy, cognition and healing.

Joplin explained the process very well.

If you are not feeling good; please furnish info such as how much Synthroid and current TSH, FREE T3 and FREE T4 labswith the ranges.


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## nikkij0814 (Jul 13, 2011)

[quote name='Andros']Are you doing well on the Synthroid? T3 is the active hormone from whence comes your energy, cognition and healing.

Joplin explained the process very well.

If you are not feeling good; please furnish info such as how much Synthroid and current TSH, FREE T3 and FREE T4 labswith the ranges.[/U]

3/1, Felt great! Everything fine, no emotional upsets, things stable... had been on 175 Levothyroxine for 12 weeks:
TSH 2.07 (.4-4.5)
T3 uptake 31 (22-35)
T4 10.2 (4.5-12.0)
Free T4 3.2 (1.4-3.8)
[Endo told me to come back in a year, I felt fine]

3/26, crying, anxious, etc. after on 175mcg Levothyroxine for 15 weeks; endo told me that it couldn't be my thyroid, and I got the below test results from my PCP. Once I faxed these results to the endo, he said to lower my dose:
TSH 0.775 (.4-4.5)
T4 12.8 (4.5-12.0)
[Decreased dose to 162mcg Levothyroxine after this test result]

On 5/21, crying, anxious, etc., after on 162mcg Levothyroxine for 8 weeks:
TSH 0.23 (.4-4.5)
T4 10.3 (4.5-12.0)
T3 uptake 35 (24-39)
Free Thyroxine Index 3.6 (1.2-4.9)
[Decreased dose to 150 mcg name brand Synthroid after this test result]

I had my labs drawn on Thursday, 6/21, on 150mcg Synthroid for only 4 weeks:
TSH 1.9 (0.4-4.5) -- the nurse called with this number -- I'll get the full info on Monday at my appointment.

Still having exhaustion in the afternoons, and feel tearful easily. I will have some crying spells and feel "on edge" or anxious as well, though it is episodic and not all the time. Oddly, I feel perfectly fine in the mornings.

Something else I notice when looking at this is that the ranges for T3 uptake are different between the lab results of the Endo and my PCP.

I'm worried that my levels will continue to adjust, and that my TSH will likely continue to rise because I have only been on 150mcg for 4 weeks now. Could this be the reason behind my continued crying spells? I do know (now) that I obviously continue to adjust to med changes longer than even the 12 week mark.


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## nikkij0814 (Jul 13, 2011)

Do the above-listed results show that my body is indeed converting T4 to T3, given that my T3 uptake numbers are on the high side of the "normal" ranges?


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## JPGreco (Mar 2, 2012)

Well if the ranges are different that means your PCP and endo use different labs, which means the tests are in different concentrations (micro international units, milli international units, international units, etc, etc) over varying concentrations (deciliter, militer, etc). In order to compare on lab to another you need to do some conversions.
Usually you can get an idea of the conversion by comparing labs.
In my case I had one that was 3.xx over something. Another lab it was 3xx (no decimal). I realized for that particular test, I had to move the decimal between the two labs and that allowed me to adjust other tests easily. Yay math...
However, even with all that as long as you are in range on any lab it gives you an idea of where you are on any comparison lab. That is if you understand that using percentages.


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## Andros (Aug 26, 2009)

nikkij0814 said:


> Andros said:
> 
> 
> > Are you doing well on the Synthroid? T3 is the active hormone from whence comes your energy, cognition and healing.
> ...


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