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Thyroid UK
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I've heard that as I'm a poor converter of T4 then I will always have problems with thyroid replacement and with whatever replacement I choose. Is that correct?

Also my cortisol test isn't a proper test as it only shows total cortisol and not free cortisol and for that I would need a saliva test. Is this true?

My head is now spinning.

Could someone reassure me that this isn't right.

9 Replies

Your right the doctor is wrong. If you take T3 only, it doesn't need to be converted as it is the Active hormone required by our receptor cells. If we don't convert T4 then we do have problems as it is a pro-hormone supposed to convert to sufficient T3 but sometimes it doesn't.

You could always take NDT too, as it is a natural product and might be able to convert the T4 in it but of course it contains T3 anyway.


Shaws, thank you for getting back to me, its put my mind at rest. I need it!


When we are trying to recover our health by ourselves, our head can spin with so much information. We cannot take it in at first.


Mischa, when you have a problem converting Levothyroxine (T4) to T3 the addition of some T3 or the T3 in NDT overcomes the conversion issue. The addition of T3 or switching to NDT can also stimulate better conversion of T4 to T3.

I'm not very au fait with Cortisol testing but members recommend saliva testing 4 x throughout the day is more revealing of issues than the cortisol blood test which will show low or high morning cortisol.


thank you Clutter. I'm arranging to have a saliva test.

Does this mean that if I was considering NDT I shouldn't start taking it until after the test?


Mischa, no NDT won't affect the cortisol saliva test.


I improved my conversion rate when I improved my vitamin and mineral levels. I'm still not good enough at converting though, and felt poisoned when I took anything containing T4, so I now use T3 only.


I do take all the right supplements - iron is good and so is Vit D and calcium. I'm going to take a B12 test.

Humanbean, I'm torn between the T3 which I will take with T4 or NDT. To be honest, after being on it for nearly three years, I'm really not a lover of T4 but I'm not confident of going T3 only at this moment.

Do you know why you're not converting well? Have you done the saliva test?

It's so complicated and never-ending. When you think you've fixed one thing then something else pops up and surprises you and demolishes that idea. And you land in new territory which can be quite scary.


I don't know why I don't convert particularly well. I have wondered about getting the DIO2 gene test. But it isn't high on my list of priorities at the moment. While I can still choose to treat my thyroid how I want to it doesn't really matter if I have a faulty gene. If it ever becomes impossible to self-medicate then I will take the gene test in the hope of getting T3 from a doctor.

I've done the adrenal stress profile twice, separated by a year, and it showed high cortisol both times. I was under lots of physical and physiological stress both times as a result of non-thyroidal illness and chronic pain. I still have the pain but some other issues have been fixed. I don't have such chronic insomnia at the moment so I'm guessing my cortisol is now lower than it was.

I've tried NDT and didn't get on with it terribly well. I didn't feel desperately bad, but I didn't feel good either. On T3 I definitely feel better, particularly since I've had some time getting used to it. And I like it too. I can adjust my dose far more easily than I can with anything containing T4. If I have a particularly busy day I can take an extra crumb of T3 to give me the extra energy I need. If the next day reverts back to being an ordinary day I just take my basic dose again.


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