Thyroid UK
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DIO2 and T3, it's very probable you don't have a gene defect, just a lack of T2 see below!

Ok here's a very important reason you need your FT3 checked, you need to know if your converting FT4 to FT3 reason is some people have problems as they say making FT3 they can blame it on a made up gene defect called DIO2, 

Now read this to understand the no defect in the genes, yes you may not be able to make FT3. You see that DIO2. Here's why there are in natural Dessicated thyroid hormone (NDT) not just T3-4 but T1-2-3-4 and Calcetonin, now T2 is needed to make Deiodinase this is needed to remove an iodine molecule from T4 to make T3, I believe they know how look at the gene number DIO2 and Deiodinase, and T2, do you believe in coincidences? In this case people in this situation need NDT natural thyroid... 

I'm not medically trained but I read a lot, and I like to know the why, not just the fact of what is... Hope that helps 

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rrg - I found your post difficult to understand - please read it through and see what you think.  I realise you have something important to say but it doesn't really make sense - or is it me ??


Hi Marz ok people that cannot make T3 yet have plenty of T4 the specialists say you have a gene defect, the gene is called DIO2. Low or no deidonase.

The thyroid hormone needed to make Deiodinase is T2, 

Deidonase is needed to remove an iodine molecule from the T4 =4 iodine molecules to make the energy hormone T3=3 iodine molecules, 

So if T2 is needed to make this enzyme deidonase it suggests to me there's no defect in a gene just a lack of T2 

To me the solution is NDT, that has T2 in it, plus T2 is needed for brain energy, whereas T1 is for smooth muscles, or you can take T3. 

Hope that clarifies it for you... 


Gene defects can be tested for. They aren't a figment of people's imagination. So people who've had the testing can be sure whether or not they have the gene defect.


DIO2 is just one gene.

So far, we are at the edges of the ocean of understanding genes. No-one knows what else will be identified - DIO2 may end up being just one of many genetic influences.

I'd also like Roadrunnergreg to tell us how much T2 and T1 are in desiccated thyroid?

My belief is that there might be detectable levels of T2 and T1 in desiccated thyroid - but at a very low level. In agreement with diogenes that most T2 is produced outside the thyroid. I am also convinced that at least some people have got confused - thinking of T1 as being MIT and T2 as DIT. Or MIT as being T1 and DIT as T2.

monoiodotyrosine (MIT)

diiodotyrosine (DIT)


But if you don't make enough T3, there won't be enough T3 to be deiondinased to enough T2, so the effect would be the same - not enough T3 = not enough T2 (and therefore not enough T1 either). So a vicious circle. But I'm probably confused ;-)


You took the words out of my mouth! :D


Actually, they are iodine atoms, not molécules. :)


Always interesting always knowledgable thank you x


Actually the vast bulk of T2 is produced in the body from T3 and rT3, not in the thyroid so much. This indicates that T2 production is adequate from either T4 mono therapy, combined T3/T4 therapy or T3 alone. Any T2 present in NDT shouldn't have much additional effect.

J Clin Invest. 1978 May;61(5):1276-85.

3,3'-Diiodothyronine production, a major pathway of peripheral iodothyronine metabolism in man.

Gavin LA, Hammond ME, Castle JN, Cavalieri RR.


That's what I was thinking. So glad you confirmed it. :)

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I wonder if you are confusing T2 with D2.  D2 is type-2 deiodinase whose expression is a consequence of the DIO2 gene.  The DIO2 polymorphisms (minor defects) lead to slightly less D2 activity which can cause minor cognitive problems in patients on levothyroxine only treatment.

Everyone can convert T4 to T3, otherwise they would be dead.  Some people have impaired conversion, or need higher than normal thyroid hormone levels, in which case they will need T3 medication.  They may also require a little T3 if their thyroid is damaged or removed, in order to replace the T3 the normal thyroid would produce.

The pituitary relies on D2.  So if there was any general problem with making D2 (such as a selenium deficit) the pituitary would have impaired D2 and the TSH would go very high.


Thanks for your replies, but here's some info on T2 etc 

To convert T4 into T3 (and T3 into T2), your tissues use an enzyme, deiodinase, to knock one of the iodine molecules off. Well, some of your tissues require a supply of T2 in order to make this enzyme (while other tissues are able to make deiodinase without T2). (This indicates that T3 only therapy does not result in the body being able to convert T3 to adequate levels of T2, T1, and T0 at least not in all tissues. Other research also indicates this. There are several enzyme pathways for thyroid hormone conversion and various tissues and organs will have more or less of certain ones. All T3 therapy depresses one major pathway and does not affect others. There is no way to guarantee that a person on all T3 therapy would be able to get adequate T2 and other hormones to be truly healthy.)

(note that some doctors use Pregnenalone, as in their findings, it has the ability to open up hormonal pathways.) hence my belief right or wrong DIO2 isn't a gene defect, but T2 Deidonase problem in some tissues. 

T2 is taken up by the cells and acts directly on the mitochondria. The T2 is used to produce ATP. ATP is the fuel for our cells; it is the energy our cells use to function. So you see, T2 is absolutely vital for the cells to function. Yes, it is true that a healthy thyroid gland does not make very much T2. But certain cells in the body depend on it.

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Well I had the test done 6 years ago when it really was in its infant stages ... I have got the double faulty gene .. I thought I was dying slowly on t4 as I got worse on the one tablet fits all .. Now on a combination of t4 100mcg and T3 80 mcg daily ... So trust me it's not a made up test as I have none of the symptoms now and only got 8lbs in weight to loose to get back to my normal weight after putting on 3 stone


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