DIO2 (Deiodinase 2 Gene) test: Hi Quick question... - Thyroid UK

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DIO2 (Deiodinase 2 Gene) test

Rennixon profile image


Quick question. -should I have this test? As there is the possibility that hypothyroidism is inherited is it worth the money?

Back story : I was diagnosed with hypothyroidism 15years ago & at roughly the same time so was my mother. She was also found to have type 2 diabetes. Looking back I think my mum had low thyroid for years before & I also think my grandmother had it too. I have battled all my life with bad stomachs, headaches, pmt, heavy/no periods, pocs, low fertility, tiredness, etc, etc you get the picture. Many of my mums family are on the big side and have type 2 diabetes. Recently my older sister has been diagnosed with hypothyroidism too.

25 Replies

I had the test recently and it came back positive

Hi Charlotte,

Did you have low FT3 or was it something else that made you have the test?


I was on 150mg of levo and still feeling awful, weight gain, hair loss you know all the symptoms, most of the women in my family have thyroid issues.

Started off with FT3 tests came back extremely low then went on to the genetic testings, I don't convert from t4 to t4 or produce any t3

Hi - the DIo2 gene is to do with conversion from t4 to t3 in the body, rather than just an inherited tendency to thyroid problems. You certainly don't need to know if you have a flaw in it to treat any thyroid problems. You really don't need to know the reason for bad conversion, just to recognise if you are a bad converter - easy to see in numbers - and treat accordingly.


Hi Gillian

My FT3 has gone down in the range, but I have not felt well on T4 treatment since I started it. My go has now decided I need to lower my T4! I'm going to jump through the hoops at the moment (another story) I have been looking back at my test results & how I've felt & wondered if this is the reason. So trying really to justify the cost if that makes sense?

I personally would be inclined not to bother with the test and would spend the money on some nutrient tests and t3 instead. Possibly also some good supplements if tests show you need them. I don't think that finding you might have a particular reason for bad conversion is going to add anything much to the picture, beyond maybe a bit of interest.


Thanks Gillian, I take all the supplements etc, my iron is the lowest, which seems to be an ongoing thing. My T3 has fallen but not bottomed out.

I do not agree with that statement startagaingirl

I felt dreadful on T4 only for 14 years, then got T3 prescribed by a private doc. Made me feel human again. Since then I've battled with GPs and endos to keep prescribing T3. I got the DIO2 test earlier this year, it came back as faulty thyroid gene from one parent. That confirmed all my gut feelings over decades, ie that I was not a classic hypo patient. I shoved a copy in front of an endo recently and she was unable to argue with me. It is DEFINITELY worth getting.

Rennixon profile image
Rennixon in reply to marigold22

Thanks, I too have felt ill all the time. I've had to cut my hours at work to 2 days. I can't work them together either or I'm exhausted for the next 3 days. I've just had a really busy period of time ( i.e. Going out all day for two days running) & then had palpitations anxiety attacks & feeling sooooo tired, I end up in bed for days. I'm 51 going on 80! How can I be normal? My friends hold down full time jobs,do all their own housework, & go out every weekend. I simply can't do all this & it makes me so angry.

But that doesn't mean that you need a gene test to know that you should add t3, you already know that.

If your iron is an on going problem, have you looked at addressing any absorption issues with may be Apple cider vinegar and a gluten free diet?

Yep I am gf & take basically everything recommended.

Your correct I should buy some & stop procrastinating haha!

By the way, if the DIO2 test was free, every single person diagnosed with hypothyroid would probably be tested. As it is, we have to pay around £160 for it.


I didn't need a DIO2 test to tell me conversion is poor. I could see that myself because FT3 was below range when TSH was suppressed and FT4 in the upper range.

Some people have been able to persuade endos that because they have some impairment of DIO2 that they should be prescribed T3 in addition to Levothyroxine but it made no difference to many people in areas where T3 is already banned.

Rennixon profile image
Rennixon in reply to Clutter

Interesting Clutter, that ppl didn't get the T3 prescribed. In my area it's not prescribed & it's hard to change doctors too. It's expensive to go private though. Ugh!!!

You don't need to go private and chances are they wouldn't prescribe anyway as they are generally just nhs trained doctors doing extra work. Also any prescription a private doctor issues has to be paid For, though you can then source from Europe. Alternatively just self-treat as many of us already do.

Going to do a separate post to ask for recommendations for T3. If you have a reliable supplier would you pm me please


Clutter profile image
Clutter in reply to Rennixon


I'm not sure why people place so much store on the DIO2 test. Low TSH, high FT4 and low FT3 demonstrates poor conversion. NHS England are trying to de-prescribe T3 from NHS so its not worth changing doctor in the hope of getting it prescribed. Private prescription is expensive unless you source German or French T3, but you can obtain T3 without prescription. If you want to self medicate write a post asking members to send you PMs where to source T3.

marigold22 profile image
marigold22 in reply to Clutter

We do the DIO2 test so we know for absolute certain that it's genetic and not something we have done. Plus it is additional clout if needed.

Clutter profile image
Clutter in reply to marigold22


In what way is it additional clout?

marigold22 profile image
marigold22 in reply to Clutter

Clutter - when one has been ill with hypo for 35 years, lost everything over those years, nearly losing custody of my son even, wondering if it's my hypothalamus, my pituitary, because I've been so incredibly undermedicated for 34 of those 35 years, it is proof in black & white what is actually wrong with me.

Very understandable marigold22 that proof in black and white validates our years of knowing something is not right in our own bodies. I understand you totally, wishing you health.

SlowDragon profile image
SlowDragonAdministrator in reply to marigold22

I would agree totally that it's worth doing

My GP and endo both took the whole thing much more seriously with positive DIO2 test result

We all have different journeys x

It’s definitely worth getting done. I have the DI02 conversion problem and showing my doctor the test results was instrumental in me being prescribed Liothyronine, which has given me my life back.

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