Thyroid UK
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DIO2 test with normal thyroid function

Dear members,

Can someone please explain whether it is worth running the DIO2 test if thyroid function is completely normal ( T4, fT4, T3, fT3, TPO, TSH, TgA : all mid normal range ; not even suggestion of inadequate function ?)

I expected at least the 3s to be low or antibodies ( sub clinical Hashimoto) high as my aunt is severely ill ( neurological signs plus chronic allergies; asthma liver problem) but even they are normal .

Can there be a positive DIO2 test for polymorphism even with normal thyroid results please ?

Thank you very much in advance


4 Replies


DIO2 gene testing is not confined to showing impairment of T4 to T3 conversion and as you're not taking Levothyroxine you don't need to know whether you have the impairment so I would save your money.


Yes the point of DIO2 gene variation is that test results for FT3 can look fine, but we remain hypothyroid

Can you add results and ranges

What a GP says is adequate dose of Levothyroxine very often is not

For full Thyroid evaluation yoyr Aunt needs TSH, FT4, TT4, FT3 plus TPO and TG thyroid antibodies. Plus vitamin D, folate, ferritin and B12.

Essential to test thyroid antibodies, FT3 and FT4 plus vitamins

With Hashimoto's we can have poor conversion and or low vitamins

Private tests are available. NHS often refuses to test FT3 or antibodies

Medichecks Thyroid plus ultra vitamin or Blue Horizon Thyroid plus eleven are the most popular choice. DIY finger prick test or option to pay extra for private blood draw. Both companies often have money off offers.

All thyroid tests should ideally be done as early as possible in morning and fasting and don't take Levo in the 24 hours prior to test, and T3 12 hours prior to test, delay and take straight after. This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip, GP will be unaware)

If antibodies are high this is Hashimoto's, (also known by medics here in UK more commonly as autoimmune thyroid disease).

About 90% of all hypothyroidism in Uk is due to Hashimoto's

Is your Aunt on strictly gluten free diet?

Hashimoto's affects the gut and leads to low stomach acid and then low vitamin levels

Low vitamin levels affect Thyroid hormone working

Poor gut function can lead leaky gut (literally holes in gut wall) this can cause food intolerances. Most common by far is gluten

According to Izabella Wentz the Thyroid Pharmacist approx 5% with Hashimoto's are coeliac, but over 80% find gluten free diet helps significantly. Either due to direct gluten intolerance (no test available) or due to leaky gut and gluten causing molecular mimicry (see Amy Myers link)

But don't be surprised that GP or endo never mention gut, gluten or low vitamins. Hashimoto's is very poorly understood

Changing to a strictly gluten free diet may help reduce symptoms, help gut heal and slowly lower TPO antibodies

Ideally ask GP for coeliac blood test first


Thank you so much for your reply , we are desperately trying to help my aunt especially with her neurological issues and will not survive it for long - already may need to placed on oxygen therapy to help her breath .

I can post her results tonight when I get them by email ( they were only read out to me )

His interesting study tempted me to test her thyroid as it was the only thing which hasn’t been done so far :

Not that I wish anything bad for her but was at least feeling positive that we may find something treatable - but I was shocked to find even her 3s normal despite her poor condition

rT3 is not available to test in Slovakia ( where my aunti lives ) and not sure about the other vitamin deficiencies ; not antibodies against T3 and T4 : with regards to these - if positive - would they falsely elevate the T4 and T3 levels ? What about fT4 and fT3 ? If necessary I can try to order the home test kits for her and get it tested here in U.K.


Hydrous results for my aunt :

T4 103 nmol/l (60-165)

FT4 17.5 pmol/l (11-25)

T3 1.4 nmol/l (1.04 - 2.5)

FT3 4.19 pmol/l ( 2.5 - 5.8)

TSH 2.3 mlU/l ( 0.17 - 4.05)

TPO < 7 IU/ml ( < 25)

TgA < 10 IU/ml ( < 60)

Should any action be taken ? She is so ill I can’t actually believe her results look so good ! And she takes also so many nasty medications too ; but nothing is helping ! For high blood pressure , depression , neurological problems - she is almost on ventilator; totally unable to do anything on her own with her tetraparesis ; liver problems , allergies etc ( no gluten intolerance )

She does take some vitamins

Doctors are baffled ; would it be worth it to suggest T3 supplement ?

Her DIO2 test will have results in few weeks ; if anything is found - is it worth it then to supplement with T3 ?

Thank you for all the help


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