Thyroid peroxidase antibodies and T4/T3 Conversion - Thyroid UK

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Thyroid peroxidase antibodies and T4/T3 Conversion

whatevs profile image

I was checking out mymedichecks results earlier and took a look at the info for Thyroid peroxidase antibodies and it mentions the following:

Thyroid peroxidase is an enzyme which is produced in the thyroid gland and is important for converting T4 to the biologically active T3. This test looks for antibodies to thyroid peroxidase which indicates that the body's immune system is attacking the thyroid gland and impairing its function

I have a problem with conversion and now take both T4 and T3 but I never knew the cause. Could high levels of the above be the reason why I don't do well on T4 alone ? If my antibodies are high on my current treatment should I perhaps try lowering T4 further and upping T3 ?

11 Replies
SlowDragon profile image

High TPO antibodies confirms you have Hashimoto's also called autoimmune thyroid disease

Low vitamin levels are extremely common especially with Hashimoto's

Yes Hashimoto's can hinder conversion, but getting vitamins optimal is often very helpful in improving conversion

Have you had vitamin D, folate, ferritin and B12 tested? Can you add your most recent blood test results

Couldn't see any vitamin test results on your profile or posts

As you have Hashimoto's Are you on strictly gluten free diet?

Poor gut function with Hashimoto's can lead leaky gut (literally holes in gut wall) this can cause food intolerances. Most common by far is gluten. Dairy is second most common.

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

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 or buy test online for under £20, just to rule it out first

Assuming test is negative you can immediately go on strictly gluten free diet

(If test is positive you will need to remain on high gluten diet until endoscopy, maximum 6 weeks wait officially)

Trying gluten free diet for 3-6 months. If no noticeable improvement then reintroduce gluten and see if symptoms get worse

Have you had your ferritin, folate, b12 and vit D tested recently, and if necessary supplemented to optimal, upper half of ranges? Low vits/ mins can hinder T4 conversion, and needed anyway for good thyroid health.

This is a surprise. The deiodinase enzymes convert T4 to T3 etc. I always thought TPO is about making thyroid hormone but perhaps it has a role in T4 to T3 conversion within the thyroid gland. We know that patients who lose their thyroid miss out on the deidinase activity in the thyroid. I wouldn't expect TPO to have an impact outside the thyroid.

Perhaps @diogenes could advise us.

Marz profile image
Marz in reply to jimh111

diogenes - Jim - something went wrong with your tag so have re-done it. 😊

jimh111 profile image
jimh111 in reply to Marz

Thank-you. Just experimented, if I just type @diogenes it doesn't work! I have to type and then select from the list.

Marz profile image
Marz in reply to jimh111

Spot on !

diogenes profile image
diogenes in reply to jimh111

I believe TPO is locally involved in converting some of the T4 in the thyroid gland into T3 that is secreted directly into the bloodstream. Antibodies destroying this will only affect this local activity not corporeal conversion. But it could be that the reduced or even absent direct thyroid conversion cannot always be made up for by the body's own conversion process. Hence the need for T3 therapy in such a case.

I think "important for converting T4 to the biologically active T3" is not intended to mean that it has a role at the actual conversion process at the cellular level. It's perhaps speaking of the function of the thyroid gland as a system that does produce about 20% of T3. The rest of the T3 conversion happens at the cellular level througout your body.

Werner & Ingbar's Thyroid, a medical textbook, devotes chapter 8 to Genomic and Non Genomic Actions of Thyroid Hormones, T3 and T4, (TH). The book explains how the nucleus of each cell contains TH receptors and most of our biologic effects at cellular level are mediated by TH receptors. Further, TH acts at nongenomic sites, such as plasma membrane, cytoplasm, and within our mitochondria. The mitochondria are the little power generation facilities within almost all cells in the body.

Your body uses TH at the genomic level through two kinds of Deiodinase proteins, DIO1 and DIO2. In healthy people, the DIO2 pathway is believed to contribute more to plasma T3 than does DIO1. Plasma is what they're measuring when they try to determine what's going on and whether your hormone treatment is working.

According to the text, the presence of T3 hormone stimulates DIO1 expression (operating principally in liver and kidneys), while T4 levels modulate DIO2 gene expression through local deactivation or activation of ubiquitination/deubiquitination processes. In skeletal muscles, the brain, pituitary, and brown fat, high T4 causes ubiquitin to attach to the DIO2 protein, degrading it, and reducing DIO2 activity. The reverse process occurs with low T4, permitting tissues that contain D2 to modulate T3 concentrations at the local level. This is how we can drag around the house all day to weak to do anything, or feel energized, as a result of TH action. Too much TH can have the same effects as too little.

Conversion problems are known to be due to genetic variations that alter the ratio of T3 and rT3 produced during deiodination. There are DIO1 genetic variations that influence conversion, as well as well-known DIO2 variants.

jimh111 profile image
jimh111 in reply to RockyPath

This was my understanding that the deiodinase enzymes D1, D2 and D3 regulate T4 to T3 conversion. It may be that TPO determines how much T3, T4 the thyroid produces but it is misleading to say it 'is important for converting T4 to the biologically active T3'. This would give the false impression that TPO controls peripheral T4 to T3 conversion, especially if the thyroid has been removed. However, I know nothing about TPO.

NWA6 profile image
NWA6 in reply to jimh111

Unless it IS important and we just don’t know enough yet??

RockyPath profile image
RockyPath in reply to NWA6

Almost every member of the Animal Kingdom relies on a thyroid gland for energy production, so huge numbers of researchers around the planet have been studying thyroid hormone processes using rats, salmon, snails, what have you, for over 50 years. It's likely that if there were a connection beyond TPO's action messing up the physiology of the thyroid gland, and the gland's ability to do conversion within its specialized cells and shoot out T3 to the bloodstream, somebody would have noticed it by now.

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