Does RAI worsen T4 to T3 conversion?

I had Graves, then RAI in 1990, then hypo and on Levo, mostly 175mcg. Something changed in 2014, and I became very very ill. T4 at top of range, T3 at the bottom. I started T3 in 2016, and wow my life came back. Does anyone know how much RAI affects T4 to T3 conversion? The Endo told me at the time of my RAI that it would only destroy some of my thyroid, but they'd err on the side of making me hypo instead, as that's easy to treat...Yes, right!! So I don't know how much was destroyed. I was relatively ok on 175 Levo for 24 years; them wham, immense weakness etc etc - all the hypo symptoms. So what would provoke the change after 24 years? Does RAI ultimately affect conversion?

29 Replies


Being thyroidless reduces conversion because you lose thyroidal conversion and rely on periopheral conversion only. This would affect you shortly after RAI not 24 years later.

Menopause seems to sometimes disrupt previous satisfactory levels.

Have you had your thyroid levels checked recently to see whether 175mcg is adequate dose?

It sound as if you've built up reverse t3 so no active hormone can reach the cells that need it. Or it could be low ferritin or B12. As we age these levels can decline.

I cannot answer your question re RAI and conversion. What I would say - I don't know how people who have had RAI can possibly feel well on levothyroxine alone. I am sure people with no thyroid gland or producing any thyroid hormones can recover on T4 only. T4 - levothyroxine - is inactive and has to convert to T3 (liothyronine). I would ask for some T3 to be added to your T4.

Shaws people who have had RAI can do perfectly well on Levo alone, I do 😊

I am hypothyroid and am perfectly unwell on levothyroxine. I cannot take it at all.

So T3 has saved my life and my husband's and family. Thanks to

We are all very different and what one suits one person does not suit another and research has shown that most benefit with a combination of T4/T3.

Of course we are all different that is why we can't assume that people who have no thyroid can't function without T3.

Levo doesn't work for my husband, he needs T3 so I'm well aware of the differences in treatment.

Shaws We've all asked for t3. It's been refused 😢

That is so disappointing that they are very unaware of the beneficial affects for many people. The saying goes 'ignorance is bliss' but not when it comes to dispensing thyroid hormones which make patients well.

If your NHS endocrinologist recommends you have T3 you should be prescribed it.

Look up your local CCG guidelines on Liothyronine

My local CCG guidelines state

"The use of liothyronine in the treatment of primary hypothyroidism should be initiated followed specialist review in secondary care. This should be reviewed at three months and only continued if there is improvement in symptoms. In this scenario, a joint management plan should be agreed with the patient’s GP for ongoing prescription."

I've written to my ccg 2x got 2x patronising replys! They are not budging. Seeing my MP in sept.

Could be low vitamins.

low vitamin D, folate, ferritin or B12 all affect thyroid. As we age often stomach acid reduces, leading to less nutrients from food.

I believe what happens with Graves and even surgury but def RAI is the receptors are damsged and a form of central or tertiary hypo occurs and whilst t3 will work for some only NDT works for many also far higher does and a totally non existant TSH is vital to acheive a quality of life thats the experience of my husband

Thanks RFU123. I am learning all the time. I assumed RAI made people hypothroid.

It does!

thats what they like to tell you but they ignore the damage to thyroid hormone receptors

Which I think would be one of the most important revelations and should have been/should be investigated otherwise it's a waste of time and patient's energy.

Reallyfedup123, interesting analysis! My experience supports it. I had a thyroidectomy and RAI for cancer, have had a long road the past 4 years in bed most of the time. I'm currently starting to get my life back, am self medicating on NDT and am increasing my dose still.

It looks like I'm going to need a high dose with my freeT3 slightly over range. I'm very interested to hear that others are in a similar boat.

Sorry to hijack this blog TarajR, although this maybe relevant to you also. Like you SilverAvocado I have no thyroid (thyroid cancer/RAI x 2) and have struggled with fatigue. I was taking Naturethroid x 2 grains, but it appears all of a sudden that this is not sufficient as the fatigue returned. Am currently on 2 1/2 grains and waiting for the latest blood test on this. I am considering topping up with a bit of T3, and thinking like you that I might be feel better if T3 is slightly over range. Feel free to p.m. if you would like to compare notes.

I don't know the periods of time but do know I had RAI for graves. I was more unwell afterwards on thyroxine than I had been when I was diagnosed. I am now T3 only. It will be over my dead body before I take thyroxine. Looking back I don't know how I managed it for 3 years. You may also be the same but hadn't realised I think after time we end up in our minds thinking ok so if this is it. It must be right because the docs and endos keek telling us we are well. You may then have had some sort of trigger which has made you feel worse. I know I felt dead on thyroxine. I would feel hot but an icy cold radiated off me. My other half could feel it at least 12 inches distance. Good luck. X😀

I was the same, RAI in 2006 and fine for 15 months and then became very poorly indeed. Much better on T3 and T4 mix which has now been taken away from me.

TaraJR, I'm surprised no one has mentioned this so far, but what you describe is quite common. Many people do well on T4 for a certain amount of time, even decades, and then almost overnight it stops working and they need T3. My guess is that it's part of the aging process.

i dont think its anything 2 do with age

only 1 of 6 hypos in my lot can tolerate levo and i dont think it will be long before she too will need NDT

I am wanting to trial NDT - Please would you private message me re where to source & any advice would be very welcome - I currently take 10mcg Liothyronine & 50mcg Levo under NHS. I continue to suffer joint, tendon & muscle pain & wonder if the fillers are the problem. Many thanks in advance

I was originally graves. Part thyroid removed 1983 .Became hypo 1991 and went on Levo. Felt fine til 2001 then wham and I mean wham suddenly felt so ill. Was going through menopause too and now I truly believe that played a part in my thyroxine now unable to work properly. Am now in process of trying to sort cortisol levels before I make a change

Thanks everyone for these replies - interesting reading!

I know all my levels of Vit D, ferritin, folate and B12 are really good. Cortisol level is high at night, so adrenals aren't the best - under investigation by Endo. ACTH test was fine - in the morning of course!

The more I read on this forum, it seems that forum folk research more than some of the medical professionals!

That is the truth!

So refreshing to read this! I had RAI back in 2011 and been on thyroxine since then. No idea how much thyroid I have left and feel rubbish most of the time. A lot of things I read refer to hashimotos but not hypo after RAI with Graves. Was unaware that Graves would continue to flare up until recently. Now looking into NDT. It's definitely a journey of discovery and a continuing realisation that the NHS neither helps or understands (mostly).

Louiseh75, it's most certainly a long journey! And thank goodness for this forum, and Thyroid UK. I've learnt vastly more from there than any doctor has ever told me. And the ITT campaign as well this year was formed to fight the campaign on this whole dire situation. It won't all get sorted quickly, but hopefully we're all galvanised so well now to fight this together!

Well said! Yeah hopefully things will slowly start to change. The NHS can't keep fobbing us off indefinitely now that we all have a bit more knowledge!

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