This may have been answered elsewhere but why do some of us need to reduce T4 when adding T3 otherwise we get an increase in hypothyroidism symptoms ?
One would think you'd actually become hyperthyroid with the extra thyroid hormone, so something must be at work to reduce the overall FT3 but what's the mechanism ?
The body converts excess T4 to an inactive form of T3, called reverse T3 or rT3 for short.
There is no consensus as to the role of rT3. Some doctors (mostly alternative doctors) claim it will act as a brake, blocking the action of free T3 (the gas). Others clam rT3 has no biological activity at all and thus will not block the action of free T3. But those who belong to the first category claim that high levels of T4 will increase rT3 levels, which in turn block the action of free T3 (the most potent thyroid hormone), resulting in hypothyroidism despite in-range lab results. Those doctors often recommend adding T3 to NDT to avoid having too much T4 (NDT is 80% T4).
The information is conflicting and it's not easy to know whom or what to believe.
rT3 does not block the action of T3 - that has been disproved (fairly recently and there are sill a lot of out-of-date articles around): they have completely different receptors. I'm sure diogenes can tell you the name of the study. Your body produces both T3 and rT3 all the time (mostly rT3) , but the levels of each are constantly adjusted to rev up (more T3) or slow down (more rT3) your metabolism. So if you have too much (as far as your body is concerned) t4 or t3, you will produce relatively less T3 and more rT3 from T4 (your own or NDT or levo - makes no difference). That also happens if you are dieting or ill. rT3 doesn't, as far as we know, produce any symptoms (but a reduction in T3 would). Some people need higher levels of free T4 than others, even when taking T3. And, of course, if you have hashis your results will vary anyway.
The article in question is:
Endocrinology. 1982 Jun;110(6):2052-8.
Specific nuclear binding sites of triiodothyronine and reverse triiodothyronine in rat and pork liver: similarities and discrepancies.
Wiersinga WM, Chopra IJ, Solomon DH.
Very interesting...I know the information is conflicting, and different doctors contradict each other...which is not making things easier on the patients...
But there seems to be some recent compelling evidence rT3 is not the villain it was once thought to be..."
Looking at previous post with results
healthunlocked.com/thyroidu...
Your FT4 is now very low. Many of us find we actually need good levels of FT4 and FT3
Like you my endo, reduced my Levothyroxine from 125mcg to 100mcg, when 20mcg T3 was added. After 3-4 months, being able to be far more active, my FT4 was dropping and only just above bottom of range. I found increasing Levothyroxine back up, was the answer. Initially put back to 112mcg and retested. It stopped dropping but wasn't going back up. So increased back to 125mcg. Been on that ever since
Your FT4 may be too low and need increase in Levothyroxine
Thanks for replying Slowdragon but that hasn't been my experience I'm afraid - when raising T3 I've always had to lower my levo at some point otherwise hypo symptoms crop up .
I've also noticed the more T3 I add the more 'normal' I tend to feel , so I might be progressing to T3 only or at least predominantly T3 medicated.
Have you had DIO2 gene test?
thyroiduk.org.uk/tuk/testin...
I haven't no. I already know I don't convert well so didn't see the point in RT3 and additional tests.
It's genetic test and has proved very helpful for many of to prove needing addition of small dose of T3 and get this on NHS prescription as result
"To explain this paper briefly, the DIO2 gene activates tri-iodothyronine (T3) and the researchers found that a tiny fault in this gene could mean that although the body gets enough T3, the brain doesn’t.
The researchers found that patients on levothyroxine (T4) alone felt worse if the faulty DIO2 gene was inherited through one parent and worse still if they inherited the faulty gene from both parents."
Thanks SlowDragon. Luckily I already have an NHS T3 prescription.
Also as you have Hashimoto's, levels vary a lot
Important to regularly retest vitamin D, folate, ferritin and B12
These need to be optimal
Are you on strictly gluten free diet or tried it?
🤷♀️ I’ve never heard of that and in my case I think my Levo was reduced too much, I do feel brilliant atm but still in the back of my mind I’m cautious about my FT4 dropping anymore. I think for longevity it could have stayed at a higher dose. Everything is done so cautiously and I understand why but if one doesn’t have a high FT4 in the first place then I don’t think Levo necessarily needs to be reduced when introducing T3.
This is interesting.
I’m doing bloods tomorrow so will see what those show but I found in the past when Prof Toft increased my levo past anything I had done before, I initially felt better then it tailed off. After another increase the symptoms remained the same. So I’d agree with the “higher dose -hypo symptoms” theory.
Since adding T3 I’ve definition improved. But I seem to have periods of about 3 weeks following each T3 increase where I’m symptom free (my main one is muscle weakness). Then it returns. So far, I’ve decreased levo initially to 125mcg and introduced 5mcg T3, increasing everytime symptoms returned until now I’m at 25mcg T3 and still 125 levo.
So my issue (in the absence of bloods) is now this: increase or decrease?
I don’t feel any overmedicated symptoms at all. None. But I do have crazy muscle weakness and a touch of lethargy at the moment.
Bloods will help but what to do next!
it's after 1 am and I'm having a biscuit with my beta blocker lol That is totally my experience too. I think everyone is different and in some people upping Levo would counteract the effects of t3 (happening to me now). I thought I should have upped my Levo to get more stable as my levels dropped, but that was not the case. I have now become more hypo with palpitations, like there is some mechanism or something. Looking at my results from when I felt good, my ft4 was never high in range. If I convert poorly why adding Levo should help me? All it does it reduces my tsh and conversion, but doesn't give me enough t3. I was glad to find your post, I was wondering about the same thing the last week and finally have made a decision to lower my Levo.
When my Endo left my Synthroid dose as it was and added 10 mcg of lithothyronine to the mix I was good for about 5/6 months. Then started having all kinds of hypo symptoms. After about 3 months of that crap I had tests done. My FT4 was over range, My FT3 was at the bottom of the range and my RT3 was over range by 3 times. It's no wonder I had hypo symptoms!
Adding T3 to T4, not sure which way to go
Argument for *not* reducing T4 when adding T3
Raising t3 without raising t4
Do I need to tweak my T3 or T4? After feeling so much better hypo symptoms have returned. 
Have been adding t3 to t4, symptoms improving but ft3 hardly moves
