Useful article on reverse T3

[jimh111]

"Reverse T3 or perverse T3? Still puzzling after 40 years?"

This article is a good introduction to thyroid hormones and reverse T3 ccjm.org/content/85/6/450 . It gives an overview of the history of thyroid hormones and is very readable. It does over-simplify the deiodinases (e.g. D1 also produces rT3) and in its concluding remarks loses track a bit when recommending using TSH to titrate levothyroxine. On the whole it is interesting and delightfully gentle on the brain for such a complex subject.

[TSH110]

Interesting article, thanks for posting.

I notice they trot out that nonsense about T4:T3 ratios:

thyroidpatients.ca/2019/05/...

They also appear to be against combination therapy so I do wonder how much they really understand. Do they get that the thyroid TSH etc is all aimed at keeping free T3 within narrow parameters for health? If they are anti combination therapy I can’t see how they can. Interesting that they make no mention of the original treatment with NDT as if only synthetics ever existed for therapy.

My simpleton view of reverse T3 is it’s a safety valve to quickly dissipate any excess T3 so the narrow free T3 parameters are maintained. But I could be completely wrong of course.

I am suspicious that non thyroidal illness is being used as yet another excuse not to treat people who really are hypothyroid.

[jimh111 in reply to TSH110]

I don’t like T3:T4 ratios because they are dynamic not static - for each individual. If our fT4 falls TSH rises and this stimulates more T4 to T3 conversion (as well as more thyroidal secretion). So, we have no ideal T3:T4 ratio but I’m happy to accept the in healthy people about 20% of T3 comes from the thyroid.

I think the Canadian Patients article is unnecessarily complex … because it over simplifies! What I mean is that it falls into the trap of discussing ideal T3:T4 ratios for medication. This is misleading because T3 and T4 have different absorption and different elimination half lives. So, the ratio you put in your go is not the ratio that ends up in the blood. Rather than trying to work out what dose to take just take divided T3 doses and measure TSH, fT3 and fT4. You can then restore normal hormone levels - but it probably won’t work.

The additional complication is that if you need T3 it is probably because you have impaired conversion and the most likely cause is insufficient TSH secretion due to a down-regulated axis or chronic illness. TSH stimulates deiodinase which regulates intracellular T3, as well as supplying circulating T3. If you have this problem restoring serum T3 will not be enough to compensate for the loss of T3 that comes from local T4 to T3 conversion. You will need higher serum fT3 than normal. It’s a complex topic which I describe here ibshypo.com/index.php/subno... .

Non-thyroidal illness is valid but endocrinologists fail to separate out acute and chronic cases. If someone has a heart attack or severe burns it is perfectly valid to say thyroid hormone levels are affected for a short period and we should not attempt to ‘correct’ them. (Assuming we don’t know for sure that hormone therapy would be helpful). However, chronic conditions such as very painful arthritis can have the same effect and it seems perfectly reasonable to intervene in these cases to restore clinical euthyroidism.

[TSH110 in reply to jimh111]

Thanks for your reply amd the link which I’m looking forward to reading. I agree the ratios are constantly being adjusted with. a functioning thyroid to suit the situation.

I was very poorly indeed before I got diagnosed with atropic autoimmune thyroiditis and despite having a very good endo my freeT3 never returned to anything near normal on Levothyroxine if I took more I felt terrible if I took less I felt terrible and if I took the same I felt terrible. After two years of a very grim, flat, stupifying realty on T4 monotherapy I decided I had nothing to loose by trying NDT - I’d seriously consider topping myself. It had immediate and highly beneficial effects - depression annihilated 😁 brain fog cleared, energy levels restored, four stone of fat I put on vanquished without a mummur and I returned to my normal size, etc. I remain very well on it.I have one gene for DIO2 polymorphism for poor conversion and one fue thyroid hormone resistance so maybe these are relevant to my inability to convert T4 to T3 efficiently. I find it odd that my close relatives on Levothyroxine feel absolutely dandy on it. I knew something was really up when my progress on it was so glacial they felt hugely better within weeks of starting it. I’d love to know the reason for our different response to T4. One tried NDT out of curiosity just to see and felt possibly a bit better but not enough to swap to it. Nothing like what I experienced which was akin to visionary and miraculous.

Interesting what you say about NTI. I presume the body has good reason to reduce the levels as part of a healing process. I must read more about it.

[jimh111 in reply to TSH110]

I think the most common and most potent cause of impaired T4 to T3 conversion is a subnormal TSH, the pituitary producing less TSH which has reduced bioactivity. TSH regulates conversion, so if it is lower than expected (for fT3, fT4) there will be reduced conversion. In this case taking levothyroxine will lower TSH and hence reduce conversion further, a vicious circle.

[TSH110]

Thanks for all the helpful info