Showing the delay in TSH responses to thyroid hormone changes

[diogenes]

I can't recall if I have sent this in before, but it is a good paper showing that TSH delays its response to thyroid hormone changes, sometimes over a very long time indeed. Should be useful in demonstrating to GP's that suppressed TSH will not easily respond to T4 changes and that they should not expect to see changes in the medium term - ie don't further reduce doses just because the TSH hasn't changed. Paper downloadable.

REVIEW article

Front. Endocrinol., 14 June 2016 | doi.org/10.3389/fendo.2016....

A Review of the Phenomenon of Hysteresis in the Hypothalamus–Pituitary–Thyroid Axis

Melvin Khee-Shing Leow1,2,3,4,5*

[helvella Administrator Thyroid UK]

The abstract is excellent.

[Gingernut44]

Thanks for posting, this could be very useful

[Lalatoot]

Very interesting and understandable. thank you.

[Tythrop]

Ta, ..GPS I thought they were extinct .

[JGBH]

Thanks again for a most helpful article.

[fuchsia-pink]

You are a superstar, DIogenes, thank you

And thank you too to Health Unlocked for allowing us to save posts

[Charlie-Farley]

Now that is useful! Thank you so much. I’ll be able to counter any attempt to muck about with treatment having a reference like this.

[Serendipitious]

Really interesting based on the extract. Thank you.

I just wonder if anybody knows how long it can take to raise TSH? Having been on Metavive for a few years and now having transitioned back to Levothyroxine but 3 months later TSH is still around 0.01-0.05. Far too low.

[tattybogle in reply to Serendipitious]

levo is just as capable of keeping TSH at that low level . it's not just T3 content that will keep it that low.

If your 'effective' dose has not reduced much, then stopping NDT or Metavive and replacing with similar amount of levo might not allow TSH to rise at all , unless you lower your Levo dose quite a bit (probably to the point of 'not enough'.. for a few months )

I might be a weird exception ,so take the following examples with a pinch of salt .... but my TSH doesn't seem to move much unless it get's a big shove.

Subtle adjustments in dose don't seem to move it at all, no matter how long i wait.

Unless i tip my dose into 'really too much' or 'really too little for 6 months ' or 'non at all for a week' .. then all of a sudden it shifts , and faster than you'd think it's supposed to .

e.g. After 10 days with no levo, TSH went from 0.05 to 7.8 on day 11.. (it had been at 0.05 for over a decade on 150mcg levo)

e.g When i first started Levo, 7 weeks @ 50mcg gave TSH 2.9 / 5 months @ 100mcg gave 2.5 / 3 months @ 150mcg gave 2.7 ...... a few months later i tried increased dose of 175 ish for about 3 weeks and then tested .. i found TSH was 0.001

But when i lowered Levo back to 150mcg . TSH didn't return to previous 2.7...it only came back up to 0.04 /5 ish and stayed there. .....didn't make any difference if my fT4 was 60% or 120%... TSH stayed at 0.05 for 15 yrs (apart from it's brief adventure up to 7.8)

e.g. In 2020 my levo was reduced over 8 months from 125 to 112.5 then a step too far to 100 ..... which only had minor effects on TSH .. 0.04 / 0.09 /0.5

But i was so clearly undermedicated on 100mcg (digestive system ground to a halt ), that even the GP agreed to put it back up to 112.5mcg...... we both expected TSH to lower again to 0.05 ish ... but lo and behold it went up to 1.9..... about 6 months after you would have expected it to , and despite the fact that i'd been back on higher dose of 112.5 for the last 6 months.

[June25 in reply to tattybogle]

Great post tattybogle, and really informative for those of us who who have never understood the vagaries of how our TSH moves, or in my case doesn't move.

[tattybogle in reply to June25]

i think of my mine like a 'stuck' shed door in winter ,where you have to push increasingly hard on it to get it to open.

nothing, nothing, nothing .... too fast .

[June25 in reply to tattybogle]

Wonderful imagery tatty. Works for me.

[wellness1 in reply to tattybogle]

Thanks so much for describing your experience. I'm giving a bit of attention to this and it is anything but straightforward (despite what many clinicians say).

[tattybogle in reply to wellness1]

Getting hold of 20 yrs of historic test results that included fT4 , made it easier to understand what might be happening... after the event.

If i had been trying to figure it out as i went along .. i'd be utterly confused by the test results i was seeing in response to dose changes

( as presumably my GP's were at the time... no wonder they always looked at me with that quizzical look that means "are you muddled ?, neurotic ?, or just lying ? " )

.... mind you, i'm still confused anyway , cos my fT4 goes all over the place for no apparent reason .... including up when i reduced dose, & down when i increased dose.. go figure .

[Serendipitious in reply to tattybogle]

Thanks this is really useful. I will also create my own post and see if I can get other peoples experiences.

I don’t know how I can survive on 75mcg of T4 again in a bid to get TSH into the normal range let alone on no medication, I cannot even contemplate that. Ugh!

[tattybogle in reply to Serendipitious]

No . well for the avoidance of doubt ... i absolutely wasn't recommending you try either approach . Your body won't appreciate you doing either of them , and it may take months to forgive you if you do .

I should have added a Blue Peter Warning " don't try this at home"

Find the dose you feel best on ... if TSH happens to end up below range on that dose ...so be it .