How should Levo dosing work - a 101 explanation needed please

[N5girl]

sorry my brain is mush. I have read a lot of posts, tried Dr Google etc. I could do with a really basic explanation to help understand what my Endo is likely to talk about this week re: Levo dosing.

what I think I know… Levo replaces what’s missing, T4. This results in lower TSH and higher T3 (assuming you can convert T4 to T3).

What should drive the doctor to increase the dose? Will it be a combination of T4/T3 AND TSH or is it just T4/T3?

For example, does the Levo always reduce your TSH level, but its impact on T4/T3 depends on the amount taken (and how well you absorb it, convert it).

In very simplistic terms, if you took Levo for a few months, would your TSH drop to a ‘normal’ level but your T4/T3 may not increase much because your are on an insufficient dose? Or will the reduction in TSH also depend on how much Levo you are taking?

Background: Diagnosed with Hashi. Started on Levo at 25mcg 10 days ago. Felt even worse with excessive fatigue (without any other change). Consultant has increased dose today to 50 mcg because TSH has fallen (no numbers until end of week). I am planning to try going GF once I get accustomed to the Levo. Will also do a thorough Vit review beyond insufficient Vit D

[tattybogle]

You do need to wait on same dose for at least 6 weeks before you can see what effect it has has on TSh / fT4 / FT3.

TSh needs this amount of time to stabilise, there's no point looking at it earlier . and until TSH has stabilised T4 /T3 levels can continue to change a bit .

and it's not a case of ' if you so this ..that will happen' .... it's very individual.

some people will have TSH / fT4 move quite predictably when starting levo and increasing doses , and some won't be predictable at all .....for example , my TSH lowered quite predictably from 7ish to 2.5 ish after 7 wks on 50mcg , and then illogically stayed at 2.5 ish after a few mths on 100mcg and was still at 2.5ish after several more months on 150mcg .. then a year later , it had fallen to 0.05ish on same dose

But basically ... when you add Levo, your fT4 should initially go up a bit ... and your TSH should initially fall a bit , and if that dose is insufficient then over time you may see the TSH start to rise again.

GP's will increase dose if TSH is still over range.

Better informed GP's will try to get TSH below 2. and will be willing to increase dose if it's over that and symptoms remain a problem .

They will also look at fT4 (if it's been tested) .... they won't usually be willing to increase dose if fT4 is near the top of the range.

fT3 is a bit complicated .. before taking any levo , the high TSH 'boosts' the amount of T3 your thyroid produces ... this 'boost' is turned down when TSH level lowers .... so once on levo , it's common for T3 level to fall...... and it's then a case of needing to be on enough levo before you can asses conversion ... ie. when on a dose of levo that gives TSH 1 ish with a decent fT4 level around 75%...THEN you can can have a look at fT3 level to see how good conversion is.

[tattybogle in reply to tattybogle]

These two posts may help a bit : healthunlocked.com/thyroidu... explanation-of-what-*high-tsh-is-telling-us-when-our-ft4-level-is-normal-on-levothyroxine-the-shoe-size-analogy.-

healthunlocked.com/thyroidu.... -list-of-references-recommending-gps-keep-tsh-lower-in-range-

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A Helpful Quote from another members GP ,on what to expect when starting treatment for hypothyroidism.

"The way my new GP described it was ..."You know how your body is continually breaking down and rebuilding itself? Well, the thyroid controls the rebuilding, so if it isn't working you carry on breaking down but don't rebuild properly. Your body now has a lot of catching up to do, which will take a minimum of 12 months, probably a lot longer...." or words to that effect. He also said it would be a saw tooth recovery (get better, go backwards a bit, get better, go backwards a bit) and he's been right so far."

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[N5girl in reply to tattybogle]

Thanks. I was fully expecting to wait 6 weeks for a retest but my consultant tested TSH / F4 when testing my new vit D level (I had been on a mega dose programme). This ‘revised’ TSH level was used to increase my dose. I am not going to object to the increase because I feel atrocious and everyone keeps telling me 25mcg is too low to start given my age.

I was not expecting the test and I had a Coke before it because I was feeling so awful and needed to drive. So I suspect that the test score may not be that reliable in terms of measuring TSH at its highest point.

I don’t think the actual TSH score mattered to the Endo , it was more the fact that it had moved down which suggested that the Levo was moving things in the right direction. which is what you said happens to quite a few people.

I also was prepared for it to take months / years because it runs in the family. I also expected it to involve more than just popping a pill because it is autoimmune (for some people). What I wasn’t expecting was to feel so much more tired in the first week. It’s a type of fatigue that I have never experienced before - probably akin to the type of jet lag you get by going to Australia.

Thanks for the resources.

[tattybogle in reply to N5girl]

agreed re. increasing to 50mcg without waiting 6 wks .... 25mcg is usually too little unless you're medicating a geriatric mouse with a heart compliant

[Forestgarden]

Tsh is made by the pituitary in the brain. More tsh is made when thyroid hormones (t4 and t3) are low. So as you are now taking t4 (levothyroxine), you've increased your thyroid hormones and you would expect the tsh to fall. Its a negative feedback mechanism. The aim is to increase your thyroid hormones by taking levothyroxine, and the docs 'monitor' this by looking at your tsh when you have a blood test. So, tsh is an indirect measure of how well your thyroid hormone replacement is going. The docs should increase your levo (slowly, because there's a lot of lag) until you are feeling better. Unfortunately, most don't actually ask us how we're feeling on a particular dose, they only look at the tsh being 'within range'.