Wondering about something

[Obsdian]

I know everyone is different so there won't be a precise answer to this. I know when we have a dose increase it takes a few weeks or more to feel the effects. But, I'm wondering how fast medication affects our levels like tsh and t4. Does that take weeks too?

[DippyDame]

It takes 6/8 weeks for a new dose to settle in the system which is why we are advised to wait that long before testing after a dose increase/ reduction

Sometimes we can feel the effects of an increase before then, but serum levels have still to stabilise.

In other words blood test results won't be accurate if tested too soon after changing the dose

[HealthStarDust]

Sensibly, since it takes some weeks for a change to settle, I would expect then that until that stabilisation occurs there would be peaks and troughs throughout the period which could be reflected in tests. However, in order to know this for sure, we’d require near constant testing.

If only there was a smart watch that should us our levels throughout the day when ever we wanted to know. 😠

[Obsdian in reply to HealthStarDust]

I had a similar thought. My son has diabetes and I thought wouldn't it be nice if there was a, sensor for my health too.

[HealthStarDust in reply to Obsdian]

Interesting question mind.

[helvella Administrator Thyroid UK]

I'll just add that some of us can notice even a modest change within a very short time. Like from minutes to hours or a day or two.

This has long been discussed here - some members literally seem to notice nothing for ages. Others have reported the start of the effect of, say, an additional 25 microgram dose, within 15 minutes.

However, even in those who notice very quickly, stabilisation of blood test results can take quite a while.

[Obsdian in reply to helvella]

I only had a first increase (finally), not long ago. Felt absolutely starving the day after my fyrst pill, but not a thing since.

[tattybogle]

if we assume no output at all from thyroid just to simplify the logic :

then with an increased dose of levo , the T4 should in theory start to rise from day 1, increasing evenly over approx 2/3 weeks , then stabilise at a higher level. ( because the half life of T4 is approx 7 days, so it will take 2/3 wks to be stable).

In response to this , the TSH should then go a bit lower, and for some people (depending on the size of the increase ) this may happen much sooner than 6 wks.. but for others it may take considerably longer than 6 wks.

(eg if the TSH has been very low for a while it may take many months to start to rise following a decrease in dose ,..... we have to assume it's a) very individual and b) is dependant on how big a dose change , and c) depends on the thyroid levels in the body before the change , but as there is very little research done on individual patients to see how long it takes their TSH to move and stabilise after a dose change, so we are just guessing, you'd have to test every few days to for a couple of months , to see what is really happening in an individual)

but in reality , if you check TSH / fT4 / fT3 levels any earlier than 6 wks , these levels are very likely to be still changing .

eg. many of us still have some amount of thyroid output of T4 and T3 (assuming our TSH isn't totally supressed)...... and this will be altered by the TSH level.... which is changing ....the changes in TSH level will then effect the amount of T4 / T3 production from the thyroid .... which in turn affect TSH level again .

and, even in someone with no thyroid at all, the deiodinases (which convert T4 to T3/or rT3, and get rid of T3 by converting it to T2) are affected by changes in levels of T4 and T3. So different levels of T4/T3 affect our rate of conversion and clearance.

So it's not just a case of waiting 2/3 wks to see the increased level of T4 , it's also a matter of waiting to see what effect the new levels will have on everything else , and waiting for long enough for all these changes to stabilise.

For another example, if a new dose means we feel better, this will impact our activity levels which will have it's own effect on how fast the body is using the thyroid hormones.

So taking all that into account , waiting at least 6 wks is necessary before we can have a realistic look at the effects of a dose change on bloods .

[Obsdian in reply to tattybogle]

I like the last point you made about if we feel better we may be more active and need more hormone. Never thought of that.

Also, I find it confusing that people keep saying levo replaces t4 it doesn't top it up. Because then some people seem to have hyper times and surely that is because their thyroid did something.

[tattybogle in reply to Obsdian]

because the body's regulating system is so complex , hardly anything in 'thyroid land' is black and white.

it's like saying "yellow and blue mixed together, always gives green"... true , but if you try this with 12 kids , you'll get 12 completely different shades of green and one kid will still manage to come up with brown.

i'm usually the kid who comes up with brown...lol

eg, i've had T4 go way over range on same dose (with no hyper symptoms), lowered the levo dose, and fT4 went UP.

we then increased the dose again , despite the sky high T4 levels , (due to clear hypo symptoms developing on lower dose) and the T4 level went DOWN.

i assume, this was as result of my own thyroid dumping a bit more in there for a few months, due to autoimmune damage occurring, but could also have been caused any number of other things.

or, when i was first treated, my TSH started at 7 ish ,then went to 2.5ish after 7 wks on 50 mcg, then stayed at 2.5ish after 5 mths on 100mcg , and was still 2.5ish after 3 mths on 150mcg levo..... but next time i tested a year later (after about 4 wks trying 175mcg)... we found TSH was then <0.001 .. so my TSH seemed to get 'stuck' at 2.5ish for many months until it got a big enough kick up the bum. (meanwhile fT4 was behaving as expected , going up a bit with each dose increase)

i'd really love to be able to quickly check what my levels are doing on a daily/ weekly basis without sending blood to a lab , but the science to make a gizmo to do this is not going to be possible anytime soon , and may never be , because its a much more complex process to separate and accurately measure the miniscule amounts of free thyroid hormone than it is measure blood sugar, which is relatively simple.