I'm hypothyroid and I'd like to step down my T4 dose from my current 200 mcg down to 150 mcg. I know I can simply start taking 150 tomorrow and wait 6-8 weeks. However, I'd like to adjust some other things too, so would like to reduce the wait period.
One thought I had was, I could go down to 0 T4 for several days. This would very quickly deplete FT4 (half life of ~1 week). After several days I could start on 150. To my mind this would be vastly faster than the normal approach. However, how many days should I go with 0 doze? Perhaps it shouldn't be 0, but some other lower dose like 50 or 100? Lastly, this in theory could produce some wild hormone shock/fluctuations, which would mean doing this might be quite detrimental e.g. although my blood level could be where i want faster, but how I feel might be out of kilter for much longer, maybe months?
To reiterate, I would definitely prefer to switch down as fast as I can. Normal 6-8 week wait time would be the last resort.
Has anyone done this kind of step down. Any suggestions?
Written by
ak_83
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The 6 to 8 weeks "rule" is how long it typically takes for blood test results to stabilise after a dose change.
That will apply if you change to 150 tomorrow, went through days of nothing, or anything else.
The vast majority of the change of circulating T4, in particular, occurs very much faster than that. If you could afford to have your blood tested every day then you would very likely see most of the change within days.
However, in your post 11 days ago, you said you were on 150 micrograms of T4. Which is perplexing.
Your point about half-life might make some sense but...
The halves for a dose reduction should be of the difference in dose.
The body can, and does, to some extent eliminate excess levothyroxine. If 200 is genuinely too high a dose, I would expect that it would fall somewhat faster than a simple arithemetic approach suggests because of this.
On the other hand, if 150 is too little, I'd expect the fall to initally be somewhat faster because it is being used up and not completely replaced!
I so wish we had a way of testing similar to a blood pressure device or oxygen saturation thingy. Even though we don't have such devices, I wish more research projects did very frequent testing instead of leaving the subjects weeks or months and just taking a snapshot at the beginning and end of the trial period. (Usually without regard to time of day, etc.)
Yes I should have pointed out it's the difference. Of course if you stop alltogether for a few days the difference is the full dose!
Also, the half-life is affected by how high a dose you are on, shorter the higher the hormone levels.
I don't think 'too little' means the hormone is being used up. I've never seen any measure but I suspect very, very little hormone is 'used' in the sense it has binded to receptors. Only a tiny fraction of the available hormone is free. In addition thyroid hormone receptors have to be staturated in T3 for several hours before a T3 molecule binds to the receptor. So, it is likely that the 'used up' concept is erroneous. This is supported by the observation that the half life of thyroid hormone increases as the levels fall.
Quantum physics has advanced so rapidly in recent years (alas my ability to understand it hasn't). I long for a day when we are able to image the concentration of T3 in the body and zoom right down into the cellular level.
I think, in terms of T4, you can view the process as "used up" - with the classic one third converted to T3, one third to rT3 and one third eliminated (e.g. sulphation pathway). But the precise points of those so-called thirds can shift.
We have gone from a view of thyroid hormone as a signal to a cell, to sugegsting the view that it is somewhat like a nutrient. A vitamone?
Oh. Patients tend to think of 'used up' in terms of hormone action, how much has bound to receptors. In the sense T4 is converted to other molecules and eliminated then it is indeed used up as measured by the elimination half-life.
This 150 ncg was Synyhroid, which was given to me and them saying that they are all equivalent. I got my blood test result and turns out Eltroxin (my usual) 200 mcg is equivalent to 150 Synyhroid. So my step down never happened... Now I'm going back to Eltroxin 150, which should hopefully be an actual step down this time!
How many days does the blood FT4 would settle down after, a week, two weeks?
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