What is the half life of T3?

[Totoro]

I think I did know, I've forgotten!

I did a bit of a google and I'm coming up with conflicting answers of 8 hours to 1 - 2 days.

[Lily905]

The Hospital sayes it takes 10 days to go from your body. Which is why its used for the first year after Thyroid Cancer. So you can be taken off it for treatments.

[helvella Administrator]

Totoro,

What you are finding is quite common. In someone who is severely hypo, whatever they take will get used up quickly. In someone who is less hypo (or even hyper), then it will hang around a lot longer. So half-life is a bit of a variable.

I suggest somewhere around a day in someone who is not too far off properly treated. Or a student in a trial!

Liothyronine.

After oral administration of L-triiodothyronine sodium (which is more readily absorbed than T4) peak levels of serum T3 are observed within 2 to 4 hours (21).The serum T3 concentration may reach elevated values after a single dose of 50 µg or even 25 µg, sometimes associated with cardiac symptoms like palpitations (22) . The half-life of T3 is approximately one day. Preparations of L-T3 are useful in the management of patients with thyroid cancer to shorten the period of hypothyroidism required for diagnosis and treatment of remaining tumor tissue with 131I.

thyroidmanager.org/chapter/...

Rod

[Totoro in reply to helvella]

Thanks, I'm trying to work out if I take e.g. 75mcg in 3 x 25mcg doses at 7am, 12noon and 5pm when would the concentration of T3 be highest in my blood. Because maybe the way I'm taking it is giving me a high concentration in the evening when I want to go sleep.

I actually take 85mcg at the moment and have just been trying taking it at different times of the day or even all in the morning. I get the impression it's a very individual thing, what works best for one person won't necessarily work best for another. So I'm trying out different things.

I just tried taking it all in the morning but that leaves me knackered in the afternoon. I've tried a version of the CMT3 which I'll look into more and now I'm going to try taking more T3 in my morning dose.

So instead of 35mcg, 25mcg, 25mcg I'll try 45mcg, 25mcg, 15mcg. Or even more in the morning. It feels like an art form as much as science!

Totoro x

[helvella Administrator in reply to Totoro]

I understand what you are saying.

My guess is that the serum peak would occur around two hours after the third dose - which is 7pm.

My logic is that each dose will result in its own peak towards two hours after ingestion. But they do not fade away quite so quickly. So the second dose will add to the fading tail of the first dose. The third dose will be on top of the even more faded tail of the first dose plus the tail of the second dose.

What could be wrong-footing you is that while the direct metabolic effects of T3 are relatively fast - within hours and up to two days - the effects on gene expression seem to pick up two days after the dose and ripple on for days after.

Also, some people seem to sleep better if their thyroid hormone levels are not too low at night...

(I do not take T3 so this is based on my understanding of things.)

Rod

[Totoro in reply to helvella]

That's really interesting. What do you mean by "gene expression"?

I have recently wondered whether T3 was having a different effect (time wise) on my heart and my brain.

Totoro x

[helvella Administrator in reply to Totoro]

Trouble is, most of the material about gene expression is very much research and tends to the unreadable!

For example:

jpet.aspetjournals.org/cont...

Got quite a number of hits by searching for "t3 gene expression" - maybe you would find a more readable paper?

Rod

[marram in reply to Totoro]

The conclusion that you have come to is almost exactly the same as the conclusion reached by Paul Robinson in his book 'Recovering with T3'. He also mentions that some people find it better to break down the doses ever further, up to 5 times a day, but however many doses, it tends to suit most people to take a reducing dose as the day goes on so the T3 residual effect does not result in too high T3 at the end of the day.

[Totoro in reply to marram]

Hi Marram,

I've just ordered the book and look forward to reading it. I did worry I would get information overload from it and the CMT3 method would involved lots of tests and supplements that I couldn't afford right now but there will probably be useful info in it that I could do with knowing.

I'd had the impression of T3 only dose splitting before that you take a bit more in the morning. An endo also suggested, when he was advising me to take 75mcg, that I should take 30mcg, 25mcg then 20mcg and this is similar to what I was doing on 85mcg.

However I'm now seeing that the first dose probably needs to be a much bigger one. Today I'm trying 50mcg, 25mcg, 10mcg.

Totoro x

[Heloise in reply to Totoro]

stopthethyroidmadness.com/t...

[cthaffy1956 in reply to Totoro]

Hi Totoro, I have just received an email from my IGP. He tells me that T3 should be taken 3 times a day, with the highest dose being in the morning.

I will be taking 20mcg at breakfast, 10mcg mid afternoon, and 10mcg at bedtime to see if that helps.

cheers

Chris

[helvella Administrator in reply to cthaffy1956]

cthaffy1956,

You might not have noticed that this thread is over four years old.

[nobodysdriving]

I know that if I don't take my T3 as I get past the 48 hours of not having any I start to deteriorate, by 56 hours I feel bad.

I take 160mcg daily all at once when I wake

[Totoro in reply to nobodysdriving]

I've tried taking my 85mcg in the morning when I wake but about 6 hours later I was crashing badly and had to have a strong coffee and some chocolate cake to get me going (I was at a fair with friends and had to have this just so I could walk home without a struggle). Coffee and chocolate cake as medicine are ok with me though

This is the second day I've tried taking it all at once in the morning. I'm pleasantly surprised that I didn't have any feelings of hyperness in the day but did crash later. I wonder what would happen if I took more in the morning?

Have you always taken your T3 at once in the morning or did you ever take it spaced through the day? If so, did you take more T3 when you changed to one single morning dose?

Totoro x

[nobodysdriving in reply to Totoro]

Hi Totoro, I can take my T3 at once or staggered through the day it does not make a difference, however when I was at a lower dose (<100mcg) I used to crash too if I did not multi dose.

I tried only recently to take my 160mcg multi dosing 4 times a day, a nightmare, much much better once a day for me, and no I do not need to take more if I take it at once now.

[Totoro in reply to nobodysdriving]

Hi,

May I ask what your remaining symptoms were when you were on 100mcg and multi dosing?

I wonder what I would feel like if I took more T3 but just once a day. Sometimes I feel like my brain needs more T3 but if I take more than 85 -90mcg my heart starts to beat too strongly when lying down at night (not very strong, but noticeable).

But if I was on a bigger dose but only in the morning I probably wouldn't get that as enough T3 would have gone from my body by nighttime.

Why don't people like yourself and others that take 100mcg + all at once in the morning feel hyper in the morning/noon?

I had a slight concern I would feel this when I took 85mcg all in the morning but it didn't happen at all, neither mind nor body. But if my blood had been tested then it surely would have been quite over the top of the range.

Totoro xx

[sweet_b in reply to Totoro]

Hi Totoro... did you get the dosing sorted out?

[Totoro in reply to sweet_b]

Hi,

Yes, I ended up on 90mcg T3only (I was gradually reducing my T4 and increasing my T3 over many months) and I take it 45mcg at 7.30am, 30mcg at 12.00 and 15mcg at 4.15pm.

I've been dieting to lose weight and have been able to reduce my T3 a little from this but am waiting to chat to my endo about this. I've found I'm pretty sensitive to dose changes, up or down. I wish T4 had worked for me because it's a lot easier to take.

Tototo x

[sweet_b in reply to Totoro]

Thanks for responding. Tricky to figure out!

[Stourie in reply to Totoro]

I take 80 mcg of t3 at bedtime and sleep all night most nights. It usually only takes about 10 mins to fall asleep.

Jo xx

[Totoro in reply to Stourie]

Hi Joanna,

I've tried taking a small amount of T3 (5mcg) at bedtime but it seemed to wake me up. I've found before that if I take T3 after around 7pm it does keep me alert more when I'm trying to get to bed.

My case is complicated by the fact that I have sleep problems (awaiting sleep clinic results but they said it would take 2 -3 months for those results!!) I do feel sleepy, tired (sometimes exhausted), yawning at 10pm - 11pm but I go to bed and stay awake (sometimes getting up, sometimes not) until at least 2am.

Perhaps if I can resolve the sleep problem I can I could take T3 at night. I had hoped that T3 might help my sleep problem but haven't found a way to help that yet.

Totoro x

[Stourie in reply to Totoro]

When I was on t4 I didn't really sleep great. When I moved to t3 I tried splitting it first for a few months and didn't sleep to well then I read on here about taking it all at bedtime and it worked. Maybe the small dose has the opposite effect. Sorry don't really know.

Jo xx

[Vickiti]

An associated question if I may ...

How long would I have to stop T3 (that I take in addition to T4) in order for it not to show any effects in a blood test?

[nobodysdriving in reply to Vickiti]

if you want NO effect on fT3 stop it at least 48 hours before, however the TSH will remain suppressed for a few more days and possibly will stay suppressed depending on amount of levo you take.

[poing]

I looked this up once...

jci.org/articles/view/106835

The answer here appears to be between 0.6 and 1.4 days.

There's an element of "it depends" with T3 lasting longer in the body in people that are hypO and being consumed much more quickly hyPERs. That sort of makes sense to me, because when you are hypO, your metabolism runs more slowly.