Thyroxine Supplementation And The Length Needed For Stabilization Of Effects

[Amazoniac]

- Demystifying Thyroid Supplementation | Dannyroddy.com on Patreon

"Besides taking a slow and methodical approach, something I think that is very important to remember is that the half-life of T4 (thyroxine) is two weeks, and thus the full potential of any given dose isn't 'realized' until the end of the second week."​

- Thyroid: Therapies, Confusion, and Fraud

"T4 acts by being changed to T3, so it tends to accumulate in the body, and on a given dose, usually reaches a steady concentration after about two weeks."​

I've read conflicting information on the bloody half-life of typhoid hormones, there appears to be a consensus on it being 7 days for T and 4, but sometimes more.

- A Review of the Pharmacokinetics of Levothyroxine for the Treatment of Hypothyroidism
- Challenges and Complexities of Thyroid Hormone Replacement​

It takes a few intervals to build up the dose to stabilization if there's no loading phase, however 2-3 half-lives are probably enough to judge.

- Pharmacokinetics: Maintenance and Loading Dose | Deranged Physiology

If you rely on figures that are not much conservative, it wouldn't be surprising if a month was required for this. Low and be hold, I could find gurus claiming that up to 8 weeks are needed to get to a steady state.

@Diocino, what is the truth? How long it takes?

 

[Amazoniac]

- Laboratory evaluation of thyroid function: Dilemmas and pitfalls

"Normally, approximately 80% of the T4 and 95% of the T3 administered orally are absorbed."​

Is this correct?
Is the difference explained by an overdose of T4 at a time? Because if not, instead of getting them in an expected ratio of 4:1, it would be something like 3.5:1. It seems modest, but once you consider the half-life, obtaining 20% less than assumed would not negligible in a matter of weeks.

 

[FitnessMike]

- Demystifying Thyroid Supplementation | Dannyroddy.com on Patreon

"Besides taking a slow and methodical approach, something I think that is very important to remember is that the half-life of T4 (thyroxine) is two weeks, and thus the full potential of any given dose isn't 'realized' until the end of the second week."​

- Thyroid: Therapies, Confusion, and Fraud

"T4 acts by being changed to T3, so it tends to accumulate in the body, and on a given dose, usually reaches a steady concentration after about two weeks."​

I've read conflicting information on the bloody half-life of typhoid hormones, there appears to be a consensus on it being 7 days for T and 4, but sometimes more.

- A Review of the Pharmacokinetics of Levothyroxine for the Treatment of Hypothyroidism​

- Challenges and Complexities of Thyroid Hormone Replacement​

It takes a few intervals to build up the dose to stabilization if there's no loading phase, however 2-3 half-lives are probably enough to judge.

- Pharmacokinetics: Maintenance and Loading Dose | Deranged Physiology

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If you rely on figures that are not much conservative, it wouldn't be surprising if a month was required for this. Low and be hold, I could find gurus claiming that up to 8 weeks are needed to get to a steady state.

@Diocino, what is the truth? How long it takes?

Bump

I'm a little rusty with the half-lifes, and this post makes me question what I knew.

Assuming the half-life of thyroxine is 2 weeks, that means that half of the given dose will stabilize after 2 weeks right? then after another half-life, another half of the previous half of the dose will stabilize, and it takes 4-5 half-lives to stabilize the given dose fully?

 

[Sitaruîm]

In the biochemical context, I think, the half-life being two weeks means that if you have X grams of a substance in your system (serum, an organ, whatever) then you will have X/2 of it in two weeks. And (X/2)/2 = X/4 in four weeks, et cetera.

 

[FitnessMike]

In the biochemical context, I think, the half-life being two weeks means that if you have X grams of a substance in your system (serum, an organ, whatever) then you will have X/2 of it in two weeks. And (X/2)/2 = X/4 in four weeks, et cetera.

this is how i understood, but why do many then assume that 2 weeks is needed for the dose to stabilize in the serum, from the above it looks like we need 4-5 half lives for a thyroxine dose to stabilise close to 100%