0.6 mcg of T3 per kg of body weight?

In the past few days, I have seen two sources indicate that, as a rule of thumb, a person taking T3 should take 0.6 mcg per kg of body weight. This would mean that 3.5 grains of NDT, which seems to be a common replacement dose, contains the amount of T3 that a person weighing 50 kilograms would need. Sounds strange to me, or does this rule of thumb only apply to people on T3 only (as a rule of thumb, the replacement dose of T4 is often said to be 1.5-1.6 mcg per kg of body weight)?

[greygoose]

Rules of thumb aren't much use to a hypo. It's the rule of taking hormones you need to follow: start low and increase slowly; and keep increasing until you feel well.

The problem with rules of thumb is that doctors tend to take them as set in stone and invariable, because it makes life easier for them. And a rule that doesn't specify if it's meant to be for NDT, T4+T3 or T3 only, isn't much of a rule. I'd forget it, if I were you. There are so many variables.

[Aurealis]

greygoose reply made me laugh, in a good way - I sometimes wondered if there was a quick route to the right dose, but no I don’t think so. Even if the formula is right you still don’t know how much you have to take to absorb that amount, or how much extra you might need to take to make sure the right amount gets to the individual cells. x

[greygoose in reply to Aurealis]

Exactly.

[helvella Administrator Thyroid UK]

Are these sources publicly available? It might be interesting to follow them up.

[Hidden in reply to helvella]

Helvella, there's a recent review paper that looks at dosing T3 in the research trials. It basically says that a range of dosing formulas are used none really based on evidence and varying between a ratio of T4 to T3 of anywhere between 14:1 and 20:1. I.e. no one can really say but a bit of maths looks like you have a plan.

Dayan and Panicker Thyroid Research (2018) 11:1 DOI 10.1186/s13044-018-0045-x

REVIEW Open Access

Management of hypothyroidism with combination thyroxine (T4) and triiodothyronine (T3) hormone replacement in clinical practice: a review of suggested guidance

Colin Dayan1 and Vijay Panicker2*

[helvella Administrator Thyroid UK in reply to Hidden]

Thank you - I think your summary makes a lot of sense.

Direct link:

thyroidresearchjournal.biom...

Will read later.

[Hidden in reply to helvella]

This is where I found the 0.6 mcg of T3 per body weight (but I now see that it was given IV during a trial period; not sure if it makes a difference).

The other figure I found on the site tiredthyroid.com.

But I guess Greygoose is right that those figures are statistical more than anything and do not reflect reality for most patients.

[helvella Administrator Thyroid UK in reply to Hidden]

Tired Thyroid often makes a lot of sense.

But you are right, intravenous is different. Speed of delivery and no interference from anything in the gut nor imperfect absorption.

If these figures were given with a proper degree of warning and expkanation, they do have a usefulness. For example, "a patient with no thyroid function will be unlikely to need less that n.n microrgams per kilogram but might need more due to absorption and other issues".

After all, a doctor needs to have some idea where to start!

[Angel_of_the_North]

I've never heard that - where is the journal article to support it? I have heard the 1.6mcg of T4 per kg as a starting point for patients after thyroidectomy. Since, AFAIK, no official medical body supports T3 only or even T4/T3, I suspect that this info is "made up" (I was going to use a B word)