Why do we switch to iu, and what a z-score actually measures?

Bastogne22

Explorer
Joined
Mar 18, 2026
Messages
33
Reaction score
0
Location
IL
Would somebody break this down as if I were in the 5th grade?

Where does the habit of talking in iu come from? The strength of the vial still has to matter, doesn't it? And why not keep describing things as 1mg/2mg/3mg/4mg? Is it true that once you're in your late 40's/50's, IGF-1 matters less and a z-score is nothing more than how you stack up against other people your age?

TRT and Reta are what I'm running now. Tesa is something I want to add, but I'd rather read up and understand it properly before I start pinning anything.
 
woundcarping said:

HGH is the only one measured in IU; nothing else here is.
Somewhere — not this forum, I don't think — I'd come across people describing secretagogues such as Tesa in iu too.
 
Bastogne22 said:

woundcarping said:

HGH is the only one measured in IU; nothing else here is.
Somewhere — not this forum, I don't think — I'd come across people describing secretagogues such as Tesa in iu too.

What they may be describing is "units" on the insulin syringe they draw with — insulin units — rather than IU for the secretagogues themselves. Those are dosed by weight.
 
The one compound dosed in IU, as far as I know, is HGH. Why that is I couldn't tell you, but for hgh the conversion works out to 1iu = 0.33mg. That figure only holds for HGH, mind you — each compound measured in IU carries its own conversion rate. Convoluted is the polite word for it IMO.

With Tesa, the other peptides, and ASS, mg is the unit across the board. You'll hear people quote their dosage in “units”, but that's someone who doesn't know what they're doing, quoting injection volume (0.01ml = 1unit) instead of the actual dosage.
 
CNCCurrency said:

woundcarping said:

HGH is the only one measured in IU; nothing else here is.
iu's are what HCG comes in too, as far as I know.

Fair enough, that hadn't crossed my mind — and they certainly belong in this “space.”

HCG counts as a protein rather than a peptide (237 amino acids, while peptides run 50 or less.)
 
woundcarping said:

CNCCurrency said:

woundcarping said:

HGH is the only one measured in IU; nothing else here is.
iu's are what HCG comes in too, as far as I know.

Fair enough, that hadn't crossed my mind — and they certainly belong in this “space.”

HCG counts as a protein rather than a peptide (237 amino acids, while peptides run 50 or less.)
hgh is the same story, and who here brought up peptides? My impression was that mg and iu were the whole subject.
 
Oxytocin sold for pharmaceutical or veterinary use is measured in IUs too; the grey space version gets dosed by weight, though.
 
CNCCurrency said:

woundcarping said:

CNCCurrency said:

woundcarping said:

HGH is the only one measured in IU; nothing else here is.
iu's are what HCG comes in too, as far as I know.

Fair enough, that hadn't crossed my mind — and they certainly belong in this “space.”

HCG counts as a protein rather than a peptide (237 amino acids, while peptides run 50 or less.)
hgh is the same story, and who here brought up peptides? My impression was that mg and iu were the whole subject.

Which is likely why my reply opened with “you are correct.”

In my head, “this space” meant peptides — yet HCG does get talked about commonly.

Plenty of vitamins are dosed in iu, a leftover from the old days when potency varied so much.
 
The reason was already in my head, having read it just days ago. Claude supplied this:

IU (International Units) exist because the usual yardstick for hormones is biological potency — how much effect they produce in a standardized assay — rather than mass (mg). HGH, insulin, and hCG can differ in composition and activity from one preparation/batch to the next, so IU gives a consistent way to dose them across manufacturers.
 
Back
Top