What Is HGH 191AA? Growth Hormone Explained
| What it is | Recombinant human growth hormone |
|---|---|
| Length | 191 amino acids, a protein rather than a short peptide |
| Other names | Somatropin (INN), rhGH, hGH, GH |
| Receptor | Growth hormone receptor, directly |
| Main downstream mediator | IGF-1, produced by the liver |
| Why 191 is specified | Distinguishes it from an older 192 amino acid form with an extra methionine |
| Australian status | Prescription-only medicine |
| Supplied by PhaseOne | No, not currently. This page is reference material only |
Secretagogues vs supplying the hormone
| Secretagogues | HGH 191AA | |
|---|---|---|
| What is administered | A signalling peptide | The hormone |
| Pituitary involvement | Required | Not required |
| Release pattern | Works with the body's own rhythm | Set by the dose given |
| Size | 5 to 44 amino acids | 191 amino acids |
| Supplied by PhaseOne | Yes | No |
This is a reference page, not a product listing. PhaseOne does not currently supply HGH 191AA, and there is nothing to buy here. The page exists because HGH is the reference point the rest of the growth hormone axis is explained against, and several of our guides make more sense once you know what the hormone itself does.
HGH 191AA means recombinant human growth hormone with the full 191 amino acid sequence, the same length as the hormone the pituitary makes. It is also called somatropin and rhGH. This guide covers what it is, why the number 191 matters more than it looks, how supplying a hormone differs from asking the body to release it, its legal status in Australia, and what we supply instead.
On this page
What is HGH 191AA | Why 191 matters | Supplying vs asking | Where effects happen | Pulsatile release | Legal status in Australia | What we supply instead | FAQs
Key points at a glance
- PhaseOne does not currently supply HGH 191AA. This page is reference material only
- HGH 191AA is recombinant human growth hormone, 191 amino acids, matching the native sequence
- Also called somatropin, which is its international nonproprietary name, and rhGH in papers
- It is the hormone itself, not a peptide that prompts the body to release it
- Acts directly at the growth hormone receptor, so it does not need a working pituitary
- Much of what it does downstream runs through IGF-1 made by the liver
- Somatropin is a prescription-only medicine in Australia
- The 191 in the name distinguishes it from a 192 amino acid version with a real problem attached
- The compounds PhaseOne does supply in this axis are secretagogues and IGF-1 LR3
What is HGH 191AA?
Growth hormone is made by the anterior pituitary and is 191 amino acids long, which makes it a protein rather than a short peptide. Almost everything else discussed in these guides is between three and 44 residues; this is several times larger.
Recombinant means it is produced by engineered cells rather than extracted from tissue. That matters historically: growth hormone used to be collected from human pituitary glands post mortem, a practice that carried a serious contamination risk and was abandoned once recombinant production arrived in the early 1980s. Every modern reference to hGH means the recombinant kind.
| Property | HGH 191AA |
|---|---|
| What it is | Recombinant human growth hormone |
| Length | 191 amino acids |
| Other names | Somatropin (INN), rhGH, hGH, GH |
| Receptor | Growth hormone receptor, directly |
| Main downstream mediator | IGF-1, produced by the liver |
| Australian status | Prescription-only medicine |
| Supplied by PhaseOne | No, not currently |
Why the number 191 matters
It looks like pedantry in a product name and it is not. Early recombinant growth hormone was produced with 192 amino acids, carrying one extra methionine residue at the front that the native hormone does not have.
That single extra residue was enough to make the molecule more likely to provoke an immune response, because the body recognises it as not quite its own protein. Later production methods produced the true 191 sequence, and the 192 form fell out of use.
So when a listing says 191AA it is making a specific claim: that this is the native-length sequence rather than the older variant. That is worth verifying rather than assuming, and it is the reason the number appears in the name at all.
Supplying a hormone vs asking for it
This is the distinction that makes the rest of the growth hormone guides readable, and it is the real reason this page exists.
A secretagogue does not contain growth hormone. Ipamorelin and CJC-1295 work on receptors that tell the pituitary to release its own. Growth hormone itself skips all of that and arrives at the target receptor directly.
| Secretagogues | HGH 191AA | |
|---|---|---|
| What is administered | A signalling peptide | The hormone |
| Pituitary involvement | Required | Not required |
| Release pattern | Works with the body's own rhythm | Set by the dose given |
| Size | 5 to 44 amino acids | 191 amino acids |
| Supplied by PhaseOne | Yes | No |
The practical consequence for anyone reading research: a result obtained with a secretagogue does not automatically predict the same result from growth hormone, or the reverse. The upstream path differs entirely even though both end at the same receptor.
Where the effects actually happen
Growth hormone receptors are spread across many tissues, not concentrated in one organ, which is part of why the hormone has such a broad research literature.
The liver is the most important of them, because growth hormone prompts it to produce IGF-1, and IGF-1 carries a large share of the downstream tissue-level effects. This is why growth hormone research is so often measured through IGF-1 rather than through growth hormone levels themselves: the marker that moves last is the one that tells you something happened.
It is also why IGF-1 LR3 exists as a separate compound. If the question is specifically about the IGF-1 receptor, going straight there removes growth hormone and the liver from the experiment entirely.
Pulsatile release and why it matters
The pituitary does not release growth hormone at a steady rate. It comes in bursts, several times a day, with the largest usually during sleep.
Supplying the hormone directly produces a different shape entirely: one rise and one fall, on whatever schedule it was given. That is not a criticism, it is just a different exposure pattern, and it is one of the genuine reasons secretagogues and growth hormone are studied as separate things rather than as two ways of doing the same job.
For anyone comparing studies, it means sampling time relative to administration can change the reading substantially, and that two protocols with the same total amount can produce different curves.
Where it sits in the axis
Four stages, and growth hormone is the second.
| Stage | What acts there | Supplied by PhaseOne |
|---|---|---|
| Receptor signalling | GHRH and ghrelin receptor agonists | Ipamorelin, CJC-1295, Tesamorelin |
| The hormone | Growth hormone itself | No |
| Downstream mediator | IGF-1 analogue | IGF-1 LR3 |
The gap in the middle row is the honest picture of the range. We cover the stage above growth hormone and the stage below it, and not growth hormone itself. The growth hormone peptide guide sets the whole axis out in order.
Legal status in Australia
Somatropin is a prescription-only medicine in Australia. That is a materially different position from the research compounds covered elsewhere in these guides, which are unapproved rather than prescription-controlled.
Practically it means growth hormone is not something a research supplier can reasonably offer, and a listing that appears to offer it should raise a question rather than close a sale. It is also why this page carries no pricing, no vial sizes and no reconstitution instructions: none of that would be appropriate here.
If you have a clinical question about growth hormone, that is a conversation for a doctor or pharmacist, not a research supplier, and not this page.
Why PhaseOne does not supply it
We used to. We do not currently, and this page previously said otherwise, which was wrong and is now corrected.
No pricing, no stock and no certificate of analysis exist for HGH 191AA at PhaseOne, because there are no batches. Any claim to the contrary that you find in an older cache or a third-party listing is out of date.
The page stays because the explanation is still useful. Understanding what growth hormone does is what makes the secretagogues comprehensible, and taking the page down would leave several of our other guides referring to something unexplained.
What PhaseOne supplies instead
Three stages of the same axis, minus the hormone in the middle.
| If the question is | The compound | What it does |
|---|---|---|
| Can the pituitary be prompted to release more | Ipamorelin | Ghrelin receptor secretagogue, selective |
| Same, via the other receptor | CJC-1295 No DAC | GHRH analogue, shortened fragment |
| Same, closest to the natural signal | Tesamorelin | Full length GHRH analogue |
| Both receptors at once | CJC-1295 and Ipamorelin blend | Two independent inputs, one vial |
| What does the IGF-1 receptor do on its own | IGF-1 LR3 | Downstream mediator, acts directly |
Browse Ipamorelin , CJC-1295 No DAC , Tesamorelin , the CJC-1295 and Ipamorelin blend or IGF-1 LR3 , or the full research range .
If you are reading HGH research
Two cautions that apply to the literature rather than to any product.
- Most of the human growth hormone literature comes from clinical research in specific patient populations with specific protocols. It does not generalise cleanly to other questions, and it is the most over-quoted body of work in this whole category.
- Check whether a source is describing the 191 or the 192 amino acid form, especially anything written before the mid 1980s or anything citing older work. They are not the same molecule and the immune response differs.
For how purity and identity get verified in general, the HPLC testing guide and the research standards guide apply to any compound, including ones we do not sell.
Related research guides
For the secretagogues, the Ipamorelin guide , the CJC-1295 guide , the Tesamorelin guide and the CJC-1295 and Ipamorelin guide . For the downstream mediator, the IGF-1 LR3 guide . For the axis in order, the growth hormone peptide guide . For handling the compounds we do supply, the reconstitution guide and storage guide .
Frequently Asked Questions
Does PhaseOne sell HGH 191AA?
No, not currently. This page is reference material rather than a listing. There is no pricing, no stock and no certificate of analysis for it, because there are no batches. We previously supplied it and do not at the moment.
What is HGH 191AA in simple terms?
Recombinant human growth hormone with the full 191 amino acid sequence, matching the hormone the pituitary produces. It is also called somatropin and rhGH.
Is HGH 191AA the same as somatropin?
Yes. Somatropin is the international nonproprietary name for recombinant human growth hormone. HGH, hGH, rhGH and GH all refer to the same thing in general use.
Why does the name say 191AA?
Because early recombinant growth hormone was made with 192 amino acids, one extra methionine at the front that the native hormone does not have. That extra residue made it more likely to provoke an immune response. The 191 label claims the native-length sequence.
Is the 192 amino acid version still around?
It fell out of use once the true 191 sequence could be produced. It still matters when reading older literature, because a study on the 192 form is not a study on the same molecule.
Is HGH a peptide?
Technically it is a protein. At 191 amino acids it is several times longer than anything else discussed in these guides, which are mostly between three and 44 residues.
How is HGH different from Ipamorelin or CJC-1295?
A secretagogue contains no growth hormone. It acts on a receptor that prompts the pituitary to release its own. Growth hormone skips that entirely and arrives at the target receptor directly, so it does not need a working pituitary.
Can a secretagogue result be applied to growth hormone, or the reverse?
Not reliably. The upstream path differs completely even though both end at the same receptor, so one does not predict the other.
Why is IGF-1 always mentioned alongside growth hormone?
Because growth hormone prompts the liver to make IGF-1, and IGF-1 carries a large share of the downstream tissue effects. That is why growth hormone research is often measured through IGF-1 rather than growth hormone levels.
What does pulsatile release mean here?
The pituitary releases growth hormone in bursts several times a day rather than at a steady rate, with the largest usually during sleep. Supplying the hormone produces a single rise and fall instead, which is a different exposure pattern.
Is HGH legal in Australia?
Somatropin is a prescription-only medicine in Australia. That is a different position from the unapproved research compounds covered elsewhere in these guides, and it is why a research supplier cannot reasonably offer it.
Where can I buy HGH 191AA in Australia?
Not from PhaseOne. It is a prescription-only medicine here, so that is a question for a doctor or pharmacist rather than a research supplier. Any listing that appears to offer it should raise a question.
Why has this page got no vial sizes or reconstitution table?
Because we do not supply the compound, and none of that would be appropriate on a reference page for a prescription-only medicine.
Why keep the page at all?
Because growth hormone is the reference point the secretagogues are explained against. Several of our other guides describe their compounds by contrast with the hormone itself, and removing this page would leave that unexplained.
What does PhaseOne supply in this axis instead?
Ipamorelin and CJC-1295 No DAC and Tesamorelin at the receptor stage above growth hormone, the CJC-1295 and Ipamorelin blend, and IGF-1 LR3 at the mediator stage below it.
Which of those is closest to growth hormone itself?
None of them is growth hormone. Tesamorelin is the closest to the natural signal that triggers its release, and IGF-1 LR3 is the closest to the mediator that carries out much of its effect. Neither is a substitute.
Was HGH 191AA ever supplied by PhaseOne?
Yes, previously. It is not part of the current range. An older page described it as supplied, which was out of date and has been corrected.
Should I trust older claims about PhaseOne HGH stock?
No. If you find a cached page or a third-party listing saying we stock it, that is out of date. There is no current stock and no certificate for it.
Disclaimer
This page is provided as reference information only and does not describe a product supplied by PhaseOne. All products PhaseOne does supply are intended strictly for laboratory research purposes only, and are not intended for human consumption, therapeutic use, cosmetic use, veterinary use, or diagnostic applications.
