Research-use information only. This page summarises published literature on human growth hormone and growth-hormone-related research peptides. Material supplied by Peptides Lab UK is for laboratory research use only, not for human or veterinary use, and nothing here is medical or dosing advice.
“HGH peptides” is an umbrella term covering two quite different research categories: recombinant human growth hormone itself (somatropin, the 191-amino-acid sequence), and the much larger family of growth-hormone secretagogues that stimulate the body’s own GH release rather than supplying it directly. Understanding which category a compound belongs to is the first thing any growth-hormone research protocol has to establish, because the two work through entirely different mechanisms.
The two categories, clearly separated
- Recombinant HGH (somatropin, HGH 191AA) — this is growth hormone itself, the full 191-amino-acid sequence produced by recombinant technology. It acts directly on growth hormone receptors throughout the body. See HGH 191AA.
- Growth-hormone secretagogues — these do not supply GH. They stimulate the pituitary to release its own, and they split further into two mechanisms below.
The practical distinction: recombinant HGH raises growth hormone regardless of pituitary function, while secretagogues depend on a working pituitary and preserve the natural pulsatile release pattern.
The two secretagogue mechanisms
Within the secretagogue category, compounds act through one of two receptor systems — and combination research protocols typically pair one from each because they act synergistically:
- GHRH analogues — mimic growth-hormone-releasing hormone. This group includes sermorelin, CJC-1295 and tesamorelin.
- Ghrelin mimetics / GHS-R agonists — act on the ghrelin receptor. This group includes ipamorelin, GHRP-6, hexarelin and the orally active MK-677 (ibutamoren).
The reason combinations such as CJC-1295 with ipamorelin are so heavily studied is that a GHRH analogue and a ghrelin mimetic activate two separate pathways that amplify each other’s effect on GH release.
How growth hormone acts downstream
Whichever route raises GH, much of its anabolic effect is mediated not directly but through insulin-like growth factor 1 (IGF-1), produced mainly by the liver in response to GH. This is why IGF-1 and its analogues are studied alongside the GH axis — see our IGF-1 LR3 research guide. A complete picture of growth-hormone research has to account for the GH → IGF-1 relationship rather than treating GH in isolation.
Related fragments and adjacent compounds
Some research compounds derive from the GH molecule without reproducing its full activity. AOD-9604 is a fragment of the C-terminus of GH studied for metabolic rather than growth-promoting activity. Menotropin (HMG) supplies gonadotropins rather than GH and belongs to a different axis entirely — see HMG — but is sometimes confused with the GH group.
Choosing a research approach
The choice between direct recombinant HGH and a secretagogue is a study-design decision. Direct HGH gives a defined, GH-receptor-level input independent of the pituitary; secretagogues preserve physiological pulsatility and feedback, which matters for studies of the axis itself. Neither is “better” — they answer different questions, and conflating them produces uninterpretable results.
Handling and dosage
Recombinant HGH is measured in international units as well as milligrams, reflecting bioactivity standardisation, and as a large protein it is more handling-sensitive than short peptides. Secretagogues are mostly short peptides reconstituted in bacteriostatic water; MK-677 is an orally active non-peptide. Published protocols vary widely by compound and endpoint and describe research documentation only, not instructions for human use. See our bacteriostatic water guide for reconstitution mechanics.
The UK regulatory position
Somatropin is a prescription-only medicine in the UK when supplied for human use; the secretagogues are not licensed medicines. Peptides Lab UK supplies all of these for laboratory research only, correctly labelled, not for human or veterinary use. Because recombinant HGH is a large protein whose integrity is not visually assessable, batch-specific analytical data matters especially — see our quality-standards SOP.
Frequently asked questions
What are HGH peptides?
An umbrella term covering recombinant human growth hormone itself (somatropin, 191 amino acids) and the growth-hormone secretagogues that stimulate the body’s own GH release. They work through different mechanisms.
What is the difference between HGH and a growth-hormone secretagogue?
Recombinant HGH supplies growth hormone directly and works regardless of pituitary function. Secretagogues stimulate the pituitary to release its own GH, depend on a working pituitary and preserve natural pulsatile release.
What are the two types of secretagogue?
GHRH analogues (sermorelin, CJC-1295, tesamorelin) and ghrelin mimetics / GHS-R agonists (ipamorelin, GHRP-6, hexarelin, MK-677). Combination research pairs one from each because they act synergistically.
How does growth hormone relate to IGF-1?
Much of GH’s anabolic effect is mediated through IGF-1, produced mainly by the liver in response to GH. GH research is usually interpreted alongside the GH → IGF-1 relationship.
Is HGH 191AA a peptide?
It is recombinant human growth hormone — a 191-amino-acid protein. Larger and more handling-sensitive than the short-peptide secretagogues.
Is HGH legal in the UK?
Somatropin is a prescription-only medicine for human use in the UK; the secretagogues are not licensed medicines. Supply for laboratory research, correctly labelled, is a separate lawful category.
Disclaimer: this content is for educational and research purposes only. None of the compounds described are intended for human or veterinary use.
