Search traffic and forum language treat GH peptides as one object. The primary literature does not. There are at least two receptor classes in common research-chemical circulation, a third intervention (recombinant GH) that is a licensed medicine, and a wide spread of evidence grades across compounds that are routinely discussed together.

This explainer is not a protocol. It does not describe how to prepare, combine or administer any of these substances. None of the unlicensed secretagogues discussed here is an MHRA-authorised medicine. No consumption or self-administration advice.

1. Two receptors, not one category

  • GHRH acts at the GHRH receptor (Gs-coupled). Analogues: sermorelin (GHRH 1-29), somatorelin (GHRH 1-44), CJC-1295 (with or without DAC), tesamorelin.
  • Ghrelin acts at GHS-R1a. Synthetic agonists: GHRP-6, GHRP-2, hexarelin, ipamorelin.

In pituitary preparations the two ligands can produce more GH release together than either alone. That is somatotroph pharmacology, not a clinical protocol, safety file or regulatory status. Somatostatin tone, nutritional state and assay timing matter; a single GH peak is easy to over-interpret.

2. Class A — GHRH-receptor analogues

Sermorelin: short half-life; historical diagnostic and early therapeutic use; old human evidence; not a current UK-licensed GH-replacement product.

CJC-1295: DAC variant extends half-life via albumin binding; non-DAC (mod GRF 1-29) remains short-acting. Human work is early PK/PD only. Evidence grade limited.

Tesamorelin: outlier — completed programme for HIV-associated excess visceral adipose tissue; Egrifta authorised in other jurisdictions. That package does not transfer a UK marketing authorisation and does not upgrade sermorelin, CJC-1295 or the GHRP class. Cite the HIV-lipodystrophy trials, not a generic GH-peptide benefit.

Somatorelin: diagnostic/historical; not a substitute for tesamorelin’s trial package.

3. Class B — GHS-R1a agonists

GHRP-6: early hexapeptide; appetite and gastric effects; ACTH/cortisol movement. GHRP-2: more potent GH release; still less ACTH-selective than ipamorelin. Hexarelin: potent; cardiac GHS-R and ACTH findings. Ipamorelin: Novo Nordisk pentapeptide (Raun 1998); human PK/PD; Beck 2014 ileus study produced no licensed drug.

Class B grade: limited beyond acute GH release. No incretin-style Phase 3 programme. WADA prohibits GH secretagogues in sport — a sporting rule, not an MHRA schedule.

4. What synergy is allowed to mean

Permissible: the two receptors converge on somatotroph GH release; experimental designs should control each ligand separately and together. Impermissible: that a research-chemical combination is an evidence-based regimen; that IGF-1, body composition, injury repair or sleep will move predictably in humans; that combination use has a characterised safety file. No combination cycles, injection schedules or reconstitution recipes for human use.

5. Recombinant GH is a different object

Somatropin is a licensed UK POM with defined indications and an SmPC. Secretagogues are not a legal or pharmacological substitute. An endogenous GH pulse after ipamorelin is not interchangeable with somatropin-replacement outcomes.

6. UK regulatory position

Sermorelin, CJC-1295, ipamorelin, GHRP-2, GHRP-6, hexarelin and unlicensed tesamorelin: no UK marketing authorisation; supply with medicinal claims engages the Human Medicines Regulations 2012 and Medicines Act 1968; not, on current public lists, MDA Schedule 1–5; MHRA 2026 research-peptide labelling guidance applies; WADA prohibition is independent of MHRA classification. Tesamorelin’s overseas product licence is not a UK POM listing.

7. Grade map

Tesamorelin: higher grade for its published indication in studied jurisdictions; UK research-chemical supply remains grey. Ipamorelin, CJC-1295, sermorelin, GHRP-2, GHRP-6, hexarelin: limited beyond acute GH release. Somatropin: licensed POM, not graded here. Grades move only on peer-reviewed human data or a UK regulatory decision.

8. Reading rules

  1. Name the receptor (GHRH vs GHS-R1a) or distrust the claim. 2. Separate PK from outcomes. 3. Do not cite pharmaceutical tesamorelin as if it were a research-chemical GHRP. 4. Discard equivalence to somatropin. 5. Discard human-use doses, reconstitution volumes or injection sites.

This article is AI-researched and editorially reviewed. It is provided for research and educational purposes only and is not medical advice. Research peptides are not licensed for human consumption in the UK.