Growth-Hormone Secretagogue Pharmacology: Hexarelin, GHRP-6, GHRP-2, CJC-1295 (DAC / No DAC), Ipamorelin / CJC-1295 Blend, IGF-1 LR3, MGF, PEG-MGF, Sermorelin, Tesamorelin, MK-677 — Full B2B Research Sourcing Guide

Research Guide | 2026-09-03 | 16 min read

Complete growth-hormone secretagogue research guide covering twelve molecules: Hexarelin, GHRP-6, GHRP-2, CJC-1295 (with and without DAC), CJC-1295 / Ipamorelin blend, IGF-1 LR3, MGF (Mechano Growth Factor), PEG-MGF, Sermorelin, Tesamorelin, and reference notes on MK-677. Includes GHS-R1a receptor signaling, pharmacokinetic half-life and dosing intervals, micro-purity HPLC expectations, and batch-level COA requirements.

Introduction: Mapping the GH axis for laboratory research

The growth-hormone (GH) axis is a multi-tiered signaling cascade: hypothalamic GHRH and ghrelin → pituitary somatotroph GH secretion → hepatic and local IGF-1 production → tissue-level IGF-1 receptor activation. To characterize any one node of this axis, the research laboratory needs pharmacology that can hit every adjacent node. This is why these twelve molecules are routinely sourced together under a single procurement dossier and why we publish a single integrated documentation anchor for the whole kit.

The molecules in this guide cluster into five mechanistic sub-families:

  • **GHS-R1a agonists (ghrelin receptor)**: Hexarelin, GHRP-6, GHRP-2, MK-677 (oral reference)
  • **GHRH analogs (GHRH receptor)**: Sermorelin, Tesamorelin, CJC-1295 No-DAC, CJC-1295 DAC
  • **Blended secretagogue combinations**: CJC-1295 / Ipamorelin blend
  • **Selective GHS-R1a agonists**: Ipamorelin
  • **Downstream IGF-1 effectors**: IGF-1 LR3, MGF, PEG-MGF

GHS-R1a Hexapeptide Family: Hexarelin, GHRP-6, GHRP-2

GHRP-6 (the founding synthetic GHS-R1a agonist)

GHRP-6 (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2, 873.0 Da) was the first synthetic hexapeptide GHS-R1a agonist, originally developed for diagnostic GH-pituitary testing. Its GH-release effect in rodents is dose-dependent, peaking at ~10 nmol/kg subcutaneous dosing. GHRP-6 also weakly stimulates appetite through central GHS-R1a signaling in the arcuate nucleus, which is one of the downstream effects researchers use to characterize it.

GHRP-2 (the more potent follow-up)

GHRP-2 (D-Ala-D-β-Nal-Ala-Trp-D-Phe-Lys-NH2, 891.4 Da) substitutes the N-terminal His of GHRP-6 with D-Ala-D-β-Nal, yielding a more potent and longer-acting GH release profile. The β-Nal (3-(2-naphthyl)-D-alanine) substitution improves receptor binding kinetics. GHRP-2 remains a popular research comparator to Hexarelin.

Hexarelin (the most potent, with unique downstream activity)

Hexarelin (His-D-Mrp-Ala-Trp-D-Phe-Lys-NH2, 887.0 Da) substitutes the D-Trp of GHRP-6 with D-Mrp (D-2-methyl-tryptophan). Hexarelin is the most potent of the three synthetic GHS-R1a hexapeptides in GH-axis research, and uniquely produces measurable prolactin and cortisol co-elevation. This distinguishes Hexarelin and makes it a useful probe for GHS-R1a off-target cross-talk and pituitary lactotroph effects.

Ipamorelin (the selective GHS-R1a comparator)

Ipamorelin (Aib-His-D-2-Nal-D-Phe-Lys-NH2, 711.9 Da) is a selective GHS-R1a agonist that does NOT elevate prolactin or cortisol. Ipamorelin produces clean GH-release kinetics and is therefore the standard reference peptide against which Hexarelin, GHRP-6, and GHRP-2 are compared when researchers need to disentangle GHS-R1a selective from GHS-R1a biased signaling.

CJC-1295 Family

CJC-1295 No-DAC

CJC-1295 No-DAC (30-amino-acid GHRH analog, 3365.9 Da) is the GHRH analog without the drug affinity complex (DAC). The four amino-acid substitutions that distinguish it from native GHRH (1-29) include: addition of Lys at the C-terminus to extend GHRH-(1-29) to GHRH-(1-30); and three stabilizing residues that block DPP-4 and plasmin cleavage. Plasma half-life is ~30-60 minutes.

CJC-1295 DAC

CJC-1295 DAC is the same 30-amino-acid core with an additional 7.6-kDa maleimidopropionic-acid-lysine conjugate attached at position 13. The DAC group binds covalently to circulating albumin via reactive thiol coupling and extends plasma half-life to ~5-7 days. The result is sustained GHRH receptor occupancy and continuous GH elevation, in contrast to the pulsatile pattern of CJC-1295 No-DAC and Sermorelin.

CJC-1295 / Ipamorelin Blend

The CJC-1295 No-DAC + Ipamorelin blend (CJC-1295 / Ipamorelin blend, 5:1 mass ratio is standard) is a research combination that pairs pulsatile GHRH receptor activation (No-DAC) with selective GHS-R1a agonism (Ipamorelin). The combination is widely used in animal growth-axis studies and is the most popular research peptide pairing for understanding synergistic hypothalamic-pituitary signaling.

GHRH-Analog Family: Sermorelin and Tesamorelin

Sermorelin is a 24-amino-acid synthetic GHRH-(1-29) analog (3357.9 Da) with a free acid N-terminus and amidated C-terminus (amide-28). It produces pulsatile GH release with a plasma half-life of ~10-20 minutes. Tesamorelin is a 44-amino-acid full-length GHRH analog (5135.9 Da) with an N-terminal trans-3-hexenoic acid cap that blocks DPP-4 and extends plasma half-life to 30-40 minutes. Tesamorelin is the research peptide with the closest pharmacology to endogenous GHRH signal kinetics.

Downstream IGF-1 Effectors: IGF-1 LR3, MGF, PEG-MGF

IGF-1 LR3

IGF-1 LR3 (Long R³ Insulin-like Growth Factor-1, 70-amino-acid, ~7.6 kDa) is an IGF-1 analog with Arg-3 / Arg-4 / Glu-9 substitutions that prevent IGFBP (IGF-binding-protein) binding. The result is dramatically reduced IGFBP buffering, extended in-vivo half-life to ~12-15 hours, and substantially increased IGF-1 receptor bioavailability. IGF-1 LR3 is the standard research tool for sustained IGF-1R activation in cell culture, in-vivo muscle physiology, and tissue-repair studies.

MGF (Mechano Growth Factor)

MGF is an IGF-1 splice variant (IGF-1Eb in humans, IGF-1Ec in rodents) expressed in skeletal muscle after mechanical loading or injury. Its unique C-terminal E-domain extension confers muscle-localized signaling with downstream kinetics biased toward satellite-cell proliferation rather than differentiation. The MGF C-terminal extension is recognized by anti-MGF-specific antibodies and verified through this route.

PEG-MGF

PEG-MGF is a pegylated form of MGF in which a 5-30 kDa PEG moiety is conjugated to the peptide. PEG-MGF extends plasma half-life from minutes to several hours and is used in research protocols requiring sustained MGF signaling without repeated dosing — particularly muscle-regeneration studies and satellite-cell activation time-course experiments.

Comparative Receptor and Pharmacokinetics Table

| Peptide | MW (Da) | Receptor | Half-life | GH peak characteristics | |---|---|---|---|---| | GHRP-6 | 873 | GHS-R1a | ~15-20 min | Moderate, transient | | GHRP-2 | 891 | GHS-R1a | ~30 min | High, transient | | Hexarelin | 887 | GHS-R1a | ~30-45 min | Highest, transient + cortisol/prolactin co-elevation | | Ipamorelin | 712 | GHS-R1a (selective) | ~2 h | Moderate, transient, NO cortisol/prolactin | | CJC-1295 No-DAC | 3366 | GHRH-R | ~30-60 min | Pulsatile | | CJC-1295 DAC | 10985 | GHRH-R | ~5-7 days | Sustained | | Sermorelin | 3358 | GHRH-R | ~10-20 min | Pulsatile (mirrors sleep-stage GH) | | Tesamorelin | 5136 | GHRH-R | ~30-40 min | Sustained pulsatile | | IGF-1 LR3 | 7600 | IGF-1R | ~12-15 h | Downstream effector | | MGF | 11.8 kDa | IGF-1R (E-domain) | ~5 min | Muscle-localized | | PEG-MGF | 17.8-42.8 kDa | IGF-1R (E-domain) | ~5 h | Sustained MGF signaling |

Quality Specifications Buyers Should Verify

Per-molecule COAs should document:

  • **HPLC purity** — ≥99% for hexapeptide GHS-R1a agonists, CJC-1295 variants, Sermorelin, Tesamorelin, IGF-1 LR3, MGF; ≥98% for PEG-MGF (pegylation heterogeneity is normal); ≥99% for Ipamorelin.
  • **Mass spectrometry identity** — measured mass within ±1 Da of theoretical for each defined peptide.
  • **DAC confirmation (CJC-1295 DAC only)** — maleimide-thiol binding assay or HPLC-fluorescent-tagged maleimide reaction to confirm DAC group is intact.
  • **PEG-homogeneity (PEG-MGF only)** — SDS-PAGE gel electrophoresis to confirm molecular weight and pegylation homogeneity (acceptable range 17-43 kDa, depending on PEG size).
  • **Counter-ion / salt form** — acetate or trifluoroacetate disclosed; TFA quantification.
  • **Endotoxin (LAL)** — <1 EU/mg for in-vitro biological work.
  • **Residual solvents** — acetonitrile and TFA below ICH Q3C.
  • **Lyophilization confirmation** — visual cake, moisture ≤5%, reconstitution note with sterile bacteriostatic water.

ZePeptide ships all twelve molecules (Hexarelin, GHRP-6, GHRP-2, CJC-1295 DAC, CJC-1295 No-DAC, CJC-1295 / Ipamorelin blend, Ipamorelin, IGF-1 LR3, MGF, PEG-MGF, Sermorelin, Tesamorelin) as lyophilized powders in 5-mg or 10-mg glass vials. Buyers sourcing the full secretagogue kit can request a single combined dossier.

Research-Use Disclaimers

All molecules in this guide are supplied strictly for laboratory research. GH-axis peptides (Sermorelin, Tesamorelin, CJC-1295 variants, Hexarelin, GHRP-6, GHRP-2, Ipamorelin), IGF-1 effectors (IGF-1 LR3, MGF, PEG-MGF), and the MK-677 reference compound are supplied for in-vitro, ex-vivo, and animal-model use only. IGF-1 LR3 and MGF are not supplied for human or animal administration outside regulated research protocols.

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Research Disclaimer: This guide compiles published peer-reviewed pharmacology and analytical-chemistry references. It is intended for laboratory scientists sourcing research-grade peptides for in-vitro, ex-vivo, and animal-model studies. No content here constitutes medical or veterinary advice.

Note: All research peptides listed in this guide are intended for laboratory research purposes only and are not for human or animal consumption. Buyers are responsible for institutional approvals, biosafety committee registration, and applicable import/export compliance for the destination country.

ZePeptide content is for lawful laboratory and in-vitro research sourcing. Products are not supplied for human or veterinary use.

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