✓ Medically reviewed by  ·  Last reviewed: May 2026

Morgan Ellis

Pharmacy Researcher · 8 years experience

Pharmacy researcher with 8 years reviewing clinical drug information, generic formulation equivalence, and international pharmaceutical standards. Focuses on patient-facing accuracy in medication education.

Best Growth Hormone Peptides: 10 GHRH Analogues, GHRPs, and HGH Compounds Compared

The growth-hormone axis is the single most-researched signalling pathway in peptide pharmacology. Endogenous GH release is gated by the pituitary somatotroph, which carries two distinct receptor families: the GHRH receptor (activated by hypothalamic growth-hormone-releasing hormone) and the GHS-R1a receptor (activated by the gut-secreted hormone ghrelin and a class of synthetic peptides called GHRPs / growth-hormone-releasing peptides). Co-activation of both receptors produces a synergistic GH pulse larger than either alone — which is why the canonical research stack pairs a GHRH analogue with a GHRP.

Of the 39 research peptides on the MedsBase peptide catalogue, 10 act directly on the GH axis. They are listed below by mechanism class and research priority.

How to use this hub

Each pick below carries: mechanism class (GHRH analogue / GHRP / downstream), the pituitary receptor it binds, comparator drug status, manufacturer, link to the product page, and a “pick for” research scenario.

• Pure GHRH research: Sermorelin (the shortest GHRH fragment that retains full activity), CJC-1295 (both DAC variants), Tesamorelin (the long-acting clinical-grade GHRH analogue).
• GHRP / ghrelin-mimetic research: Ipamorelin (selective), GHRP-2 (mixed), GHRP-6 (with appetite-stimulation arm).
• Downstream / readout compounds: HGH 191AA (recombinant somatropin itself), HGH Fragment 176-191 (lipolysis-selective C-terminal fragment), IGF-1 LR3 (the downstream anabolic mediator).
• Synergistic stacking: CJC-1295 + Ipamorelin is the reference stack.

1. Ipamorelin (cleanest-selectivity GHRP)

Mechanism class: GHS-R1a agonist (selective) · View product

Ipamorelin is the GHRP that established the modern “selective” GHRP class. Earlier GHRPs (GHRP-2, GHRP-6, hexarelin) retain measurable activity at neighbouring receptors — producing cortisol and prolactin elevation alongside the desired GH pulse. Ipamorelin’s pentapeptide architecture binds GHS-R1a with high selectivity and minimal cross-reactivity, producing a clean GH pulse without HPA-axis activation. This makes it the GHRP of choice for research scenarios where cortisol confounding would compromise endpoint interpretation. Typical research-protocol dose is 100-300 mcg per administration, often pre-sleep to align with the endogenous GH pulse.

Pick for: GH-axis research where cortisol/prolactin confounding must be eliminated; the GHRP arm of any synergistic stack.

2. CJC-1295 without DAC (Mod-GRF 1-29 — short-acting GHRH analogue)

Mechanism class: GHRH receptor agonist (short-acting) · Half-life: ~30 minutes · View product

CJC-1295 without DAC — also known as Mod-GRF 1-29 — is the 29-amino-acid GHRH analogue carrying four amino-acid substitutions that confer enzymatic resistance without extending half-life beyond the natural ~30-minute window. The short half-life is the point: it produces sharp pulsatile GH release approximating the endogenous pulsatility pattern, rather than sustained elevation. Pre-sleep dosing (typically 100 mcg) aligns the research pulse with the natural overnight GH peak. This is the GHRH analogue used in the classical CJC-1295 + Ipamorelin synergy stack.

Pick for: research protocols that need to preserve natural GH pulse-pattern; the GHRH arm of synergistic stacks where pulse fidelity matters more than sustained levels.

3. CJC-1295 with DAC (long-acting GHRH analogue)

Mechanism class: GHRH receptor agonist (long-acting, albumin-conjugated) · Half-life: ~6-8 days · View product

The “DAC” (Drug Affinity Complex) is a maleimidopropionyl group that lets the peptide bind covalently to circulating albumin, extending half-life from minutes to days. The trade-off is loss of pulsatility — instead of sharp peaks, with-DAC CJC-1295 produces a sustained “GH bleed” elevation across days. For research scenarios where the goal is total GH/IGF-1 exposure rather than pulse-pattern fidelity, with-DAC is the choice. Weekly dosing protocols are common in the research literature.

Pick for: research protocols measuring chronic elevated GH/IGF-1 exposure; sustained-elevation models; convenience-driven protocols where daily dosing is impractical.

4. Tesamorelin (long-acting GHRH analogue; comparator Egrifta)

Mechanism class: GHRH analogue · Comparator drug: Egrifta (FDA-approved 2010 for HIV-associated lipodystrophy) · View product

Tesamorelin is the only GHRH analogue with an FDA-approved comparator drug. Egrifta is approved specifically for visceral adipose tissue reduction in HIV-associated lipodystrophy — and the regulatory data (LIPO-1 / LIPO-2 trials) demonstrated mean -15.2% VAT reduction at 26 weeks. The molecule retains pulsatile pituitary stimulation but the formulation supports daily dosing with relatively stable plasma exposure. Beyond HIV-LD, tesamorelin is studied in non-HIV abdominal-obesity research, NAFLD/NASH protocols, and as a comparator in GHRH-axis mechanism work.

Pick for: visceral-fat-specific research; the regulatory-precedent GHRH analogue; protocols where clinical-grade comparator data is needed.

5. Sermorelin (GRF 1-29 — the prototype GHRH fragment)

Mechanism class: GHRH analogue (truncated, the minimal active sequence) · View product · Full research guide

Sermorelin is the 29-amino-acid truncation of native GHRH (the full molecule is 44 amino acids; sermorelin retains 100% of the receptor-binding activity in the first 29 residues). It is the molecule that established the principle that GHRH activity can be reduced to a short, peptide-synthesizable sequence — making it both the historical prototype and the still-used reference compound for GHRH-pulse research. Half-life is short (similar to native GHRH at ~10-15 minutes); research dosing is typically subcutaneous pre-sleep at 100-300 mcg. Sermorelin is the most cost-effective GHRH analogue for academic research where the longer-acting CJC variants are not needed.

Pick for: baseline GHRH-pulse research; the comparator/reference compound in GHRH mechanism work; cost-effective pure-GHRH studies.

6. GHRP-2 Acetate (mixed-receptor GHRP)

Mechanism class: GHS-R1a agonist (with measurable cortisol/prolactin side activity) · View product

GHRP-2 is a hexapeptide ghrelin mimetic developed before the more-selective Ipamorelin. The molecule produces a strong GH pulse (somewhat larger than Ipamorelin in head-to-head research) but retains measurable activity on the cortisol and prolactin axes — a confounding factor for some research endpoints. The trade-off is depth-of-pulse vs cleanness. For research scenarios where maximum GH amplitude matters and the additional pituitary axes are not endpoints, GHRP-2 is the more potent option.

Pick for: maximum-GH-pulse research where ipamorelin’s gentler effect is insufficient; legacy-comparator work referencing the older GHRP class.

7. GHRP-6 Acetate (with appetite-stimulation activity)

Mechanism class: GHS-R1a agonist (with significant orexigenic activity) · View product

GHRP-6 carries the same ghrelin-mimetic GH pulse as GHRP-2 but with a substantially larger appetite-stimulation effect — reflecting ghrelin’s natural dual role as both a GH secretagogue and an orexigenic signal. This is GHRP-6’s distinguishing research feature. Protocols studying appetite/feeding behaviour, or research models where caloric intake stimulation is an endpoint (e.g., cachexia or undernutrition research), use GHRP-6 specifically for the orexigenic arm. Cortisol/prolactin elevation is similar to GHRP-2.

Pick for: appetite / feeding-behaviour research; cachexia research models; dual GH/orexigenic-arm studies.

8. HGH 191AA (recombinant somatropin — the downstream comparator)

Mechanism class: Recombinant human growth hormone (full-length, 191 amino acids) · CAS: 12629-01-5 · View product

HGH 191AA is recombinant human growth hormone itself — the full-length 191-amino-acid molecule produced by E. coli expression systems. It is the downstream effector that GHRH analogues and GHRPs aim to release endogenously. Including HGH 191AA in this hub matters because it is the canonical comparator molecule for any GH-axis research — the question “did the GHRH analogue produce GH elevation equivalent to direct administration of HGH?” requires the direct-administration arm as control. This is a substantially larger and more complex molecule than the synthetic peptides above; storage and reconstitution protocols are more demanding (multi-step reconstitution at lower concentrations, strict 2-8 °C storage, no freeze-thaw of the reconstituted solution).

Pick for: control-arm research for GHRH-analogue or GHRP studies; direct exogenous-GH protocols where endogenous pulse mimicry is not the question.

9. HGH Fragment 176-191 (lipolysis-selective C-terminal fragment)

Mechanism class: 16-amino-acid C-terminal GH fragment, lipolysis-selective · View product

HGH Fragment 176-191 is the molecular dissociation experiment in peptide form: the C-terminal 16 residues of full-length GH retain the lipolytic activity (mediated through hormone-sensitive lipase activation in adipocytes) but lack the growth-promoting, IGF-1-elevating, and insulin-resistance-inducing effects of the full molecule. For research scenarios where you want GH’s fat-mobilisation effect without its anabolic / metabolic side-effect profile, the fragment isolates that single arm. Studied protocols use substantially smaller doses than full-length GH.

Pick for: isolated-mechanism lipolysis research; protocols where IGF-1 elevation must be avoided; preclinical models of selective fat mobilisation.

10. IGF-1 LR3 (the downstream anabolic mediator)

Mechanism class: Long-arginine analogue of insulin-like growth factor-1 · View product · Full research guide

IGF-1 LR3 sits downstream of GH in the somatotropic axis — it is the molecule through which most of GH’s anabolic effects are mediated. The “LR3” suffix refers to a long-arginine variant: a 13-amino-acid N-terminal extension and an arginine substitution at position 3 that reduces IGFBP binding, extending plasma half-life from native IGF-1’s ~10 minutes to ~20 hours. The longer half-life is a research-grade feature — direct IGF-1 administration would clear too quickly to support meaningful study. Including IGF-1 LR3 in this hub matters because GH-axis research often needs to dissociate central (GH-pulse) effects from peripheral (IGF-1-mediated) effects; direct IGF-1 LR3 administration provides the peripheral-arm control.

Pick for: peripheral-vs-central GH-axis research; IGF-1-specific mechanism studies; downstream-arm controls in GHRH/GHRP experiments.

Comparison table

The classical synergy stack: CJC-1295 + Ipamorelin

The defining research stack of the modern GH-peptide literature pairs one GHRH analogue with one GHRP. The mechanistic logic: GHRH increases the pool of GH available for release by stimulating somatotroph synthesis and basal release; the GHRP triggers the actual release pulse. Activating both pathways together produces a GH pulse substantially larger than either alone — the published literature shows roughly 2-3x amplification compared with monotherapy at matched doses.

The canonical protocol pairs CJC-1295 without DAC (100 mcg) with Ipamorelin (100 mcg), both subcutaneous, both pre-sleep. The pre-sleep timing aligns the synthetic pulse with the natural overnight GH peak. The “without DAC” choice preserves natural pulsatility — the goal is to amplify the existing pulse, not to flatten it.

For an in-depth breakdown of the stack mechanism and research-protocol design, see the CJC-1295 + Ipamorelin complete stack guide and the stack mechanism deep-dive.

Frequently asked research questions

Why is the CJC-1295 + Ipamorelin combination always the recommended stack?

Because each addresses a different receptor on the same pituitary cell. CJC-1295 (a GHRH analogue) binds the GHRH receptor; Ipamorelin (a GHRP) binds the GHS-R1a (ghrelin) receptor. Co-activation produces synergistic GH release substantially larger than either compound alone — published research shows 2-3x amplification. The “without DAC” CJC-1295 variant is preferred for stacking because its short half-life preserves natural pulsatility, which is what the synergy is amplifying.

What is the difference between CJC-1295 with DAC and without DAC?

DAC (Drug Affinity Complex) is a maleimidopropionyl group that lets the peptide bind covalently to circulating albumin, extending half-life from approximately 30 minutes to roughly 6-8 days. Without-DAC CJC-1295 produces sharp pulsatile GH release; with-DAC CJC-1295 produces sustained “GH bleed” elevation across days. Pick based on whether your research model needs pulse-pattern fidelity (without-DAC) or chronic-exposure modelling (with-DAC).

Is Ipamorelin really cleaner than GHRP-2 and GHRP-6?

Yes — this is well-documented in the GHRP class literature. GHRP-2 and GHRP-6 retain measurable cortisol and prolactin axis activity in addition to their GH-releasing effect, reflecting structural similarity to ACTH-class signalling. Ipamorelin’s pentapeptide architecture is selective for GHS-R1a and shows essentially no cortisol or prolactin elevation in published studies. For research endpoints where HPA-axis or lactotroph activation would confound interpretation, Ipamorelin is the unambiguously correct choice.

Is Tesamorelin meaningfully different from Sermorelin?

Both are GHRH analogues that bind the same receptor. The differences: Tesamorelin carries an N-terminal trans-3-hexenoyl modification that confers enzymatic stability without changing the receptor binding profile, supporting daily-dose protocols with stable plasma levels. Sermorelin is the unmodified 1-29 GHRH fragment with very short half-life (~10-15 min), used historically as a pulse-research compound. Tesamorelin is also the only one with an FDA-approved comparator drug (Egrifta) — which means the regulatory-grade clinical data exists for it but not for sermorelin.

What’s the role of HGH 191AA in a peptide-research catalogue?

As the direct-administration control. GHRH-analogue and GHRP research aims to elevate endogenous GH; the only way to validate that the elevation reaches a target plasma concentration is to compare against direct GH administration. HGH 191AA is recombinant somatropin — the molecule the peptides are working to release endogenously. Research scenarios that need a direct-GH control arm (rather than an endogenous-pulse model) use HGH 191AA as the standalone or comparator compound.

How does HGH Fragment 176-191 differ from full-length HGH 191AA?

The fragment is the C-terminal 16 amino acids of the full molecule. It retains the lipolytic activity of GH (acting on adipocyte hormone-sensitive lipase) but lacks the somatomedin-axis effects: no IGF-1 elevation, no growth-promoting action, no insulin-resistance induction. For research scenarios that want GH’s fat-mobilisation effect without its broader metabolic profile, the fragment isolates that single arm. Note: clinical / Phase 2 development of HGH Fragment was discontinued years ago for human therapy; it remains a research compound only.

Where does IGF-1 LR3 fit in GH-axis research?

Downstream. The somatotropic axis is GHRH/GHRP → GH → IGF-1. GH itself has both direct receptor-mediated effects (e.g. lipolysis) and indirect effects mediated through IGF-1 (most anabolic outcomes). To dissect direct-GH vs IGF-1-mediated effects in research, you need a direct IGF-1 administration arm — which is what IGF-1 LR3 provides, with a half-life long enough (~20 hours) to support meaningful study unlike native IGF-1’s ~10-minute window.

Are there safety concerns with sustained GH/IGF-1 elevation in research models?

Yes. The literature documents (a) insulin-resistance effects with sustained elevation, (b) fluid retention and arthralgia in research subjects receiving exogenous GH or strong GHRH/GHRP stimulation, (c) theoretical concerns around any pre-existing malignancy since GH/IGF-1 are mitogenic signals, and (d) acromegaly-like soft-tissue changes with very-long-duration high-dose exposure. These considerations are research-protocol design factors, not safety markers for human therapeutic use (which these compounds are not approved for).

Bottom line

The GH-axis peptide cluster is organised cleanly by mechanism. For pure GH-pulse research, the CJC-1295 + Ipamorelin stack is the reference, with Sermorelin as the baseline GHRH compound. For clinical-precedent work, Tesamorelin is the only FDA-approved-comparator option. For sustained exposure, CJC-1295 with DAC. For amplitude over selectivity, GHRP-2 (and GHRP-6 for the orexigenic arm specifically). For downstream-arm controls, HGH 191AA (direct GH) and IGF-1 LR3 (peripheral mediator). For dissociating GH’s lipolytic effect from its anabolic effect, HGH Fragment 176-191. The 10 compounds together cover essentially every research scenario in modern GH-axis pharmacology.

Written by

Sophie Chen

Pharmaceutical Content Researcher · 8 years experience

Sophie Chen is a pharmaceutical content researcher with 8 years covering generic medication access and clinical pharmacology. She specialises in international regulatory frameworks, bioequivalence standards, and patient-facing education on therapeutic drug classes. She is not a clinician.