Sermorelin vs CJC-1295 vs Modified GRF 1-29: A GHRH Analog Comparison
Three of the most commonly-discussed GHRH analog peptides for endogenous GH and IGF-1 elevation. Here's how they differ, which fits which use case, and what the evidence supports.
The 60-second version
All three are GHRH analogs that stimulate the pituitary to release growth hormone. Sermorelin is shortest-acting (FDA-approved diagnostic, sometimes compounded). CJC-1295 with DAC is longest-acting (research-grade, 6-8 day half-life via albumin binding). Modified GRF 1-29 is CJC-1295 without DAC — same active sequence with ~30 minute half-life for pulsatile dosing. Choice depends on whether you want pulsatile GH release (mimicking natural physiology — Sermorelin or Mod GRF) or sustained tonic elevation (CJC with DAC). Community preference has shifted toward pulsatile dosing.
Key takeaways
- All three are GHRH analogs that stimulate pituitary GH release.
- Sermorelin: shortest half-life, FDA-approved diagnostic, limited compounding access.
- Modified GRF 1-29: short half-life, research-grade, pulsatile dosing.
- CJC-1295 with DAC: 6-8 day half-life, sustained tonic stimulation, weekly dosing.
- Pulsatile dosing more closely mimics natural physiology.
- Tonic dosing provides convenience but overrides natural feedback patterns.
- Modified GRF 1-29 + ipamorelin is the most-discussed community stack.
- Phase 1 PK validates GH/IGF-1 elevation; Phase 2/3 outcome data is absent.
The core distinction: pulsatile vs. tonic
Your body naturally releases growth hormone in pulses — discrete bursts most prominent at night during deep sleep. Pulsatile pattern matters because GH receptors can downregulate with sustained high exposure, different physiological effects emerge from pulses vs. sustained elevation, and the body's feedback systems are designed for pulses.
Sermorelin (short half-life): pulses similar to natural GHRH. Modified GRF 1-29 (short half-life): pulses, often timed to bedtime. CJC-1295 with DAC (multi-day half-life): tonic, sustained elevation.
Sermorelin profile
29-amino-acid synthetic peptide containing the active fragment of human GHRH. FDA-approved as Geref (no longer marketed) for diagnostic testing. Half-life: 10-20 minutes. Typical dose: 100-500 mcg SC at bedtime. Strengths: closest to natural GHRH pharmacology, pulsatile profile preserves feedback regulation, some FDA-approval history. Limitations: no longer commercially available as finished pharmaceutical, depends on compounding pharmacy access (constrained), daily dosing burden, modest effect magnitude.
Modified GRF 1-29 profile
Same modified GHRH(1-29) sequence as CJC-1295 but without the maleimidopropionic acid linker that produces multi-day albumin binding. Half-life: ~30 minutes. Typical dose: 100-200 mcg SC at bedtime, often stacked with ipamorelin. Strengths: pulsatile profile, modified sequence's improved protease resistance, cleanly paired with ipamorelin for synergistic GH release through two pathways. Limitations: research-grade only, source quality varies, daily dosing, effect depends on appropriate timing.
CJC-1295 with DAC profile
Modified GRF 1-29 sequence with maleimide linker that binds peptide to circulating albumin, extending half-life to 6-8 days. Typical dose: 1-2 mg SC once or twice weekly. Strengths: sustained GH/IGF-1 elevation, weekly convenience, Phase 1 PK data (Teichman 2006) demonstrates reliable IGF-1 elevation. Limitations: tonic stimulation overrides natural pulsatile pattern, concerns about receptor desensitization, Phase 2 program discontinued after unexplained death in unrelated trial.
Which fits which use case
Physiologic-style GH release: Sermorelin (if accessible) or Modified GRF 1-29 (research-grade).
Maximum convenience: CJC-1295 with DAC — once or twice weekly is easier than daily injections.
Stacked with ipamorelin: Modified GRF 1-29 is the community-standard pairing. Two-pathway synergy (GHRH + ghrelin receptor).
Deepest IGF-1 elevation: CJC-1295 with DAC produces largest sustained increase due to tonic stimulation.
Older adults with sarcopenia: Pulsatile dosing (Mod GRF + ipamorelin) is typical community preference.
Cancer history concerns: None may be appropriate — IGF-1 elevation epidemiologically associated with elevated cancer risk.
The ipamorelin pairing
Modified GRF 1-29 + ipamorelin is the most-discussed combination in peptide-research space. Ipamorelin is a selective ghrelin receptor agonist (GHSR-1a). Mod GRF acts on GHRH receptor. Co-administration produces synergistic GH release. Both have short half-lives, pair well in bedtime pulsatile protocols. The "CJC + Ipamorelin" name is misleading — modern protocols use Mod GRF 1-29, not CJC with DAC.
The honest evidence framing
None of these three has Phase 3 trial evidence for body-composition, anti-aging, or recovery outcomes. Phase 1 PK data establishes reliable GH/IGF-1 elevation. Translation to clinical outcomes is community-experience-grade. The choice is more about pharmacological preference (pulsatile vs. tonic) and practical considerations than evidence-based superiority.
Frequently asked questions
Is CJC-1295 with DAC stronger than Modified GRF 1-29?
Same active peptide; different pharmacokinetics. CJC with DAC produces higher sustained IGF-1; Mod GRF produces discrete pulses.
Why is the CJC + Ipamorelin stack so popular?
Synergistic GH release through two different receptor pathways. Both have short half-lives that pair well in bedtime protocols.
Can I get these prescribed?
Sermorelin via compounding is more accessible than CJC-1295 or Mod GRF (research-grade only). Compounding access has tightened with 2023 FDA actions.
Do these work as well as exogenous GH?
No, in terms of magnitude. The argument for GHRH analogs is preserved feedback regulation rather than maximum magnitude.
Are these safe long-term?
Less is known than for FDA-approved GH analogs. Sustained IGF-1 elevation carries theoretical cancer-risk considerations.
References
- Teichman SL, et al. Prolonged stimulation of GH and IGF-I secretion by CJC-1295. J Clin Endocrinol Metab. 2006;91(3):799-805. https://pubmed.ncbi.nlm.nih.gov/16352683/
- Sigalos JT, Pastuszak AW. The safety and efficacy of growth hormone secretagogues. Sex Med Rev. 2018;6(1):45-53. https://pubmed.ncbi.nlm.nih.gov/28526632/
We update articles as new trials publish and the evidence base evolves. Last reviewed: May 2026.