Ghrelin vs Mod-GRF(1-29)
A neutral, side-by-side comparison of two performance & growth hormone peptides — their mechanisms, dosing ranges, administration routes, side effects, and research evidence. For research and educational purposes only.
Ghrelin
Endogenous 28-amino acid peptide secreted primarily by the stomach that functions as both the primary hunger signal and a potent growth hormone secretagogue. The n-octanoyl modification at Ser-3 (acylated form) is required for GHS-R1a receptor binding and GH-stimulating activity. Understanding ghrelin explains the mechanism behind the entire GHRP class of research peptides.
Full profileMod-GRF(1-29)
Mod-GRF(1-29) is a stabilized analog of growth hormone-releasing hormone (GHRH) that spans residues 1–29 of the native peptide. Unlike CJC-1295 (which includes a Drug Affinity Complex for multi-day half-life), Mod-GRF(1-29) has a short ~30-minute active window — mimicking the natural GHRH pulse pattern. It is the preferred GHRH component for precise, pulsatile GH protocols when combined with a GHRP.
Full profile| Ghrelin | Mod-GRF(1-29) | |
|---|---|---|
| Category | Performance & Growth Hormone | Performance & Growth Hormone |
| Also known as | GHRL, growth hormone-releasing peptide endogenous, ghrelinergic peptide, acyl ghrelin | Modified GRF(1-29), CJC-1295 without DAC, Tetrasubstituted GRF, Sermorelin analog |
| Evidence | Investigational (in trials) | Research-stage |
| Dosing range | 0.5mcg/kg–2mcg/kg mcg/kg, IV or SC bolus; endogenous levels peak pre-meal | 100mcg–200mcg mcg, 2–3x daily, co-administered with a GHRP (pre-sleep, pre-workout, and/or upon waking) |
| Administration | Intravenous (research), Subcutaneous injection | Subcutaneous injection, Intramuscular injection |
| Key side effects | Appetite stimulation, Transient hyperglycemia, Water retention, GH pulse stimulation | Water retention (mild, dose-dependent), Tingling / numbness in extremities (carpal tunnel-like at high doses), Increased appetite (via GHRP component — less with Mod-GRF alone), Flushing or warmth at injection site |
| Cited sources | 2 references | 2 references |
Key differences
- Evidence level differs: Ghrelin is investigational (in trials), while Mod-GRF(1-29) is research-stage.
- Administration: Ghrelin — Intravenous (research), Subcutaneous injection; Mod-GRF(1-29) — Subcutaneous injection, Intramuscular injection.
- Dosing units differ: Ghrelin is dosed in mcg/kg, Mod-GRF(1-29) in mcg — they operate at different scales.
- Frequency: Ghrelin is typically IV or SC bolus; endogenous levels peak pre-meal; Mod-GRF(1-29) is 2–3x daily, co-administered with a GHRP (pre-sleep, pre-workout, and/or upon waking).
How each works
Ghrelin
Ghrelin was discovered in 1999 as the endogenous ligand for the GHS-R1a receptor. Its acylated form activates GH release from the pituitary, stimulates appetite via NPY/AgRP hypothalamic neurons, and modulates energy homeostasis and fat storage. The des-acyl form (majority of circulating ghrelin) lacks GHS-R1a activity but has independent cardiovascular and cellular effects.
Mod-GRF(1-29)
Native GHRH(1-29) is rapidly cleaved by plasma dipeptidyl peptidase IV (DPP-IV) within 2–3 minutes. Mod-GRF(1-29) incorporates four amino acid substitutions (positions 2, 8, 15, 27) that resist DPP-IV degradation, extending the half-life to approximately 30 minutes while preserving GHRH receptor binding affinity. This creates a half-life window aligned with physiological GH pulsatility, making it suitable for 2–3x daily injections that mimic natural GH release patterns.
This comparison aggregates public research and structured profile data for informational purposes only. It is not medical advice and does not recommend either compound for human use. Consult a qualified healthcare provider before considering any peptide.