IGF-1 LR3 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.
IGF-1 LR3
IGF-1 LR3 (Long Arg3 IGF-1) is a synthetic analogue of Insulin-like Growth Factor 1 with an amino acid substitution at position 3 and a 13-amino acid N-terminal extension. These modifications prevent binding to IGF-binding proteins (IGFBPs), dramatically extending its half-life from ~12 minutes (native IGF-1) to approximately 20–30 hours. IGF-1 LR3 is widely used in research for its ability to promote cellular growth, protein synthesis, hyperplasia, and nutrient uptake into muscle tissue.
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| IGF-1 LR3 | Mod-GRF(1-29) | |
|---|---|---|
| Category | Performance & Growth Hormone | Performance & Growth Hormone |
| Also known as | Insulin-like Growth Factor-1 Long R3, Long R3 IGF-1, Increlex (human equivalent) | Modified GRF(1-29), CJC-1295 without DAC, Tetrasubstituted GRF, Sermorelin analog |
| Evidence | Research-stage | Research-stage |
| Dosing range | 20mcg–100mcg mcg, Once daily post-workout, on training days only (common protocol) | 100mcg–200mcg mcg, 2–3x daily, co-administered with a GHRP (pre-sleep, pre-workout, and/or upon waking) |
| Administration | Subcutaneous injection, Intramuscular injection (into the trained muscle — site-specific protocols) | Subcutaneous injection, Intramuscular injection |
| Key side effects | Hypoglycemia (clinically significant — monitor blood sugar carefully), Jaw and organ growth with chronic high-dose use (theoretical at research doses), Fatigue and headaches, Joint pain | 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 | 3 references | 2 references |
Key differences
- Administration: IGF-1 LR3 — Subcutaneous injection, Intramuscular injection (into the trained muscle — site-specific protocols); Mod-GRF(1-29) — Subcutaneous injection, Intramuscular injection.
- Frequency: IGF-1 LR3 is typically Once daily post-workout, on training days only (common protocol); Mod-GRF(1-29) is 2–3x daily, co-administered with a GHRP (pre-sleep, pre-workout, and/or upon waking).
- Research depth: this profile cites 3 sources for IGF-1 LR3 vs 2 for Mod-GRF(1-29).
How each works
IGF-1 LR3
In vitro and animal research establishes IGF-1 LR3 as a potent anabolic and growth-promoting agent. It activates the IGF-1 receptor (IGF-1R) and downstream PI3K/Akt and MAPK/Erk pathways, promoting skeletal muscle hypertrophy and satellite cell activation. Its extended half-life makes it far more active systemically than native IGF-1. Research also documents its role in connective tissue repair, nerve regeneration, and fat oxidation. Human research is limited — most data comes from cancer cell biology and athletic performance settings.
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.