IGF-1 LR3 vs MK-677 (Ibutamoren): Mechanism, Specs & Reported Ranges Compared
Side-by-side comparison of IGF-1 LR3 and MK-677 (Ibutamoren) — receptor mechanism, half-life, vial sizes, reconstitution and reported study arms.
By PX1 Research Team · August 4, 2026
IGF-1 LR3 vs MK-677 (Ibutamoren) at a glance
| IGF-1 LR3 | MK-677 (Ibutamoren) | |
|---|---|---|
| Class | long R3 insulin-like growth factor-1 analog | orally active non-peptide ghrelin mimetic |
| Reported half-life | ~20–30 hours | ~24 hours |
| Vial sizes | 1 mg | 12.5 mg capsules |
| Typical reconstitution | 1 mg + 2 mL = 500 mcg/mL | oral capsule — no reconstitution |
| Research focus | IGF-receptor and myogenesis research | oral GH-secretagogue research |
Mechanistic difference
IGF-1 LR3 is an injectable growth-factor analog acting directly at the IGF receptor; MK-677 is an orally active ghrelin mimetic that raises endogenous GH and IGF-1 indirectly.
Reported study ranges side by side
IGF-1 LR3
| Study arm | Reported amount | Cadence |
|---|---|---|
| Low arm | 20 mcg | daily |
| Mid arm | 50 mcg | daily |
MK-677 (Ibutamoren)
| Study arm | Reported amount | Cadence |
|---|---|---|
| Low arm | 12.5 mg | daily |
| High arm | 25 mg | daily |
Practical handling differences
Both arrive lyophilized and shelf-stable. IGF-1 LR3 is typically prepared at 1 mg + 2 mL = 500 mcg/mL; MK-677 (Ibutamoren) at oral capsule — no reconstitution. Where half-lives differ, the literature's dosing cadence differs accordingly — longer-acting molecules are described weekly, shorter-acting ones daily or split.
Which one appears in which research context
IGF-1 LR3 shows up primarily in IGF-receptor and myogenesis research. MK-677 (Ibutamoren) is used in oral GH-secretagogue research. They are not interchangeable substitutes; the receptor profile, not the marketing category, determines where each is used.
Documentation and sourcing
Both are supplied at ≥99% HPLC purity with lot-level COAs at /coa. Product pages: IGF-1 LR3 · MK-677 (Ibutamoren).
How PX1 documents every lot
Every PX1 lot ships with HPLC purity, LC-MS identity, residual solvent, moisture (Karl Fischer), sterility and endotoxin data. Lot documentation is published at /purity-reports, /endotoxin-reports and /coa. Synthesis, purification, lyophilization and vial fill happen in U.S. facilities — see /manufacturing-process.
Research use only. PX1 Research supplies compounds for laboratory and in-vitro research. Nothing here is medical advice, a dosing recommendation, or an offer for human or veterinary use. Figures cited are reported from published laboratory literature.