IGF-1 LR3 for Muscle Growth: What the Evidence Shows
What human and animal studies show about IGF-1 LR3 for muscle growth, how strong that evidence is, and what is still unproven.
- Strongest evidence
- Animal
- Human studies
- 0
- PubMed records, our ledger
- Animal studies
- 6
- PubMed records, our ledger
- Studies we summarised
- 8
- with an outcome for muscle growth
Evidence for muscle growth
Each row is an outcome related to muscle growth from a published study, strongest design first. Animal and cell results are labelled and are not human results. User reports are not counted as evidence here.
| Outcome | Result | Study type | Source |
|---|---|---|---|
| Regulatory status and evidence for physique claims | The review notes no regulatory approval for physique- or performance-related indications of these peptides, including the long-acting IGF analogue. | Review | Frontiers in endocrinology 2026, PMID 42395176 |
| Fetal growth | One week of IGF-1 LR3 did not improve growth in growth-restricted fetal sheep. | Animal · sheep (not a human result)n = 14 | American journal of physiology. Endocrinology and metabolism 2025, PMID 39679943 |
| Body composition and cognition | Intranasal LR3-IGF-1 improved body composition (not specified in the abstract) in male 5XFAD mice but did not significantly change cognition. | Animal · mouse (not a human result) | Journal of Alzheimer's disease 2025, PMID 39610283 |
| Daily weight gain | In the second 9 days, LR3IGF-I-infused neonatal pigs gained 457 g/d versus 386 g/d for controls. | Animal · pig (not a human result) | The British journal of nutrition 2002, PMID 12067429 |
| Growth performance | A four-day infusion of 180 micrograms/kg/day LR3IGF-I decreased average daily gain, food intake and plasma IGFBP-3, IGF-I and insulin in pigs. | Animal · pig (not a human result) | The Journal of endocrinology 1997, PMID 9488001 |
| Overall growth | Fractional weights of adrenals, gut, kidneys and spleen increased with LR3IGF-I, but overall growth was not stimulated. | Animal · guinea pig (not a human result) | The Journal of endocrinology 1995, PMID 7561636 |
| Carcass protein | LR3-IGF-I had no positive effect on carcass protein accretion in tumour-bearing rats. | Animal · rat (not a human result) | The Biochemical journal 1994, PMID 8053901 |
| Growth in diabetic rats | The IGF-I variants were 2.5-3 times more potent than IGF-I at restoring growth in diabetic rats. | Animal · rat (not a human result) | The Biochemical journal 1993, PMID 7683875 |
| Muscle protein synthesis | All IGF peptides raised muscle protein-synthesis rates and RNA levels by up to 50%, IGF-I least. | Animal · rat (not a human result) | The Biochemical journal 1993, PMID 7683875 |
PubMed records for IGF-1 LR3 and muscle growth: 0 human, 6 animal (search counts, not studies we reviewed). Grades follow our evidence scale.
How strong is it?
Strongest evidence:Animal evidence, 2 of 4American journal of physiology. Endocrinology and metabolism 2025, PMID 39679943
A human randomized trial outweighs any number of animal studies. Animal and cell results show a mechanism worth testing, not that it works in people.
Other peptides people research for muscle growth
All peptides for muscle growth, comparedCommon questions
Does IGF-1 LR3 help with muscle growth?
The strongest study we summarise for muscle growth is animal evidence, across 8 studies with an outcome for muscle growth. That is not proof it works in people.
Is IGF-1 LR3 approved for muscle growth?
IGF-1 LR3 is Not FDA approved · research chemical. Which conditions that approval covers is set by the label; use for anything else is off-label.
What is the best peptide for muscle growth?
There is no single answer. Our muscle growth overview compares each candidate by evidence grade and legal status rather than by popularity.
More on IGF-1 LR3
DosageDoses used in published studies, with the source for each.CalculatorVial, water and dose to syringe units.Side effectsWhat labels and studies report, and what is unknown.ResultsStudy outcomes and when they were measured.PricePrice per mg and per week from dated listings. No vendor links.How to injectSites, syringe types and hygiene, step by step.
Sources
- 1The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration.Frontiers in endocrinology · 2026PMID 42395176Accessed 2 Oct 2026
- 2IGF-1 LR3 does not promote growth in late-gestation growth-restricted fetal sheep.American journal of physiology. Endocrinology and metabolism · 2025PMID 39679943Accessed 2 Oct 2026
- 3Intranasal long R3 insulin-like growth factor-1 treatment promotes amyloid plaque remodeling in cerebral cortex but fails to preserve cognitive function in male 5XFAD mice.Journal of Alzheimer's disease : JAD · 2025PMID 39610283Accessed 2 Oct 2026
- 4Insulin-like growth factor-I and analogues increase growth in artificially-reared neonatal pigs.The British journal of nutrition · 2002PMID 12067429Accessed 2 Oct 2026
- 5Long [R3] insulin-like growth factor-I reduces growth, plasma growth hormone, IGF binding protein-3 and endogenous IGF-I concentrations in pigs.The Journal of endocrinology · 1997PMID 9488001Accessed 2 Oct 2026
- 6Long R3 insulin-like growth factor-I (IGF-I) infusion stimulates organ growth but reduces plasma IGF-I, IGF-II and IGF binding protein concentrations in the guinea pig.The Journal of endocrinology · 1995PMID 7561636Accessed 2 Oct 2026
- 7Effects of insulin and insulin-like growth factors on protein and energy metabolism in tumour-bearing rats.The Biochemical journal · 1994PMID 8053901Accessed 2 Oct 2026
- 8Insulin-like growth factor-I and more potent variants restore growth of diabetic rats without inducing all characteristic insulin effects.The Biochemical journal · 1993PMID 7683875Accessed 2 Oct 2026
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