IGF-1 LR3 vs MK-677 (Ibutamoren)
A detailed comparison to help you understand the differences and choose the right peptide for your research goals.
IGF-1 LR3
IGF-1 LR3 (Long R3 Insulin-like Growth Factor-1) is a modified version of IGF-1 with extended half-life and enhanced potency. The modifications prevent binding to IGF binding proteins, increasing bioavailability.
Full details →MK-677 (Ibutamoren)
MK-677, also known as Ibutamoren, is an orally active growth hormone secretagogue. Unlike peptides, it can be taken orally and has a long half-life, providing 24-hour GH elevation.
Full details →Side-by-Side Comparison
| Aspect | IGF-1 LR3 | MK-677 (Ibutamoren) |
|---|---|---|
| Dose Range | 20 mcg–100 mcg | 10 mg–25 mg |
| Frequency | 1x daily | 1x daily |
| Cycle Length | 4–6 weeks | 8–24 weeks |
| Route | subcutaneous | oral |
| Mechanism | Binds to IGF-1 receptors to promote protein synthesis, muscle growth, and fat metabolism. The LR3 modification (13 amino acid extension and arginine substitution) extends half-life from minutes to 20-30 hours. | Acts as a potent, selective agonist of the ghrelin receptor (GHS-R1a). Increases GH and IGF-1 levels without affecting cortisol. Mimics ghrelin's GH-releasing effects. |
| Typical Dosage | Research protocols typically use 20-100mcg daily, often divided into multiple injections or administered bilaterally to target muscles. | Typical dosing: 10-25mg taken orally once daily. Often taken at night due to sleep benefits and appetite increase. |
| Administration | Intramuscular injection (site-specific growth) or subcutaneous for systemic effects. Often cycled 4-6 weeks on, equal time off. | Oral administration (capsule or liquid). Can be taken with or without food. Long half-life allows once-daily dosing. |
| Side Effects | Hypoglycemia, joint pain, water retention, potential jaw/hand growth with extended use, and injection site reactions. | Increased appetite and water retention are most common. May cause lethargy, vivid dreams, and mild numbness. Can affect blood glucose and insulin sensitivity. |
| Best For |
What They Have in Common
IGF-1 LR3, MK-677 (Ibutamoren) are both commonly used for:
Key Differences
Unique to MK-677 (Ibutamoren):
Which Has Stronger Evidence?
| Goal | IGF-1 LR3 | MK-677 (Ibutamoren) |
|---|---|---|
| Muscle Growth | high | high |
| Fat Loss | medium | medium |
| Recovery & Healing | medium | medium |
Key Studies
IGF-1 LR3
- IGF-1 LR3 does not promote growth in late-gestation growth-restricted fetal sheep.
American journal of physiology. Endocrinology and metabolism, 2025
- Revolutionary decellularized Alstroemeria stem-based nerve conduit integrated with GelMA and controlled IGF-1 LR3 release for enhanced rat sciatic nerve regeneration.
International journal of biological macromolecules, 2025
- Attenuated glucose-stimulated insulin secretion during an acute IGF-1 LR3 infusion into fetal sheep does not persist in isolated islets.
Journal of developmental origins of health and disease, 2023
MK-677 (Ibutamoren)
- Knowing the minimal detectable dose can facilitate the interpretation of a hair test result: II. Case example with ibutamoren (MK-677), a growth hormone secretagogue.
Clinica chimica acta; international journal of clinical chemistry, 2026
- Hepatotoxicity induced by MK-677.
BMJ case reports, 2025
- Investigating the P53-dependent anti-cancer effect of ibutamoren in human cancer cell lines.
Basic & clinical pharmacology & toxicology, 2025
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