Insulin-Like Growth Factor 1 (IGF-1)
Also known as: Somatomedin C, IGF-I, Mechano-growth factor precursor
Overview
Insulin-Like Growth Factor 1 (IGF-1) is a 70-amino acid single-chain growth factor structurally homologous to insulin, primarily synthesized in the liver in response to growth hormone stimulation. IGF-1 mediates most of the anabolic effects of growth hormone including linear growth, muscle protein synthesis, and bone mineral accretion. Serum IGF-1 declines approximately 14% per decade after age 30, contributing to sarcopenia, reduced bone density, and metabolic changes associated with aging. Recombinant IGF-1 (mecasermin, Increlex) is FDA-approved for IGF-1 deficiency states.
Mechanism of Action
IGF-1 binds the IGF-1 receptor (IGF-1R), a receptor tyrosine kinase structurally homologous to the insulin receptor. IGF-1R autophosphorylation activates IRS-1/2 adapter proteins, leading to PI3K → PDK1 → Akt → mTORC1 signaling (protein synthesis, cell survival) and Ras → MEK → ERK1/2 signaling (cell proliferation). In skeletal muscle, Akt-mTORC1 activation phosphorylates p70S6K1 and 4E-BP1, driving ribosome biogenesis and mRNA translation for muscle protein synthesis. IGF-1 also inhibits FoxO-mediated expression of MuRF-1 and MAFbx (atrogenes), preventing muscle protein breakdown.
Potential Benefits
- Skeletal muscle protein synthesis stimulation
- Bone mineral density maintenance
- GH-mediated anabolic effects (mediator)
- Neuroprotection and neurite outgrowth promotion
- FDA-approved for primary IGF-1 deficiency (mecasermin)
Dosage Protocols
The following reflects doses used in published research studies. This is not medical advice. Consult a qualified healthcare professional.
| Beginner | 40 mcg/kg SC 2x daily |
| Intermediate | 80 mcg/kg SC 2x daily |
| Advanced | 120 mcg/kg SC 2x daily (max) |
| Cycle Duration | Chronic during growth years |
FDA-approved (Increlex) for pediatric severe primary IGF-1 deficiency. Adult use off-label/research. Research peptides (IGF-1 LR3, DES IGF-1) are distinct modified forms.
Use our Reconstitution Calculator to determine exact syringe units for your protocol.
Routes of Administration
Subcutaneous Injection ~100%
Inject just before or after a meal/snack to reduce hypoglycemia risk. Rotate sites.
Read our full Routes of Administration Guide for detailed comparison of all delivery methods.
Stacking Protocols
Popular research stacks involving Insulin-Like Growth Factor 1 (IGF-1):
Pediatric Growth Failure Protocol
Select cases of severe GH insensitivity (e.g., Laron syndrome) managed with IGF-1 replacement.
Research Muscle Stack (IGF-1 LR3)
Research combination layering IGF-1 LR3 with endogenous GH axis support (not FDA-approved, not Increlex).
Explore our complete Peptide Stacking Guide for more combinations and safety considerations.
Reconstitution
| Storage | Refrigerate 2-8°C. Do not freeze. Discard 30 days after first use. |
|---|
No reconstitution needed (pharmaceutical Increlex).
Need exact syringe measurements?
Amino Acid Sequence
Gly-Pro-Glu-Thr-Leu-Cys-Gly-Ala-Glu-Leu-Val-Asp-Ala-Leu-Gln-Phe-Val-Cys-Gly-Asp-Arg-Gly-Phe-Tyr-Phe-Asn-Lys-Pro-Thr-Gly-Tyr-Gly-Ser-Ser-Ser-Arg-Arg-Ala-Pro-Gln-Thr-Gly-Ile-Val-Asp-Glu-Cys-Cys-Phe-Arg-Ser-Cys-Asp-Leu-Arg-Arg-Leu-Glu-Met-Tyr-Cys-Ala-Pro-Leu-Lys-Pro-Ala-Lys-Ser-Ala
Side Effects & Safety
- Hypoglycemia (most important; insulin-like activity)
- Jaw pain and facial bone growth at high doses
- Edema
- Potential cancer risk with prolonged supraphysiological levels (controversial)
- Acromegaly-like features with chronic excess
Safety & Contraindications
This information is for educational purposes only. Consult a qualified healthcare provider before using any peptide.
Active Malignancy
Pregnancy / Lactation
Bleeding Disorders
Active Skin Infection at Injection Site
Pharmacokinetics
| Half-Life | ~5.8 hours (Increlex); ~12 min native free IGF-1 |
|---|---|
| Storage | Refrigerate at 2-8°C. Do not freeze. Protect from light. |
Synergistic Compounds
The following compounds have been studied alongside Insulin-Like Growth Factor 1 (IGF-1) for potential complementary or synergistic effects:
Learn More
References & Further Reading
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