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FDA Approved Growth Hormone Axis

IGF-1

also known as: Insulin-like Growth Factor 1, Somatomedin C, IGF-I

The effector molecule of growth hormone — the 70-amino-acid peptide that actually builds muscle, bone, and tissue when GH tells the liver to produce it.

A 70-amino-acid peptide structurally similar to insulin, produced primarily in the liver in response to GH, that mediates most of GH's anabolic effects via the IGF-1 receptor — available as FDA-approved mecasermin (Increlex) for primary IGF-1 deficiency.

Mechanism of action

Binds IGF-1R (receptor tyrosine kinase), triggering PI3K/Akt/mTOR (protein synthesis, cell survival) and RAS/MAPK (cell proliferation) pathways. In bone: chondrocyte and osteoblast stimulation. In muscle: myofibrillar protein synthesis and satellite cell activation. Circulating IGF-1 provides negative feedback to hypothalamic GH release.

Primary uses

  • Endogenous mediator of GH's growth-promoting effects
  • FDA-approved: mecasermin for Laron syndrome
  • Clinical biomarker: serum IGF-1 for GH therapy monitoring
  • Research: IGF-1R signaling in cancer and aging

Typical dosing

40-120 mcg/kg twice daily (with meals) (subcutaneous)

Mecasermin: 40 mcg/kg SC twice daily, titrated to 120 mcg/kg. Must be taken with meals (hypoglycemia risk). Black box warning.

Regulatory status

Recombinant IGF-1 (mecasermin/Increlex) is FDA-approved for severe primary IGF-1 deficiency (Laron syndrome). Not approved for athletic enhancement. Serum IGF-1 is the standard biomarker for monitoring GH therapy.

References

  1. [review] Laron Z. "Insulin-like growth factor 1 (IGF-1): a growth hormone." Mol Pathol. 2001;54(5):311-316.
  2. [pubmed] Chernausek SD, et al. "Long-term treatment with recombinant IGF-I in children with severe IGF-I deficiency." J Clin Endocrinol Metab. 2007;92(3):902-910.

Related peptides

IGF-1 LR3

A 13-amino-acid N-terminal extension plus Arg3 substitution gives IGF-1 LR3 roughly 2–3× the potency of native IGF-1 in bioassays — a research-reagent favorite that became a bodybuilding staple despite no human approval.

IGF-1 DES(1-3)

Deleting the first three amino acids of IGF-1 cripples IGFBP binding while preserving receptor activity — giving DES(1-3) roughly 10× the in vitro potency of native IGF-1 at promoting cell growth in IGFBP-rich environments.

Somatropin (HGH)

FDA-approved recombinant human growth hormone — the direct hormone replacement, with multiple clinical indications, prescription-only status, and specific federal criminal provisions against off-label distribution.

Mecasermin

Ipsen's recombinant human IGF-1 (Increlex) — FDA-approved in 2005 for severe primary IGF-1 deficiency; the direct replacement for IGF-1 in patients whose own IGF-1 production is inadequate despite normal GH levels.

MGF

The native, non-pegylated splice variant of IGF-1 produced by skeletal muscle in response to mechanical overload — extremely short-lived in vivo and therefore superseded by PEG-MGF in research-chemical markets.
Disclaimer

This entry is for educational purposes only and does not constitute medical advice. Dosing information reflects published regulatory or research data and is not a recommendation. Many compounds described here are not approved for human use in the United States. Consult a licensed medical professional before considering any peptide therapy.