IGF-1

Definition

Insulin-like Growth Factor 1 (IGF-1) is a 70-amino-acid polypeptide hormone structurally similar to insulin. It is primarily produced in the liver in response to growth hormone (GH) stimulation and acts as the principal mediator of GH’s anabolic effects throughout the body.

Role in the GH-IGF-1 Axis

IGF-1 is the downstream effector of the growth hormone signalling cascade. When GH binds its receptor on hepatocytes, it triggers JAK2-STAT5 signalling that upregulates IGF-1 gene transcription. Circulating IGF-1 then acts on target tissues to promote protein synthesis, cell proliferation, and differentiation. This axis is central to growth, development, and tissue maintenance.

IGF-1 circulates bound to IGF-binding proteins (IGFBPs), primarily IGFBP-3 and the acid-labile subunit (ALS), which regulate its half-life and tissue availability. Free IGF-1 represents a small but biologically active fraction.

Relevance to Peptide Research

Many peptides studied in research contexts — including CJC-1295, Ipamorelin, Sermorelin, and MK-677 — exert their effects partly through elevating IGF-1 levels. Measuring serum IGF-1 is a common biomarker in GH-related peptide studies. Variants like IGF-1 LR3 and DES(1-3) IGF-1 are modified forms with altered binding protein affinity and potency, frequently encountered in preclinical research.

Related Peptides

Peptide profiles that reference “IGF-1” in their research content.