How Does IGF-1 Work? Mechanism of Action, Per the Research

What IGF-1 is, in mechanism terms

Insulin-like growth factor 1 (IGF-1) is a peptide hormone that circulates bound to carrier proteins and signals through a cell-surface receptor tyrosine kinase. A 2021 review of IGF-1 signalling in glucose metabolism described IGF-1 as structurally and functionally related to insulin, acting through the IGF-1 receptor (IGF-1R) and overlapping with insulin receptor signalling at several nodes (PMID 34208601). A 2021 review of the IGF-1 pathway in viral infections similarly summarised IGF-1R as the principal receptor initiating downstream phosphorylation cascades in many cell types (PMID 34452353).

This page summarises how the published literature describes that mechanism. It separates what reviews treat as established receptor-level pharmacology from downstream links that are still described as proposed, model-dependent or preclinical. For a broader orientation to the compound itself, see the IGF-1 overview.

Upstream: the growth hormone-IGF-1 axis

Most mechanistic reviews place IGF-1 downstream of growth hormone (GH). A 2020 review of classical and novel GH receptor signalling pathways reported that GH binding to its receptor activates JAK2 and STAT5B, with STAT5B driving transcription of target genes including IGF-1 (PMID 32835785). A 2012 review of growth hormone and cell growth described GH-stimulated IGF-1 production as a central route by which GH influences tissue growth, with additional direct GH receptor effects on cells (PMID 23182823).

The same JAK2-STAT5B module has been examined in bone biology: a 2013 review discussed the JAK2-STAT5B pathway in relation to osteoblast differentiation and the GH/IGF-1 axis in skeletal tissue (PMID 24470975). In mechanism terms, this means IGF-1 is both a hormone in its own right and a messenger that carries part of the GH signal to peripheral tissues, as described in those reviews (PMID 32835785).

Receptor targets: IGF-1R, insulin receptor and hybrids

Reviews consistently describe IGF-1R as a transmembrane receptor tyrosine kinase that autophosphorylates after ligand binding and recruits adaptor proteins such as insulin receptor substrate (IRS) family members and Shc (PMID 34452353). Because IGF-1R and the insulin receptor are closely related, the 2021 glucose-metabolism review reported cross-talk between the two systems, including shared substrates and overlapping effects on glucose uptake and metabolic reprogramming in colorectal cancer cells (PMID 34208601). A 2010 Science Signaling focus issue on metabolic signals framed insulin- and IGF-related signalling as part of a wider network linking nutrient status to cellular responses (PMID 21139135).

Ligand availability is not fixed. A 2018 review of protein restriction and cancer reported that dietary protein intake influences circulating IGF-1 levels and IGF-1 pathway activity, positioning nutrition upstream of receptor engagement (PMID 29596961).

Inside the cell: the two principal branches

PI3K-AKT-mTOR

The branch most often described as the anabolic and pro-survival arm runs from IRS proteins to PI3K, AKT and mTOR. The 2021 viral-infection review reported that IGF-1R activation of PI3K/AKT influences cell survival, protein synthesis and, in the contexts reviewed, host-virus interactions (PMID 34452353). A 2024 review of IGF-1 signalling in the heart described PI3K-AKT signalling as a core element of cardiac IGF-1 biology, with downstream consequences for cardiomyocyte growth and stress responses (PMID 38713091).

RAS-RAF-MEK-ERK (MAPK)

The second branch, recruited through Shc/Grb2, converges on ERK and is generally described in relation to proliferation and differentiation. The 2021 viral-infection review summarised both the PI3K/AKT and MAPK arms as downstream of IGF-1R engagement (PMID 34452353), and the 2021 glucose-metabolism review described how these cascades intersect with metabolic enzymes and glucose transport in tumour cells (PMID 34208601).

Downstream physiology described in the literature

Skeletal muscle

A 2021 review of pharmacologic approaches to prevent skeletal muscle atrophy after spinal cord injury discussed IGF-1-related signalling among the anabolic pathways considered in that setting, and described the evidence base as still developing (PMID 34461564). That review did not establish IGF-1 as a treatment; it summarised mechanistic rationale and the preclinical work behind it (PMID 34461564).

Bone and mechanical loading

A 2018 study of IGF-1 signalling in skeletal mechano-transduction reported that IGF-1 signalling contributed to how bone cells responded to mechanical loading, with effects described as cell-type specific in the models used (PMID 28980721). This work sits in the preclinical tier: it describes cellular mechanism rather than clinical outcomes (PMID 28980721). The related osteoblast-differentiation review added that JAK2-STAT5B signalling intersects with the GH/IGF-1 axis in bone-forming cells (PMID 24470975).

Heart

The 2024 cardiac review reported that IGF-1 signalling in the heart has both physiological and maladaptive faces depending on context, and highlighted newer insights into how receptor isoforms and signalling partners shape the response (PMID 38713091). The authors framed several of these distinctions as areas of active investigation rather than settled physiology (PMID 38713091).

Glucose handling and metabolism

Because IGF-1R shares substrates with the insulin receptor, reviews describe metabolic consequences alongside growth effects. The 2021 review reported that IGF-1 signalling influenced glucose metabolism in colorectal cancer cells, including pathways governing glucose uptake and utilisation (PMID 34208601). The 2010 focus issue placed such signalling within the broader set of metabolic signalling networks that link nutrient availability to cell behaviour (PMID 21139135).

Immune and antiviral contexts

The 2021 viral review reported that several viruses interact with the IGF-1 signalling pathway, and that pathway activity can influence infected-cell survival (PMID 34452353). A 2025 report in Scientific Reports described IGF-1 as a regulator of cancer cell immune evasion in prostate cancer models (PMID 41184420). Researchers presented that work as preclinical mechanism, not as a clinical finding (PMID 41184420).

Ageing and longevity pathways

A 2019 review of conserved signalling pathways genetically associated with longevity across species reported that insulin/IGF-1-like signalling is among the most repeatedly implicated pathways in model-organism lifespan genetics (PMID 31109448). The direction described in that literature is that reduced signalling through this axis associates with extended lifespan in several models, which is the opposite framing from anabolic applications (PMID 31109448).

Established mechanism versus proposed mechanism

How to read the evidence tiers

• Reviews of receptor biology. These synthesise decades of cell work; the 2021 viral-infection review and the 2021 glucose-metabolism review are examples of pathway-level syntheses rather than single experiments (PMID 34452353, PMID 34208601).
• Cell and tissue experiments. The 2018 mechano-transduction work reported cell-specific IGF-1 signalling responses in skeletal tissue models (PMID 28980721).
• Model-organism genetics. Lifespan associations with insulin/IGF-1-like signalling were drawn from cross-species genetic studies, not from human intervention trials (PMID 31109448).
• Disease-model mechanism. The 2025 prostate cancer report described immune-evasion signalling in experimental systems (PMID 41184420).

Mechanism-linked signals: What Studies Report

Mechanism papers also describe why the same pathway attracts caution. Researchers reported that IGF-1 signalling supported glucose metabolism and growth programmes in colorectal cancer cells (PMID 34208601), and a 2025 study reported that IGF-1 regulated immune evasion in prostate cancer models (PMID 41184420). A 2018 review of protein restriction and cancer discussed lowering IGF-1 pathway activity as a mechanistic rationale in oncology research (PMID 29596961). In the heart, the 2024 review reported that IGF-1 signalling can be adaptive or maladaptive depending on context (PMID 38713091). None of these papers reported dosing information for human use, and this page therefore states none.

Limits of the mechanism literature

Three limits recur. First, pathway maps are generalised from multiple cell types, and the 2018 bone work reported that responses were cell-specific rather than uniform (PMID 28980721). Second, much of the detailed signalling evidence is preclinical, as in the 2025 prostate cancer report (PMID 41184420). Third, the axis is bidirectional in its implications: the same signalling that reviews associate with growth and survival is the signalling whose reduction is associated with longevity in model organisms (PMID 31109448). Mechanistic plausibility is not the same as demonstrated clinical benefit, a distinction the muscle-atrophy review made explicit when describing candidate pharmacologic approaches (PMID 34461564).

This page is for educational purposes only and is not medical advice; consult a licensed physician about any medical question, medication or hormone-related condition.

References

• Insulin-Like Growth Factor 1 (IGF-1) Signaling in Glucose Metabolism in Colorectal Cancer (International Journal of Molecular Sciences, 2021)
• Protein restriction and cancer (Biochimica et Biophysica Acta. Reviews on Cancer, 2018)
• IGF-1 signaling mediated cell-specific skeletal mechano-transduction (Journal of Orthopaedic Research, 2018)
• The IGF-1 Signaling Pathway in Viral Infections (Viruses, 2021)
• Focus issue: metabolic signals (Science Signaling, 2010)
• Classical and novel GH receptor signaling pathways (Molecular and Cellular Endocrinology, 2020)
• IGF-1 regulates cancer cell immune evasion in prostate cancer (Scientific Reports, 2025)
• Growth hormone and cell growth (Endocrine Development, 2012)
• Conserved signaling pathways genetically associated with longevity across the species (Biochimica et Biophysica Acta. Molecular Basis of Disease, 2019)
• Pharmacologic approaches to prevent skeletal muscle atrophy after spinal cord injury (Current Opinion in Pharmacology, 2021)
• New Insights into IGF-1 Signaling in the Heart (Physiology, 2024)
• JAK2-STAT5B pathway and osteoblast differentiation (JAK-STAT, 2013)