IGF-1 LR3 in Canada: A Research Guide to the Long-Acting Insulin-Like Growth Factor Analogue

Why IGF-1 LR3 deserves its own growth-hormone guide#

IGF-1 LR3 Canada searches often come from researchers who have already explored the growth-hormone secretagogue archive and are looking for the next mechanistic layer. Northern Compound has dedicated guides for CJC-1295 with DAC, Ipamorelin, MK-677, Sermorelin, Tesamorelin, and every major GHRP-family compound. What was missing was a guide that addresses the mediator rather than the stimulus. Every secretagogue in that list converges on a single downstream output: insulin-like growth factor 1. A researcher who understands GH pulsatility but has never examined IGF-1 receptor biology is missing the effector half of the axis.

That gap matters because IGF-1 LR3 is not simply a "stronger version" of GH stimulation. It is a completely different class of research tool. GH secretagogues act on the hypothalamus and pituitary to increase endogenous GH pulses, which in turn stimulate hepatic IGF-1 synthesis and paracrine IGF-1 release from target tissues. IGF-1 LR3 bypasses the entire neuroendocrine loop and acts directly on the IGF-1 receptor in peripheral tissues. The pharmacological independence is profound: a protocol using CJC-1295 without DAC and Ipamorelin is studying hypothalamic-pituitary regulation, pulsatile GH secretion, and feedback dynamics. A protocol using IGF-1 LR3 is studying receptor-mediated anabolic signalling, tissue-level IGF-1R phosphorylation, and PI3K/AKT pathway activation. The two protocols answer different questions, and conflating them produces interpretive noise.

This guide treats IGF-1 LR3 as research-use-only material. It does not provide dosing instructions, route guidance for human use, body-composition recommendations, anti-ageing protocols, or medical advice. The useful question is narrower: what is IGF-1 LR3, how does it differ from native IGF-1 and from GH secretagogues, what does the evidence actually say, and what should Canadian researchers verify before sourcing it?

What IGF-1 LR3 is at the molecular level#

IGF-1 LR3 is a recombinant analogue of human insulin-like growth factor 1. The native human IGF-1 molecule is a 70-amino-acid single-chain polypeptide with a molecular weight of approximately 7,649 Da. It shares structural homology with proinsulin, including A and B domains connected by a C-peptide region, and binds with high affinity to the IGF-1 receptor, with lower affinity to the insulin receptor and the IGF-2 receptor.

The "LR3" designation refers to two specific modifications that distinguish the analogue from the native sequence:

1. An N-terminal extension of 13 amino acids. This extension is derived from the Escherichia coli peptide signal sequence used in recombinant expression systems. Its functional consequence is a substantial reduction in binding affinity to IGF-binding proteins (IGFBPs), particularly IGFBP-3, which normally sequesters the majority of circulating IGF-1 and limits its bioavailability.

2. A substitution of arginine for glutamic acid at position 3. The arginine at position 3 further reduces IGFBP binding while preserving IGF-1 receptor affinity. The combined effect of the extension and the substitution is that IGF-1 LR3 binds the IGF-1R with approximately 2% the affinity of native IGF-1 for IGFBPs, but retains full agonist activity at the IGF-1 receptor.

The resulting molecule is an 83-amino-acid protein with a molecular weight near 9,111 Da. For analytical verification, a credible IGF-1 LR3 product listing should provide:

1. Batch-specific HPLC purity with peak integration, method conditions, and lot number. Because the molecule is larger than typical synthetic peptides, reversed-phase chromatography may require different column chemistries and gradient conditions than those used for short peptides.
2. Mass-spectrometry identity confirmation showing the expected molecular ion consistent with the ~9.1 kDa mass. SDS-PAGE or native PAGE with Coomassie staining is often used as a complementary identity check for recombinant proteins.
3. Sequence confirmation where available, by peptide mapping, tandem MS, or N-terminal sequencing.
4. Declared host-cell protein and endotoxin limits. Because recombinant proteins are produced in bacterial or mammalian expression systems, residual host-cell proteins and endotoxin are relevant quality parameters that do not apply to chemically synthesized peptides.
5. Bioactivity assay where available, measuring IGF-1R phosphorylation or cell-proliferation response in a standardised assay such as the MCF-7 cell proliferation model.
6. Fill amount stating the actual protein content per vial, not just the total lyophilisate mass.
7. Storage and shipping guidance appropriate for a recombinant protein: typically lyophilised, protected from light, and stored at -20 °C or below.

Functionally, IGF-1 LR3 is an IGF-1 receptor agonist. It binds to the alpha-subunit of the IGF-1R on target cells, induces autophosphorylation of the beta-subunit tyrosine kinase domains, and activates downstream signalling cascades. Unlike GHRH analogues such as Sermorelin or CJC-1295 with DAC, which act upstream of GH release, IGF-1 LR3 acts at the peripheral receptor level. Unlike GHRPs such as Ipamorelin or MK-677, which stimulate the ghrelin receptor to increase pituitary GH output, IGF-1 LR3 does not interact with GHSR-1a at all. Its mechanism is receptor-tyrosine-kinase signalling, not G-protein-coupled receptor signalling.

Mechanism: IGF-1 receptor signalling and the PI3K/AKT axis#

The IGF-1 receptor is a heterotetrameric receptor tyrosine kinase composed of two extracellular alpha-subunits and two transmembrane beta-subunits. When IGF-1 LR3 binds the alpha-subunits, the beta-subunit tyrosine kinase domains autophosphorylate each other on specific tyrosine residues, creating docking sites for adaptor proteins.

The two major downstream signalling pathways are:

PI3K/AKT/mTOR pathway#

Phosphoinositide 3-kinase (PI3K) is recruited to the phosphorylated receptor and generates phosphatidylinositol (3,4,5)-trisphosphate (PIP3) at the plasma membrane. PIP3 recruits phosphoinositide-dependent kinase 1 (PDK1) and AKT (protein kinase B) to the membrane, where AKT is phosphorylated and activated. Active AKT phosphorylates a wide range of substrates that promote cell survival, protein synthesis, and metabolic activity.

A key downstream target of AKT is the mammalian target of rapamycin (mTOR), specifically mTOR complex 1 (mTORC1). mTORC1 activation increases protein synthesis through phosphorylation of S6 kinase and 4E-BP1, promotes ribosomal biogenesis, and enhances cellular energy metabolism. In muscle-cell models, this pathway is the primary mechanistic explanation for IGF-1-driven myotube hypertrophy and myoblast proliferation.

AKT also phosphorylates and inactivates pro-apoptotic proteins such as BAD and caspase-9, and promotes nuclear exclusion of the forkhead box O (FOXO) transcription factors. The anti-apoptotic and survival-promoting effects of IGF-1 signalling are well documented in cell-culture models of serum deprivation, oxidative stress, and cytotoxic insult.

MAPK/ERK pathway#

The mitogen-activated protein kinase (MAPK) cascade is activated through the adaptor protein Grb2 and the guanine nucleotide exchange factor SOS, which activate Ras and subsequently Raf, MEK, and extracellular signal-regulated kinase (ERK). The MAPK/ERK pathway is more closely associated with cell proliferation, differentiation, and gene transcription than with acute metabolic regulation.

In myoblast models, IGF-1 stimulation activates both PI3K/AKT and MAPK/ERK, but the relative contributions differ by cell type, differentiation state, and culture conditions. Myoblast proliferation appears more dependent on MAPK/ERK signalling, while myotube hypertrophy and protein synthesis appear more dependent on PI3K/AKT/mTOR. A well-designed study should measure both pathways rather than assuming a single dominant mechanism.

Insulin receptor cross-talk#

IGF-1 LR3 binds the insulin receptor with approximately 1–2% the affinity of insulin. At high concentrations, this cross-reactivity can produce insulin-like metabolic effects, including increased glucose uptake through GLUT4 translocation. For researchers studying IGF-1R-specific biology, the insulin-receptor cross-talk is a confounder that should be measured or controlled. For researchers studying metabolic signalling more broadly, the cross-reactivity may be part of the biological signal rather than an experimental artefact.

IGF-1 LR3 versus native IGF-1: what the modifications change#

The structural differences between IGF-1 LR3 and native IGF-1 are not cosmetic. They fundamentally alter the molecule's pharmacokinetics, bioavailability, and experimental behaviour.

IGF-binding protein interactions#

In human serum, approximately 75–80% of circulating IGF-1 is bound to IGFBP-3 in a ternary complex that also includes the acid-labile subunit (ALS). This complex serves as a circulating reservoir that prolongs IGF-1 half-life but restricts tissue access. Only a small fraction of circulating IGF-1 is free and bioavailable.

IGF-1 LR3's reduced affinity for IGFBPs means that a larger proportion of the administered molecule remains free and accessible to tissue receptors. In research models, this translates into more potent effects at equivalent molar doses, not because the analogue is intrinsically more active at the receptor, but because more of it reaches the receptor before being sequestered.

Half-life and stability#

Native IGF-1 has a circulating half-life of approximately 12–15 hours in humans, primarily because of IGFBP binding and renal clearance. IGF-1 LR3 has a substantially longer effective half-life in animal models, measured in days rather than hours, because IGFBP sequestration and rapid clearance are reduced. The exact half-life depends on species, route, and assay methodology, but the directional difference is consistent across studies.

For research protocols, the longer half-life means that IGF-1 LR3 produces sustained receptor activation rather than pulsatile exposure. This pharmacokinetic profile is different from the episodic GH pulses that drive endogenous IGF-1 production, and it may produce different downstream transcriptional and metabolic responses.

Bioassay potency#

In standard cell-proliferation assays, IGF-1 LR3 is typically 2–3 times more potent than native IGF-1 on a molar basis. This increased potency is a pharmacokinetic artefact of improved bioavailability rather than a difference in intrinsic receptor affinity. In cell-culture models where IGFBPs are absent or negligible, the potency difference between IGF-1 LR3 and native IGF-1 is smaller.

The practical implication is that researchers comparing IGF-1 LR3 with native IGF-1 should normalise for free ligand concentration rather than total dose, and should account for IGFBP content in the experimental system.

IGF-1 LR3 versus GH secretagogues: downstream versus upstream#

The most important conceptual distinction for Canadian researchers is that IGF-1 LR3 and GH secretagogues occupy opposite ends of the same axis. A secretagogue such as CJC-1295 with DAC or Ipamorelin acts on the hypothalamus and pituitary to increase GH release. GH travels to the liver and other tissues, where it stimulates IGF-1 synthesis and secretion. The IGF-1 then acts on peripheral receptors to produce tissue effects. This is a neuroendocrine cascade with multiple feedback loops, pulsatile dynamics, and tissue-specific regulation.

IGF-1 LR3 bypasses the entire cascade. It does not stimulate the pituitary, does not increase serum GH, and does not depend on hepatic IGF-1 synthesis. It acts directly on the IGF-1 receptor in muscle, fat, bone, skin, and other tissues.

A comparison table clarifies the distinction:

The better research question is not "Which is stronger?" but "Which tool answers the mechanistic question?" If the hypothesis concerns hypothalamic-pituitary regulation, GH pulsatility, or feedback physiology, a secretagogue is the appropriate tool. If the hypothesis concerns IGF-1 receptor signalling, tissue-level anabolic responses, or PI3K/AKT pathway biology, IGF-1 LR3 is the appropriate tool.

Evidence map: muscle, metabolic, and tissue literatures#

A responsible IGF-1 LR3 review separates the evidence into at least three distinct literatures.

1. Muscle-cell and myoblast biology#

The muscle literature is the largest and most directly relevant. In vitro studies using C2C12 myoblasts, L6 myotubes, and primary human muscle cells have consistently shown that IGF-1 stimulates proliferation, differentiation, and hypertrophy through IGF-1R/PI3K/AKT/mTOR signalling. IGF-1 LR3 produces these effects at lower concentrations than native IGF-1 because of its improved bioavailability, but the qualitative response is the same: increased myogenin and MyoD expression, enhanced protein synthesis, and reduced proteolysis.

In rodent models, local overexpression of IGF-1 through gene therapy or direct muscle injection has been shown to increase muscle mass, fibre cross-sectional area, and force production. The well-known study by Barton-Davis et al. (1998) demonstrated that IGF-1 expression in mouse skeletal muscle produced significant hypertrophy, particularly in fast-twitch fibres, without the need for exercise or loading. These findings established IGF-1 as a central mediator of muscle growth signalling, though they do not prove that exogenous IGF-1 LR3 produces equivalent effects in human muscle in vivo.

2. Adipose tissue and metabolic regulation#

IGF-1 signalling also influences adipocyte biology. In preadipocyte models, IGF-1 promotes differentiation and lipid accumulation through PI3K/AKT-dependent pathways. In mature adipocytes, IGF-1 can increase glucose uptake and lipogenesis. These metabolic effects are complicated by insulin-receptor cross-talk: at high concentrations, IGF-1 LR3 can activate insulin-receptor signalling, producing insulin-like metabolic responses that are not specific to IGF-1R.

For metabolic researchers, the important design consideration is receptor specificity. If the goal is to study IGF-1R-specific adipose biology, insulin-receptor antagonists or IGF-1R-specific antibodies may be needed to isolate the signal. If the goal is to study integrated metabolic signalling, the cross-talk may be part of the biological response rather than a confounder.

3. Fibroblast, keratinocyte, and connective-tissue models#

IGF-1 is a well-established mitogen for fibroblasts and keratinocytes in cell culture. It stimulates collagen synthesis, extracellular matrix production, and wound-edge cell migration in in vitro wound-healing models. IGF-1 LR3 has been examined in dermal fibroblast cultures for its effects on collagen type I and III expression, hyaluronic acid synthesis, and matrix metalloproteinase regulation.

These connective-tissue literatures are mechanistically interesting but should not be translated into therapeutic claims for skin rejuvenation, wound healing, or cosmetic use. Cell-culture collagen production does not equate to clinical wound closure, and mitogenic stimulation of fibroblasts is not automatically beneficial in every tissue context.

Preclinical models: what they show and where they stop#

The preclinical literature for IGF-1 LR3 is substantial in volume but limited in clinical translation. Most published work uses cell-culture models or rodent studies with local administration. Systemic human pharmacology data for IGF-1 LR3 specifically are sparse, because the compound has not advanced through large-scale clinical trials as a therapeutic agent.

Muscle hypertrophy models#

In the classic Barton-Davis study, IGF-1 was overexpressed in mouse muscle using a viral vector, producing 15% increases in muscle mass and 20% increases in force production. The hypertrophy was fibre-type specific, with greater effects in fast-twitch than slow-twitch fibres. Subsequent work extended these observations to models of muscle injury, denervation, and age-related sarcopenia, generally showing that IGF-1 overexpression attenuates muscle loss and accelerates regeneration.

These findings are scientifically robust within their models. They do not establish that research-grade IGF-1 LR3 administered systemically to humans produces equivalent muscle growth. Viral overexpression produces sustained, high local concentrations that are pharmacologically different from intermittent bolus administration. Mouse muscle biology differs from human muscle in fibre-type distribution, regeneration capacity, and IGF-1 responsiveness. And research material is not formulated, dosed, or regulated as a therapeutic product.

Age-related decline models#

IGF-1 levels decline with age in humans and animals, and this decline has been correlated with reduced muscle mass, bone density, and metabolic rate. Some researchers have proposed that restoring IGF-1 signalling could attenuate age-related tissue loss. In rodent studies, IGF-1 administration or overexpression in aged animals has been reported to improve muscle mass, bone density, and cognitive performance in specific models.

However, the relationship between IGF-1 and longevity is more complex than a simple decline-and-replacement story. Genetic studies in model organisms have shown that reduced IGF-1/insulin signalling can extend lifespan, while increased signalling can promote growth and reproduction at the cost of longevity. The optimal IGF-1 level appears to be context-dependent, varying by tissue, age, metabolic state, and genetic background. A researcher who assumes that "more IGF-1 is better" is oversimplifying a nuanced biological system.

Safety and mitogenic cautions#

The most important preclinical caution is mitogenicity. IGF-1 is a potent cell-survival and proliferation signal. In normal physiology, this signal is tightly regulated by GH pulsatility, IGFBP sequestration, and feedback inhibition. Sustained, unregulated IGF-1 receptor activation can theoretically promote unwanted cell proliferation in tissues where growth signalling is already dysregulated.

This concern is theoretical rather than proven for research-grade IGF-1 LR3 in standard laboratory doses, but it is not trivial. Researchers should design protocols with appropriate controls, monitor for unexpected cell proliferation or transformation markers, and maintain clear research-use-only boundaries. A compound that activates major survival and growth pathways should not be treated as a benign nutritional supplement.

Canadian RUO context and compliance framing#

IGF-1 LR3 is not presented here as a Canadian treatment, wellness product, anti-ageing intervention, muscle-building agent, fat-loss compound, or hormone-replacement strategy. It is discussed as a research compound. Readers should not translate animal-model findings, cell-culture data, or supplier claims into personal-use decisions.

Canadian researchers should expect suppliers to label the product explicitly as research-use-only, avoid therapeutic claims, provide batch-specific analytical documentation, and ship with appropriate stability instructions. The compound is not a Health Canada-approved drug. It is not a natural health product. It is not a dietary supplement. It is a recombinant protein analogue with a specific research literature that does not currently include approved therapeutic indications in Canada.

The regulatory boundary is especially important for IGF-1 LR3 because the compound is frequently misrepresented in supplier marketing and online discussion. Claims about "clinical-grade IGF-1," "pharmaceutical purity," or "GMP manufacturing" should be treated with scepticism unless the supplier can provide documentation of actual GMP certification, drug establishment licence, or Health Canada approval. Research-grade material is manufactured and sold for laboratory use, not for human therapeutic administration.

Sourcing IGF-1 LR3: COA, purity, and analytical expectations#

Because IGF-1 LR3 is a recombinant protein rather than a chemically synthesised peptide, its analytical requirements are different from those of a 15-amino-acid synthetic peptide such as BPC-157 or TB-500. Canadian researchers should not apply the same COA checklist without adjustment.

Minimum documentation expectations#

1. HPLC or UPLC purity: A chromatogram showing the principal peak, integration percentage, method conditions, and lot number. For recombinant proteins, size-exclusion chromatography (SEC-HPLC) may be more informative than reversed-phase HPLC for detecting aggregates and degradation products.
2. Mass spectrometry: Electrospray ionisation (ESI-MS) or matrix-assisted laser desorption/ionisation (MALDI-TOF) confirming the expected molecular weight near 9.1 kDa. For larger proteins, SDS-PAGE with Coomassie staining and Western blotting using an anti-IGF-1 antibody are common complementary identity tests.
3. Peptide mapping or N-terminal sequencing: Confirmation that the N-terminal extension and the arginine-3 substitution are present as specified.
4. Bioactivity assay: A cell-based assay measuring IGF-1R phosphorylation or cell proliferation, with a reference standard comparison. This is particularly important for recombinant proteins because HPLC purity does not guarantee biological activity.
5. Endotoxin testing: LAL chromogenic or gel-clot assay with a stated limit, typically < 5 EU/g or lower for research-grade material.
6. Host-cell protein (HCP) assay: Where available, documentation of residual HCP levels from the expression system.
7. Sterility: Where claimed, method and acceptance criteria should be documented.
8. Fill amount and formulation: The vial should state the net protein content, not just the total lyophilised mass. Excipients such as mannitol or trehalose should be listed.
9. Storage and stability data: Guidance on reconstitution, shelf life, and recommended storage temperature before and after reconstitution.

Supplier red flags#

• A product labelled only "growth factor" or "IGF" without specifying LR3, native IGF-1, or the exact sequence.
• A COA that reports only total lyophilisate mass without net protein content or purity.
• Absence of mass spectrometry, SDS-PAGE, or bioactivity data.
• Claims about muscle gain, fat loss, anti-ageing, or performance enhancement on the product page.
• Pricing or packaging oriented toward consumer rather than laboratory use.
• Confusion with GH secretagogues such as CJC-1295, Ipamorelin, or MK-677.

Lynx Labs lists IGF-1 LR3 in the specialty category and is the domestic supplier Northern Compound currently points readers toward for Canadian research-source evaluation. That recommendation is based on the same criteria applied elsewhere: batch documentation, domestic fulfilment, product-category clarity, and attribution-transparent outbound links. Researchers should still verify the current lot's COA before using any material in an experiment.

Storage, solubility, and handling cautions#

IGF-1 LR3 is a recombinant protein, and its handling requirements reflect that identity. Lyophilised recombinant proteins are generally stable at -20 °C for months to years when protected from moisture and light. Reconstituted solutions are less stable and more vulnerable to aggregation, oxidation, and adsorption to container surfaces.

The molecule is basic and can be difficult to dissolve in neutral aqueous buffers. Some suppliers recommend reconstitution in a small volume of dilute acetic acid (0.1%) to improve solubility, followed by dilution into bacteriostatic water or the final assay buffer. The acidic step should be documented, and the final pH should be confirmed to be compatible with the experimental system. Northern Compound's reconstitution guide covers general handling principles, but researchers should follow supplier-specific guidance for this recombinant protein.

Aggregation is a particular concern for IGF-1 LR3. The molecule can form non-covalent aggregates during freeze-thaw cycles or after prolonged storage in solution. Visible turbidity, precipitation, or loss of bioactivity may indicate aggregation. Researchers should avoid repeated freeze-thaw, should aliquot reconstituted material into single-use portions, and should discard solutions that show visible particulates or precipitates.

Adsorption to glass and plastic surfaces is another practical issue. Dilute protein solutions can lose significant activity through surface binding, particularly in polystyrene containers. Pre-coating containers with a carrier protein such as bovine serum albumin (BSA) or using low-binding plastics can reduce this loss. The exact handling protocol depends on concentration, container material, and assay sensitivity.

Common misrepresentations and red flags#

IGF-1 LR3 is a useful test of whether a peptide article is doing science or advertising. Several true statements can be arranged into unsupported conclusions.

The first misrepresentation is the conflation of IGF-1 LR3 with GH secretagogues. Supplier pages sometimes describe IGF-1 LR3 as a "GH peptide" or place it in the same category as CJC-1295 and Ipamorelin. This is mechanistically wrong. IGF-1 LR3 does not stimulate GH release, does not act on the pituitary, and does not produce the same endocrine profile as a secretagogue. A researcher who buys IGF-1 LR3 expecting GH pulsatility data will be disappointed.

The second misrepresentation is potency inflation. Because IGF-1 LR3 is more potent than native IGF-1 in bioassays, some suppliers describe it as "super-IGF-1" or imply that it is a fundamentally stronger molecule. The increased potency is a bioavailability effect, not a receptor super-agonism effect. In IGFBP-free cell culture, the two molecules are much closer in potency.

The third misrepresentation is therapeutic leapfrogging. The muscle-hypertrophy literature in rodents is compelling, but it does not justify claims that research-grade IGF-1 LR3 is appropriate for human muscle-building, athletic performance, or body-composition manipulation. Viral overexpression in mice is not equivalent to bolus injection in humans.

The fourth misrepresentation is the "clinical-grade" label. There is no approved clinical indication for IGF-1 LR3 in Canada, the United States, or the European Union. Native recombinant human IGF-1 (mecasermin) is approved for specific growth disorders, but mecasermin is not IGF-1 LR3, and the approved indication does not transfer to the analogue.

The fifth misrepresentation is COA laundering. A supplier may have strong documentation for one product and weak documentation for another. A good BPC-157 COA does not validate IGF-1 LR3. Each recombinant protein lot needs its own identity, purity, bioactivity, and endotoxin verification.

How this guide fits the Northern Compound archive#

The growth-hormone archive is strongest when each article does a different job. The pillar guide maps the whole category. The CJC-1295 articles explain GHRH-analogue pharmacology. The Ipamorelin article explains selective ghrelin-receptor framing. The MK-677 article explains oral non-peptide secretagogue delivery. The GHRP articles explain the first- and second-generation GHRP lineage. What was missing was the article that explains the downstream mediator: the molecule that actually carries the anabolic signal from the liver and local tissues to the peripheral receptors.

That editorial role matters for search intent. A reader searching "IGF-1 LR3 Canada" may already understand GH secretagogues and want to know what the next tool in the axis does. The responsible answer is not a pushy buying page. It is a decision framework: understand the receptor, separate the evidence layers, distinguish it from secretagogues and native IGF-1, reject unsupported claims, and verify the source.

For that reason, this guide links to relevant Lynx product pages with attribution while keeping the article itself independent in tone. Readers can inspect IGF-1 LR3, CJC-1295 with DAC, Ipamorelin, and MK-677 listings, but the article's conclusion is not "buy the strongest one." The conclusion is that the right compound depends on receptor intent, endpoint design, confounder measurement, and supplier documentation.

That is the standard Northern Compound should apply across the archive: useful enough for commercial search traffic, cautious enough for research-use-only compliance, and specific enough that a serious reader learns something beyond the product name.

References and further reading#

• Barton-Davis E.R. et al. "Viral mediated expression of insulin-like growth factor I blocks the aging-related loss of skeletal muscle function." Proceedings of the National Academy of Sciences (1998). PubMed.
• Clemmons D.R. "Role of IGF-binding proteins in regulating IGF responses to changes in metabolism." Journal of Molecular Endocrinology (2018). DOI.
• Yakar S. et al. "Circulating levels of IGF-1 directly regulate bone growth and density." Journal of Clinical Investigation (2002). PubMed.
• Sandhu M.S. et al. "Circulating concentrations of insulin-like growth factor-I and development of glucose intolerance: a prospective observational study." The Lancet (2002). PubMed.
• Pollak M.N. et al. "Insulin-like growth factors and neoplasia." Nature Reviews Cancer (2004). PubMed.
• Frystyk J. "Free insulin-like growth factors — measurements and relationships to clinical endpoints." Growth Hormone & IGF Research (2004). DOI.
• LeRoith D. et al. "The somatomedin hypothesis: 2001." Endocrine Reviews (2001). PubMed.
• Kopchick J.J. et al. "Growth hormone receptor antagonists: discovery, development, and use in patients with acromegaly." Endocrine Reviews (2002). PubMed.
• Sesti G. et al. "Molecular mechanism of insulin resistance in type 2 diabetes mellitus: role of the insulin receptor, IRS proteins, and the PI3K/AKT pathway." Current Pharmaceutical Design (2007). DOI.