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IGF-1 LR3

Performance & EnergyResearch-Grade

Last reviewed: September 26, 2026

Quick Facts

What it is
A long-acting engineered analog of insulin-like growth factor-1 (IGF-1) — structurally modified to resist deactivation and stay active far longer than the natural hormone, studied for muscle growth, hypertrophy, and recovery.
How it's taken
Subcutaneous (or intramuscular) injection, once daily — always with food
Half-life
~20–30 hours
Typical research dose
20–50 mcg per day, in 4–6 week cycles
Research status
Not FDA-approved — research use only. WADA-prohibited (Section S2).
On this page
  1. 1.Where to source IGF-1 LR3
  2. 2.What is IGF-1 LR3?
  3. 3.How does IGF-1 LR3 work?
  4. 4.What is IGF-1 LR3 used for?
  5. 5.How long does IGF-1 LR3 take to work?
  6. 6.How is IGF-1 LR3 dosed?
  7. 7.How is IGF-1 LR3 administered?
  8. 8.What does IGF-1 LR3 stack well with?
  9. 9.What are the side effects of IGF-1 LR3?
  10. 10.Does IGF-1 LR3 interact with other drugs?
  11. 11.How should IGF-1 LR3 be stored?
  12. 12.What are the limitations of IGF-1 LR3 research?
  13. 13.IGF-1 LR3 FAQ
  14. 14.References
  15. 15.Published Studies

Where to source IGF-1 LR3

IGF-1 LR3 is not FDA-approved for performance enhancement and is sold only as a research-grade peptide. Counterfeit and underdosed product is common in the gray market — verify Certificate of Analysis before purchase. The vendors highlighted below have been vetted for transparent third-party testing, traceable batch documentation, and verified discount codes.

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Ion Peptide15% off
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Vital Core Research20% off

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What is IGF-1 LR3?

IGF-1 LR3 is a synthetic 83-amino-acid analog of human insulin-like growth factor 1 (IGF-1) — also called Long Arg3 IGF-1, LR3-IGF-1, or Long R3 IGF-1. It contains two structural modifications: an arginine substitution at position 3 (“Arg3”) and a 13-amino-acid N-terminal extension (“Long”), producing a peptide with dramatically reduced binding to IGF binding proteins (IGFBPs) and a much longer half-life. A half-life of minutes for native IGF-1 and 20–30 hours for IGF-1 LR3 is commonly reported, though no published pharmacokinetic study or label has been identified establishing this figure for IGF-1 LR3. The extended bioavailability and ~3x greater potency than native IGF-1 make it one of the most-studied research peptides for muscle hypertrophy, recovery, and metabolic research. Often stacked with Follistatin or the GH Stack for compounded anabolic effect. New to peptide research? Start with the basics

Reported benefits:

  • Activates IGF-1 receptors directly, bypassing the GH/IGF-1 axis
  • Stimulates muscle protein synthesis via PI3K/Akt/mTOR pathway
  • Promotes hyperplasia (new muscle fiber formation) — rare among research compounds
  • Activates satellite cells for enhanced muscle repair and growth
  • Improves glucose and amino acid uptake into muscle tissue
  • 20–30 hour half-life enables once-daily dosing

Common research dose: Most research protocols use 20–50 mcg per day administered subcutaneously, often immediately post-workout. Cycles typically run 4–6 weeks followed by a 4-week off period. Doses above 50 mcg/day significantly increase hypoglycemia risk without proportional muscle-building benefit. Community-reported practice pairs each injection with food.

Where to buy: PP maintains a vetted list of peptide vendors with verified discount codes. See Verified Discount Codes for current options.

How does IGF-1 LR3 work?

IGF-1 LR3 binds directly to IGF-1 receptors on muscle cells, triggering two parallel growth cascades (PI3K/Akt/mTOR for protein synthesis and MAPK/ERK for cellular proliferation) while also activating satellite cells that enable both hypertrophy and hyperplasia. Its key advantage over native IGF-1 is structural: the Arg3 substitution and N-terminal extension prevent rapid deactivation by IGF binding proteins, extending half-life from minutes to 20–30 hours.

  1. IGF-1 Receptor Activation [1]. IGF-1 LR3 binds directly to IGF-1 receptors (IGF-1R) on muscle and other tissues with high affinity, initiating tyrosine kinase signaling. This is the same receptor activated by native IGF-1, but at sustained levels for 20–30 hours.
  2. PI3K/Akt/mTOR Pathway [2]. Receptor activation triggers the PI3K/Akt signaling cascade, which activates mTOR — the master regulator of protein synthesis. This increases translation of mRNA into muscle proteins, drives hypertrophy, and inhibits muscle protein breakdown.
  3. Reduced IGFBP Binding [3]. The Arg3 substitution and N-terminal extension drastically reduce IGF-1 LR3's affinity for IGF binding proteins (IGFBPs), particularly IGFBP-3. Native IGF-1 is rapidly bound by IGFBPs, which deactivate it within minutes. IGF-1 LR3 escapes this regulation, remaining bioactive in circulation up to 100 times longer.
  4. Satellite Cell Activation [4]. IGF-1 LR3 activates satellite cells (muscle stem cells responsible for repair and growth), enabling true hypertrophy through both increased fiber size and potentially new fiber formation (hyperplasia). Most muscle-building compounds drive hypertrophy only.
  5. MAPK/ERK Pathway [2]. Parallel to PI3K/Akt, IGF-1 LR3 activates the MAPK/ERK pathway, which drives cellular proliferation and differentiation. This is critical for the satellite cell activation and tissue regeneration effects.

What is IGF-1 LR3 used for?

IGF-1 LR3's research evidence base sits in skeletal muscle hypertrophy, post-injury muscle repair, bone density, and aging-related sarcopenia models. Most data is preclinical — no controlled human trials exist for IGF-1 LR3 specifically, though native IGF-1 has been extensively studied. The research areas below cover the published evidence base across muscle, bone, brain, and cardiac applications.

  1. Skeletal Muscle Hypertrophy [4][5]. Animal studies and preclinical research consistently show IGF-1 LR3 increases muscle protein synthesis, satellite cell proliferation, and muscle fiber growth. Effects are most pronounced when combined with mechanical loading (resistance training).
  2. Muscle Regeneration After Injury [4]. Direct injection of recombinant IGF-1 enhanced muscle healing in lacerated, contused, and strain-injured mouse muscle models, with measurable improvements at 2, 5, and 7 days post-injury. Effects on tetanic and fast-twitch strength were observed in human muscle strain studies.
  3. Bone Mineral Density [6]. IGF-1 stimulates bone formation via direct effects on osteoblasts. Higher serum IGF-1 levels correlate with greater bone mineral density in older subjects. Treatment with GH and IGF-1 increases BMD in adults.
  4. Cognitive and Neuroprotective Effects [7]. IGF-1 supports neuronal survival, synaptic plasticity, and neurogenesis. Limited research has explored IGF-1 LR3 specifically for cognitive applications, though native IGF-1 has neuroprotective effects in animal models.
  5. Sarcopenia and Aging Models [4]. IGF-1 LR3 is studied in aging muscle wasting models for its ability to support satellite cell function and reverse age-related declines in muscle protein synthesis.
  6. Cardiac Tissue [3]. Preclinical studies show IGF-1 LR3 stimulates fetal cardiomyocyte proliferation through both ERK and PI3K signaling pathways, suggesting potential cardiac repair applications.

How long does IGF-1 LR3 take to work?

IGF-1 LR3 effects develop progressively. Most users notice improved workout recovery within 3–5 days as muscle repair accelerates, then visible muscle fullness by week 2 (glycogen and water retention), and measurable strength gains by week 3 as the anabolic effects compound. Full hypertrophy effects are sometimes reported over a 4–6 week cycle when paired with consistent resistance training and adequate protein, though no trial or label has been identified establishing this timeframe.

Most users notice improved recovery from workouts within 3–5 days as muscle repair accelerates. Visible muscle fullness appears by week 2 due to increased glycogen and water retention. Measurable strength gains typically emerge by week 3 as the anabolic effects compound. Full hypertrophy effects develop over the 4–6 week cycle when paired with consistent resistance training and adequate protein intake. Without training stimulus, IGF-1 LR3's effects are minimal — the growth signal needs a mechanical-load context to drive meaningful adaptation.

How is IGF-1 LR3 dosed?

No trial — in any species — has established a muscle-hypertrophy or bodybuilding-relevant dose for IGF-1 LR3. The only dosing study of the analog identified administered it by continuous infusion to neonatal rats for an unrelated gastrointestinal endpoint. All the figures below for human subcutaneous use are community convention, not derived from any trial of the analog.

Prof. Peptide reports what trials established and what research communities practice, labelled separately. Neither is a recommendation.

Need to calculate a dose?

Use the Prof. Peptide dosage calculator for accurate reconstitution and dosing math.

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What the cited literature administered

Animal model, unrelated endpoint [8]. Steeb et al. (Pediatr Res, 1998, PMID 9803447) administered long [Arg3]IGF-I (IGF-1 LR3) to suckling Wistar rat pups by continuous subcutaneous infusion at 2–12.5 mcg per gram of body weight per day for about 6 days, to study intestinal enzyme maturation and gut growth — not muscle hypertrophy, and not a human-relevant dose basis. No adverse-event data beyond the study’s own growth endpoints is reported. No human trial of IGF-1 LR3 (as opposed to native IGF-1) has been identified at any dose, and no animal study of IGF-1 LR3 dosed for a muscle-hypertrophy endpoint has been identified either — the muscle-hypertrophy evidence cited elsewhere on this page [4] is native IGF-1 expressed endogenously in overloaded rat muscle, not IGF-1 LR3 administered exogenously.

Community-reported practice (unverified)

Reported research-community practice — not independently verified by Prof. Peptide, and not derived from the animal study above — is 20–30 mcg subcutaneously per day for a first cycle, rising to 30–50 mcg/day for established users, with roughly 40–50 mcg/day described as a practical ceiling above which extra dose is said to raise hypoglycemia risk without added benefit. This diverges from the cited animal study in species (human versus neonatal rat), route (a single daily bolus versus continuous infusion), dose basis (a flat mcg figure versus the study’s weight-based mcg/g/day), and population/endpoint (adult muscle-building versus neonatal intestinal growth) — no source was found deriving the community figures from that study’s own numbers. Cycles are commonly reported as 4–6 weeks on with a minimum 4 weeks off to allow IGF-1 receptor sensitivity to reset; some users report 5 days on/2 days off pulsing within a cycle to reduce receptor downregulation. These cycle-length and pulsing figures are likewise unverified community convention.

Training-day timing: inject within 30–60 minutes post-workout when muscles are primed for nutrient uptake and IGF-1 receptors are temporarily upregulated. Have a meal containing protein and carbohydrates ready within 30 minutes to prevent hypoglycemia and maximize anabolic effect. Rest-day timing: inject with morning meal. Reported practice avoids injecting fasted unless very experienced, citing IGF-1 LR3's potential for significant blood sugar drops.

The Prof. Peptide dosage calculator converts between milligram figures and syringe units for a given reconstitution; it performs the arithmetic and does not set a schedule.

How is IGF-1 LR3 administered?

IGF-1 LR3 is given as a subcutaneous injection — or intramuscular for site-specific effect — once daily during the cycle, using a small insulin syringe. The most emphasized point in community-reported practice is pairing injections with food: IGF-1 LR3's insulin-like glucose uptake effect can cause significant hypoglycemia if injected fasted. For the practical mechanics of insulin syringes, units vs mcg conversion, and subcutaneous technique, see the syringes and injection technique guide.

  1. Route. Subcutaneous injection, once daily during the cycle. Intramuscular is sometimes used for site-specific effect. Common SubQ sites: abdomen, thigh, upper arm.
  2. Time of day. Immediately post-workout on training days. Morning with food on rest days. Reported practice avoids fasted injections.
  3. Food required. Community-reported practice pairs each injection with a meal containing protein and carbohydrates within 30 minutes; skipping that reportedly causes hypoglycemia reliably.
  4. Site rotation. Rotating sites each day, with at least an inch between consecutive sites, is the convention for limiting localized irritation.
  5. Hypoglycemia prep. Keeping glucose tabs or simple sugar nearby for the first weeks of a cycle is a commonly reported precaution, since shakiness, sweating, or confusion are hypoglycemia symptoms that simple carbohydrates address.
  6. Missed dose. Reported practice skips and resumes the next day. The convention is not to double-dose — doubling significantly increases hypoglycemia risk.
  7. Cycle structure. 4–6 weeks on, 4+ weeks off. Continuous use risks receptor desensitization.

Timing context. IGF-1 LR3 is administered once daily via subcutaneous injection. The 20–30 hour half-life produces overlapping coverage at once-daily dosing — meal timing relative to injection matters far more than time of day. The two timing variables that matter most are food (pairing injection with protein + carbs within 30 minutes is reported to prevent hypoglycemia) and training (post-workout administration on training days takes advantage of upregulated receptor sensitivity in worked muscles).

AspectReported
FrequencyOnce daily; a 4–6 weeks on, 4+ weeks off cycle is reported community practice, not derived from a trial or label; Prof. Peptide has not independently verified it.
Best time of dayPost-workout on training days; morning with food on rest days. Fasted injection is reportedly avoided.
FoodRequired — inject with protein + carbs within 30 minutes to prevent hypoglycemia
Injection site rotationRotating between the abdomen, thigh, and upper arm without reusing the same site for the next injection is standard subcutaneous-injection practice — documented in FDA-approved injectable labels generally (e.g., Wegovy's and Mounjaro's own instructions to rotate with each dose), not specific to IGF-1 LR3.
Half-life~20–30 hours
Steady-stateReached within ~5–7 days at consistent once-daily dosing

Reconstitution math. Water volume sets concentration: a lower volume yields a higher concentration and a smaller syringe draw for a given mg amount, and the reverse for a higher volume. IGF-1 LR3 research vials are typically 1 mg. Because IGF-1 LR3 doses are small (20–50 mcg daily), 2 mL or 3 mL reconstitution is the common research convention — it gives larger, more precise unit draws at low dose. All units below are measured on a U-100 insulin syringe (100 units = 1 mL). The table assumes a 1 mg vial.

BAC waterConcentration20 mcg dose30 mcg dose40 mcg dose50 mcg dose
1 mL1 mg/mL2 units3 units4 units5 units
2 mL0.5 mg/mL4 units6 units8 units10 units
3 mL0.33 mg/mL6 units9 units12 units15 units

Units vs mcg. At a 1 mg vial, each unit drawn delivers 10 mcg of IGF-1 LR3 at 1 mL reconstitution, 5 mcg at 2 mL, and 3.3 mcg at 3 mL — the reconstitution volume determines the mcg-per-unit conversion. For very small doses (20–30 mcg), 2 mL or 3 mL reconstitution gives more precise syringe draws. For a primer on reading insulin syringes and choosing the right barrel size, see our guide on syringes and injection technique.

What does IGF-1 LR3 stack well with?

IGF-1 LR3 pairs naturally with compounds that drive complementary growth mechanisms (GH secretagogues for endogenous IGF-1 production, Follistatin for myostatin inhibition) and with recovery peptides during anabolic cycles. The most important pairing is non-peptide: resistance training and adequate protein. Without those, the growth signal has nothing to act on.

  1. Resistance training + 1.6–2.2 g/kg protein. Essential. IGF-1 LR3 amplifies the response to mechanical loading; without training stimulus and adequate protein, results are minimal.
  2. GH secretagogues. GH Stack (CJC-1295 + Ipamorelin) or MK-677 drive endogenous IGF-1 production while IGF-1 LR3 provides direct receptor activation. Reported protocols separate IGF-1 LR3 from GH peptides by at least 2–3 hours, citing receptor competition as the reason.
  3. Follistatin. Direct synergy. Follistatin removes the myostatin growth ceiling; IGF-1 LR3 drives the growth signal that pushes against it. Often paired in advanced muscle-building protocols.
  4. Recovery peptides during anabolic cycles. Wolverine Stack (BPC-157 + TB-500) accelerates tissue repair while IGF-1 LR3 drives hypertrophy — useful when heavier training loads put more strain on tendons and joints.
  5. MGF (Mechano Growth Factor). Sometimes combined for theoretical synergistic effects on muscle growth, though controlled research is limited.
  6. Conflicts: insulin or diabetes medications without supervision. IGF-1 LR3 has insulin-like effects on glucose uptake. Combining with insulin or sulfonylureas significantly increases hypoglycemia risk.

What are the side effects of IGF-1 LR3?

IGF-1 LR3's side-effect profile is dominated by hypoglycemia risk — its insulin-like effect on glucose uptake is the single most common adverse event, and it's avoidable by injecting with food. Less common moderate effects include joint pain, fluid retention, and carpal-tunnel-like numbness during cycles. The serious concerns are theoretical: accelerated growth in pre-existing tumors and receptor desensitization with sustained high-dose use. Most users mitigate by keeping doses at or below 50 mcg/day and cycling on/off.

Common (most users)

  1. Hypoglycemia. Most common side effect, especially if injected without food. Symptoms: shakiness, sweating, confusion, fatigue. Resolves with simple carbohydrates.
  2. Mild fatigue or sleepiness. Often appears in the 1–2 hours following injection.
  3. Injection site reactions. Mild redness or irritation, especially with daily dosing.

Less common (moderate)

  1. Joint pain or stiffness. Reported during cycles, often related to rapid strength gains outpacing connective tissue adaptation.
  2. Bloating or fluid retention. Inconsistent across users; typically resolves after cycling off.
  3. Numbness or tingling. Carpal-tunnel-like symptoms reported during higher-dose cycles, related to fluid retention.

Serious (rare)

  1. Severe hypoglycemia. Risk increases significantly above 50 mcg/day. Symptoms: shakiness, sweating, confusion, fainting. Always keep simple sugar available.
  2. Theoretical tumor-growth concern. IGF-1 LR3 drives cell proliferation through the MAPK/ERK pathway [2]; whether that could accelerate a pre-existing tumor is unresolved — no controlled human trial of the analog has measured cancer risk. On that mechanistic basis, a personal history of malignancy is treated as a theoretical exclusion in research contexts.
  3. Receptor desensitization. Sustained high-dose use can reduce future effectiveness — the basis for 4+ week off periods between cycles.

None of the following is established in a controlled human trial of the analog — they are precautionary exclusions applied in research contexts on mechanistic grounds. Because IGF-1 LR3 drives cell proliferation [2], a personal or family history of malignancy is treated as a theoretical exclusion; pregnancy and breastfeeding are avoided for lack of any safety data; the analog's insulin-like glucose-lowering effect makes uncontrolled diabetes a monitoring concern; and IGF-1's roles in blood-vessel and skeletal growth are why diabetic retinopathy and age under 21 (growth-plate closure) are commonly treated as exclusions. Always have food available when injecting, and keep glucose tabs or simple sugar nearby during the first weeks of a cycle.

Common question: What are the side effects of IGF-1 LR3?

Does IGF-1 LR3 interact with other drugs?

IGF-1 LR3's most important interaction is with blood-sugar-lowering medications — its insulin-like effect compounds hypoglycemia risk with insulin, sulfonylureas, and other diabetes drugs. Growth hormone competes for IGF-1 receptors when injected close together (space ≥2–3 hours apart). Combinations with anabolic-androgenic steroids are theoretically synergistic but unsupported by controlled data and increase overall side-effect risk.

  1. Insulin and diabetes medications. High risk of hypoglycemia. IGF-1 LR3 has insulin-like effects on glucose uptake. Diabetics should not use without medical supervision.
  2. Growth hormone (HGH). Competes for IGF-1 receptors when injected close together, with injections reported spaced at least 2–3 hours apart.
  3. Anabolic-androgenic steroids. Combination is theoretical synergy but increases overall side-effect risk. No controlled human data.
  4. Thyroid hormones. IGF-1 affects thyroid hormone metabolism; theoretical interaction in users on thyroid medication.

How should IGF-1 LR3 be stored?

  1. Lyophilized (powder) form: refrigeration at 2–8°C for short-term and freezing at -20°C for long-term storage is standard practice reported for peptide powders generally. Prof. Peptide has not identified a manufacturer label, published study, or lab document establishing a specific shelf-life window for sealed research-grade IGF-1 LR3 — this page does not state a duration as fact.
  2. Reconstituted solution: refrigeration at 2–8°C is standard practice once dissolved. Prof. Peptide has not identified a manufacturer label, published study, or lab document establishing how long reconstituted research-grade IGF-1 LR3 remains stable — this page does not state a duration as fact.
  3. Reconstitution uses bacteriostatic water for injection (BAC water). The solvent runs slowly down the glass wall. Swirl gently — do not shake.
  4. The reconstituted solution is never frozen — ice crystals destroy peptide structure.
  5. IGF-1 LR3 is stored protected from light, in the original carton.
  6. A solution that is cloudy, discolored, or contains particles is discarded.

What are the limitations of IGF-1 LR3 research?

IGF-1 LR3 is not FDA-approved for any human use. The recombinant native IGF-1 form (mecasermin/Increlex) is approved for severe primary IGF-1 deficiency in children, but IGF-1 LR3 specifically is not approved for any indication. Most evidence is preclinical; no controlled human trials exist. The World Anti-Doping Agency prohibits IGF-1 LR3 in sport.

IGF-1 LR3 is not FDA-approved for any human use. The recombinant IGF-1 form (mecasermin/Increlex) is FDA-approved for severe primary IGF-1 deficiency in children, but IGF-1 LR3 specifically is not approved for any indication.

Most research evidence comes from animal studies and preclinical research settings. Native IGF-1 has been studied extensively in humans for clinical applications; IGF-1 LR3 specifically has limited human controlled-trial data. Long-term safety data for sustained or high-dose use is absent.

The World Anti-Doping Agency prohibits IGF-1 LR3 in sport under Section S2 (peptide hormones). Research-grade material is sold for laboratory use only and is not approved for human consumption.

Counterfeit and underdosed IGF-1 LR3 is common in the gray market — purity verification via Certificate of Analysis is critical.

IGF-1 LR3 FAQ

How is IGF-1 LR3 different from native IGF-1?

Native IGF-1 has a half-life of minutes because it's rapidly bound and deactivated by IGF binding proteins (IGFBPs). IGF-1 LR3 has two structural modifications — an arginine substitution at position 3 and a 13-amino-acid N-terminal extension — that drastically reduce IGFBP binding. The result: 20–30 hour half-life and ~3x greater potency than native IGF-1.

Does IGF-1 LR3 cause hyperplasia (new muscle fibers)?

Animal studies show IGF-1 LR3 stimulates satellite cell proliferation, which is the cellular basis for hyperplasia (new muscle fiber formation). Hyperplasia is rare among muscle-building compounds — most drive hypertrophy (existing fiber growth) only. Whether this translates to meaningful new fiber formation in adult humans is not formally established, but the satellite cell mechanism is consistent across species.

Why do I need to eat with IGF-1 LR3?

IGF-1 LR3 has insulin-like effects on glucose uptake, which can cause significant blood sugar drops if injected without food. Community-reported practice pairs each injection with a meal containing protein and carbohydrates within 30 minutes, citing that glucose-uptake effect as the reason. Hypoglycemia symptoms (shakiness, sweating, confusion) are the most commonly reported adverse effect when that practice isn't followed.

Should I inject post-workout or pre-workout?

Post-workout is the common community approach. Resistance training creates a temporary spike in growth hormone and increases IGF-1 receptor sensitivity in worked muscles, so injecting within 30–60 minutes post-workout is thought to capitalize on this window. The specific timing figures circulating in the research community are convention — no controlled human trial of the analog has quantified a post-workout advantage.

Do I need post-cycle therapy (PCT)?

No. IGF-1 LR3 doesn't suppress natural testosterone or growth hormone production, so PCT is unnecessary. The only post-cycle consideration is the 4-week off period to allow IGF-1 receptor sensitivity to reset.

Can IGF-1 LR3 be stacked with steroids?

Theoretically yes — they work through different mechanisms (IGF-1 receptor vs androgen receptor). However, this combination significantly increases overall side effect risk and isn't supported by controlled human data. Mainstream peptide research focuses on IGF-1 LR3 as a standalone or paired with other peptides (GH secretagogues, Follistatin) rather than steroids.

Can IGF-1 LR3 be stacked with Follistatin?

Yes — this is one of the most mechanistically complementary stacks. Follistatin removes the myostatin growth ceiling; IGF-1 LR3 provides the growth signal that pushes against it. Often combined in advanced muscle-building protocols, sometimes alongside GH secretagogues. Side-effect risk compounds — careful cycling and dose titration are essential.

Is IGF-1 LR3 safe long-term?

Limited human safety data exists. The best-documented concern is hypoglycemia risk during use; the tumor-growth concern is theoretical (IGF-1's mitogenic action), and on that basis a personal history of malignancy is treated as a theoretical exclusion — no controlled human trial of the analog has measured cancer risk. Most users follow 4–6 week cycles with 4+ week breaks rather than continuous use, both for safety conservatism and to maintain receptor sensitivity.

Where can I buy IGF-1 LR3?

IGF-1 LR3 is sold by specialty research peptide vendors. Counterfeit and underdosed product is common — verify Certificate of Analysis before purchase. PP maintains a list of vetted vendors with verified discount codes — see Verified Discount Codes .

References

  1. Wikipedia. Long arginine 3-IGF-1 (IGF-1 LR3). https://en.wikipedia.org/wiki/IGF-1_LR3
  2. Florini JR, Ewton DZ, Coolican SA. Growth hormone and the insulin-like growth factor system in myogenesis. Endocr Rev. 1996;17(5):481-517. https://pubmed.ncbi.nlm.nih.gov/8897022/
  3. Yakar S, Pennisi P, Wu Y, et al. Circulating levels of IGF-1 directly regulate bone growth and density. J Clin Invest. 2002;110(6):771-81. https://www.jci.org/articles/view/15463
  4. Adams GR, Haddad F. The relationships among IGF-1, DNA content, and protein accumulation during skeletal muscle hypertrophy. J Appl Physiol. 1996;81(6):2509-16. https://pubmed.ncbi.nlm.nih.gov/9018499/
  5. Philippou A, Maridaki M, Halapas A, Koutsilieris M. The role of the insulin-like growth factor 1 (IGF-1) in skeletal muscle physiology. In Vivo. 2007;21(1):45-54. https://pubmed.ncbi.nlm.nih.gov/17354613/
  6. Bikle DD, Tahimic C, Chang W, et al. Role of IGF-I signaling in muscle bone interactions. Bone. 2015;80:79-88. https://pubmed.ncbi.nlm.nih.gov/26453498/
  7. Fernandez AM, Torres-Aleman I. The many faces of insulin-like peptide signalling in the brain. Nat Rev Neurosci. 2012;13(4):225-39. https://pubmed.ncbi.nlm.nih.gov/22430016/
  8. Steeb CB, Lamb J, Shoubridge CA, Tivey DR, Penttila I, Read LC. Systemically but not orogastrically delivered insulin-like growth factor (IGF)-I and long [Arg3]IGF-I stimulates intestinal disaccharidase activity in two age groups of suckling rats. Pediatr Res. 1998;44(5):663-72. https://pubmed.ncbi.nlm.nih.gov/9803447/

Published Studies

Plain-English summaries of the peer-reviewed studies behind the claims above. Click any title to read the source paper.

PMC / Growth Hormone & IGF Research · 2014Open Access
Optimizing IGF-I for Skeletal Muscle Therapeutics →

Philippou A, Barton ER

A comprehensive review of IGF-1 and its analogs for muscle therapeutic applications, directly relevant to understanding IGF-1 LR3’s research context. The paper examines how structural modifications to native IGF-1 — including those that produced IGF-1 LR3 — affect its biological activity, binding protein interactions, and therapeutic potential. It covers the PI3K/Akt/mTOR signaling cascade that drives muscle protein synthesis and explains why reduced binding to IGF-binding proteins (IGFBPs) — IGF-1 LR3’s key modification — produces more sustained and potent anabolic signaling than native IGF-1.

Journal of Molecular Endocrinology · 1992Paywalled
Novel Recombinant Fusion Protein Analogues of IGF-I — Binding-Protein and Receptor Binding Determine Potency →

Francis GL, Ross M, Ballard FJ, et al.

The foundational characterization of recombinant IGF-I analogues, including Long R3 IGF-1. It shows that reducing IGF-1's affinity for its binding proteins (IGFBPs) — the defining modification in IGF-1 LR3 — markedly increases biological potency, because more peptide stays free to bind the IGF-1 receptor. This binding-protein evasion is the mechanistic basis for IGF-1 LR3's more sustained, potent anabolic signaling versus native IGF-1.

Molecular and Cellular Endocrinology · 2018Paywalled
Use of Growth Hormone, IGF-I, and Insulin for Anabolic Purposes — Pharmacological Basis, Detection, and Adverse Effects →

Anderson LJ, Tamayose JM, Garcia JM

A peer-reviewed pharmacological review of growth hormone, IGF-I, and insulin used as anabolic agents in sport. It explains why IGF-I — including long-acting analogues — is prohibited by anti-doping authorities, how it is detected, and its adverse-effect profile, notably hypoglycemia from IGF-I's insulin-like activity. Provides the evidence base for IGF-1 LR3's risk and regulatory status.

Muscle GrowthAnabolicIGF-1Research-Grade

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