tuneTypical Dose
20-100 µg/day SC (protocol-only, highly individualized)
Peptide
IGF-1 LR3
Insulin-like growth factor 1 long-acting analog 3
Evidence TierCWADA PROHIBITED
watchEffect Window
Acute biomarker effects can appear within hours to days. Durable functional outcomes are uncertain.
lockCompliance
WADA PROHIBITED
Overview
Clinical Summary
IGF-1 LR3 is a long-acting insulin-like growth factor 1 analog used experimentally. It is discussed for anabolic and tissue repair effects, but published evidence is largely preclinical rather than human.
IGF-1 biology supports roles in muscle protein synthesis and tissue repair, but controlled human evidence for meaningful functional gains is lacking. The published LR3-specific literature is mostly preclinical, including fetal sheep and laboratory analog-design work rather than wellness trials. Risks include altered glucose regulation and concerns related to proliferative signaling. Benefits remain speculative without rigorous trials defining safety and effectiveness.
IGF-1 receptor pathway stimulation with prolonged exposure profile than native IGF-1 in some protocol contexts.
Outcomes
What This Is Expected To Influence
Primary Outcomes
- IGF-1 axis activation
- Short-horizon recovery/symptom proxies
Secondary Outcomes
- Body composition trend
- Glucose/metabolic tolerance
- Safety/monitoring burden
Safety
Contraindications and Interactions
Contraindications
- Active cancer
- History of malignancy requiring active surveillance
- Pregnancy
- Lactation
- Brittle diabetes
- Severe unstable endocrine disease
- Active anti-doping obligations
Side effects
- Hypoglycemia
- Joint pain
- Jaw/hand growth
- Organ enlargement risk
Interactions
- Insulin
- Sulfonylureas
- High-dose glucocorticoids
- Concurrent GH/IGF axis compounds
- Compounded investigational peptides
Avoid if
- Minors
- Pregnant or attempting to conceive
- Uncontrolled diabetes
- History of serious endocrine neoplasia
- Unreliable access chain
Evidence
Study-level References
igf-1-lr3-SRC-001Preclinical protein-engineering study
Sourceopen_in_newBryant KJ et al. 1996. "Design and characterisation of long-R3-insulin-like growth factor-I muteins which show resistance to pepsin digestion." Growth Factors. 13(3-4):261-272. PMID: 8919033. DOI: 10.3109/08977199609003227.
Population: Laboratory peptide-design and digestion-resistance experiments.
Dose protocol: Laboratory analog-design and digestion-resistance testing.
Key findings: Foundational long-R3-IGF-I work explains why the analog persists longer and maintains growth-promoting activity compared with less modified forms.
Notes: Mechanistic design paper only. It does not establish human benefit.
Paper content
Foundational preclinical work describing why long-R3-IGF-I remains active longer than native IGF-1 analogs, which is useful for mechanism framing but does not support human efficacy.
igf-1-lr3-SRC-002Preclinical controlled infusion study
Sourceopen_in_newWhite A et al. 2025. "IGF-1 LR3 does not promote growth in late-gestation growth-restricted fetal sheep." Am J Physiol Endocrinol Metab. 328(1):E116-E125. PMID: 39679943. DOI: 10.1152/ajpendo.00259.2024.
Population: Late-gestation fetal sheep with placental-insufficiency-associated growth restriction.
Dose protocol: 1 week direct fetal-circulation infusion at roughly 1.17 μg/kg/h in growth-restricted fetal sheep.
Key findings: IGF-1 LR3 did not improve growth in growth-restricted fetal sheep and reduced circulating amino acids.
Notes: Direct LR3 physiology signal, but still a nonhuman study.
Paper content
In growth-restricted fetal sheep, 1 week of IGF-1 LR3 did not improve growth or glucose-stimulated insulin secretion, but circulating amino acids fell, reinforcing a meaningful metabolic-monitoring burden without a demonstrated anabolic benefit.
igf-1-lr3-SRC-003Preclinical controlled acute-infusion study
Sourceopen_in_newWhite A et al. 2023. "Attenuated glucose-stimulated insulin secretion during an acute IGF-1 LR3 infusion into fetal sheep does not persist in isolated islets." J Dev Orig Health Dis. 14(3):353-361. PMID: 37114757. DOI: 10.1017/S2040174423000090.
Population: Late-gestation fetal sheep undergoing acute IGF-1 LR3 or vehicle infusion, with isolated-islet follow-up assays.
Dose protocol: Acute 90-minute infusion with hyperglycemic clamp and isolated-islet follow-up.
Key findings: IGF-1 LR3 acutely suppressed glucose-stimulated insulin secretion in vivo, although isolated islets recovered ex vivo.
Notes: Important metabolic risk signal. Still nonhuman and not a performance study.
Paper content
Acute IGF-1 LR3 exposure suppressed in vivo insulin secretion during a hyperglycemic clamp, but the isolated islets recovered ex vivo, suggesting a meaningful short-term metabolic effect without evidence of durable anabolic benefit.
igf-1-lr3-SRC-004Preclinical controlled infusion study
Sourceopen_in_newWhite A et al. 2025. "IGF-1 LR3 does not promote growth in late-gestation growth-restricted fetal sheep." Am J Physiol Endocrinol Metab. 328(1):E116-E125. PMID: 39679943. DOI: 10.1152/ajpendo.00259.2024.
Population: Late-gestation fetal sheep with placental-insufficiency-associated growth restriction.
Dose protocol: Heterogeneous dosing and route patterns
Key findings: Reported outcomes are inconsistent. Many findings are signal-level only.
Notes: Highlights need for protocol harmonization and endpoint standardization.
Paper content
In growth-restricted fetal sheep, 1 week of IGF-1 LR3 did not improve growth or glucose-stimulated insulin secretion, but circulating amino acids fell, reinforcing a meaningful metabolic-monitoring burden without a demonstrated anabolic benefit.
igf-1-lr3-SRC-005Preclinical controlled acute-infusion study
Sourceopen_in_newWhite A et al. 2023. "Attenuated glucose-stimulated insulin secretion during an acute IGF-1 LR3 infusion into fetal sheep does not persist in isolated islets." J Dev Orig Health Dis. 14(3):353-361. PMID: 37114757. DOI: 10.1017/S2040174423000090.
Population: Late-gestation fetal sheep undergoing acute IGF-1 LR3 or vehicle infusion, with isolated-islet follow-up assays.
Dose protocol: Variable protocol exposures without long-duration harmonized endpoints
Key findings: Strong signal quality for acute endocrinologic change does not equate to durable functional evidence.
Notes: Emphasizes uncertainty and safety-follow-up insufficiency.
Paper content
Acute IGF-1 LR3 exposure suppressed in vivo insulin secretion during a hyperglycemic clamp, but the isolated islets recovered ex vivo, suggesting a meaningful short-term metabolic effect without evidence of durable anabolic benefit.
igf-1-lr3-SRC-006Regulatory list and compliance documentation
Sourceopen_in_newUSADA explains IGF-1 is prohibited on the WADA Prohibited List as an exogenous growth factor class substance (PMID: not applicable; https://www.usada.org/spirit-of-sport/igf-1-and-the-world-anti-doping-agency-prohibited-list/)
Population: Competitive-athlete governance context
Dose protocol: N/A
Key findings: Compliance risk is clear even when mechanism evidence is incomplete.
Notes: Regulatory context should be treated as hard constraints for athletes.
Paper content
Compliance risk is clear even when mechanism evidence is incomplete.
igf-1-lr3-SRC-007Regulatory safety communication
Sourceopen_in_newFDA compounding risk alerts; unapproved drugs are not held to the same safety/quality standards as approved products (https: //www.fda.gov/drugs/human-drug-compounding/compounding-risk-alerts) and associated warning-letter enforcement context for peptide products (https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/united-pharmacy-553916-02112019)
Population: U.S. distribution and practice context
Dose protocol: N/A
Key findings: Quality variability and monitoring uncertainty are meaningful implementation barriers.
Notes: Supports stricter sourcing and oversight standards.
Paper content
Quality variability and monitoring uncertainty are meaningful implementation barriers.
igf-1-lr3-SRC-008Preclinical controlled infusion study
Sourceopen_in_newWhite A et al. 2025. "IGF-1 LR3 does not promote growth in late-gestation growth-restricted fetal sheep." Am J Physiol Endocrinol Metab. 328(1):E116-E125. PMID: 39679943. DOI: 10.1152/ajpendo.00259.2024.
Population: Late-gestation fetal sheep with placental-insufficiency-associated growth restriction.
Dose protocol: Variable exposure contexts
Key findings: Hypoglycemia and glucose instability remain clinically important monitoring concerns.
Notes: Direct causality is often context-dependent. Still relevant for safety-by-design.
Paper content
In growth-restricted fetal sheep, 1 week of IGF-1 LR3 did not improve growth or glucose-stimulated insulin secretion, but circulating amino acids fell, reinforcing a meaningful metabolic-monitoring burden without a demonstrated anabolic benefit.