GHRP-2 vs IGF-1 LR3

Synthetic hexapeptide that stimulates pulsatile growth hormone release from the anterior pituitary by acting on the ghrelin receptor (GHSR-1a). Commonly stacked with GHRH analogs such as CJC-1295 or Sermorelin to amplify GH output synergistically.

GHRP-2 (growth hormone-releasing peptide-2; pralmorelin; KP-102) is a synthetic hexapeptide (D-Ala-D-2Nal-Ala-Trp-D-Phe-Lys-NH2) and potent ghrelin receptor (GHS-R1a) agonist developed as a GH secretagogue with established efficacy in stimulating pulsatile GH release from pituitary somatotrophs, characterized by potent GH stimulation alongside non-selective co-stimulation of cortisol and prolactin secretion. As a first-generation GHRP, GHRP-2 achieves its GH-secretory effect through direct GHS-R1a agonism with amplification by endogenous GHRH; it is distinguished from later selective GHRPs such as ipamorelin by its non-selective endocrine profile, and synergistic GH stimulation is observed when combined with GHRH analogs in diagnostic protocols. GHRP-2 has been validated as a diagnostic agent for the GHRP-2 stimulation test used in Japan to assess GH secretion capacity in adults with suspected hypopituitarism or post-surgical pituitary dysfunction, with published human clinical data supporting its reliability as a GH stimulation tool in endocrine diagnostic practice. GHRP-2 has no FDA approval for any therapeutic or diagnostic indication in the United States; it is used diagnostically in Japan and as a research compound elsewhere, with no approved indication for GH enhancement, performance, or anti-aging applications, and its non-selective endocrine stimulation profile represents a relevant consideration versus more selective GH secretagogues. GHRP-2 dosage in research contexts: doses of 100–300 mcg per subcutaneous injection are documented across research protocols, typically administered 2–3 times daily. Co-administration with a GHRH analog (such as CJC-1295 or sermorelin) produces synergistic GH release and is studied in combination protocols for this reason. Administration is by subcutaneous injection following reconstitution with bacteriostatic water. GHRP-2 vs GHRP-6 vs ipamorelin: GHRP-2 produces potent GH release but with co-stimulation of cortisol and prolactin, similar to GHRP-6. The key distinguishing feature of GHRP-6 is stronger appetite stimulation (ghrelin-like effect); GHRP-2 produces less appetite stimulation with comparable or slightly greater GH output per dose. Both are non-selective compared to ipamorelin, which was developed specifically to achieve GH stimulation without the cortisol and prolactin co-elevation that characterizes first-generation GHRPs. For research contexts prioritizing GH selectivity, ipamorelin is generally preferred; GHRP-2 is used where its diagnostic validation and potent GH stimulation profile are the research objectives.

Long-acting analog of IGF-1 that binds to IGF-1 receptors, promoting muscle protein synthesis, cellular growth, and recovery. Suppresses myostatin activity and has a significantly extended half-life compared to native IGF-1 due to reduced binding protein affinity.

IGF-1-LR3 (Long Arg3 IGF-1) is a synthetic 83-amino-acid analog of insulin-like growth factor 1, engineered with an N-terminal 13-amino-acid extension and an Arg3 substitution that substantially reduces binding to IGF-binding proteins (IGFBPs), resulting in a biological half-life approximately 120 times longer than native IGF-1 and theoretically greater receptor availability in peripheral tissues. The reduced IGFBP affinity means a higher proportion of circulating IGF-1-LR3 remains unbound and potentially bioactive; in vitro cell proliferation studies and animal models suggest amplified anabolic signaling relative to equimolar native IGF-1, and the compound is widely used as a research reagent in cell culture for controlled IGF-1R stimulation without the confounding effects of endogenous binding protein dynamics. No human pharmacokinetic, safety, or efficacy studies of IGF-1-LR3 have been published in PubMed-indexed journals; the indexed scientific literature consists of in vitro proliferation studies, animal metabolic research, and anti-doping detection methods — a complete absence of clinical data supporting or characterizing its use in humans. IGF-1-LR3 has no FDA approval or regulatory approval in any jurisdiction; it is a research laboratory reagent and non-approved analog available through research chemical suppliers, and the complete absence of published human data means its pharmacological behavior, tissue distribution, and safety profile in humans are entirely uncharacterized. IGF-1 LR3 in research contexts: as a laboratory reagent, IGF-1-LR3 is used at nanomolar concentrations in cell culture assays to stimulate IGF-1 receptor signaling. The extended half-life (approximately 20–30 hours compared to native IGF-1's 15 minutes) is the primary reason for its use in research settings requiring sustained IGF-1R activation. In animal pharmacology studies, doses vary widely by species and model; these cannot be directly extrapolated to human dosing, and no safe or effective human dose has been established. Its extended half-life relative to native IGF-1 is also the property most frequently cited in anti-doping detection literature, where the compound has been identified in biological samples from competitive athletes. The absence of any human clinical data distinguishes IGF-1-LR3 from growth hormone secretagogues such as sermorelin, ipamorelin, or MK-677, which have documented human pharmacological profiles. Providers offering researched GH-axis peptides with clinical datasets are listed in the PeptideBase directory.