The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration. — VialBase Research

Summary

This 2026 narrative review from Poznan University of Medical Sciences examines the growing use of unregulated “research compound” peptides that modulate the growth hormone-insulin-like growth factor-1 (GH-IGF-1) axis, a category spanning GHRH analogues (sermorelin, tesamorelin, CJC-1295 with/without DAC), growth hormone secretagogues (GHRP-2, GHRP-6, hexarelin, and ipamorelin), the GH fragment AOD9604, and IGF-1 analogues (PEG-MGF, IGF-1 LR3). The authors stratify these agents into evidence tiers ranging from regulatory-grade randomized trial data down to a complete absence of human studies, explicitly contrasting peer-reviewed pharmacokinetic/pharmacodynamic and clinical evidence with the dosing protocols circulating in online self-administration communities. Because none of these peptides carry regulatory approval for performance or physique-related indications, and because product composition, dosing, and stacking practices in unregulated supply chains remain uncertain, the review synthesizes clinically relevant adverse effects — including prolactin and cortisol elevations, appetite changes, dysglycaemia, fluid retention, myalgia/arthralgia, and injection-site reactions — that clinicians should watch for in self-administering patients. It also flags biologically plausible but unproven mitogenic concerns tied to IGF-1 axis activation. The review closes with a clinically oriented assessment algorithm for exposure history-taking, symptom-domain triage, and risk communication, intended to help clinicians engage with patients without legitimising off-label peptide use.

Key Findings

• PEDs marketed as “research compounds” encompass unregulated peptides modulating the GH-IGF-1 axis, including GH secretagogues (GHRP-2, GHRP-6, hexarelin, ipamorelin), GHRH analogues (sermorelin, tesamorelin, CJC-1295 with/without DAC), the GH fragment AOD9604, and IGF-1 analogues (PEG-MGF, IGF-1 LR3).
• The review stratifies these agents into evidence tiers ranging from regulatory-grade randomized trial data down to a complete absence of human studies, exposing substantial uncertainty around claimed performance and body-recomposition benefits.
• Reported adverse effects span endocrine-metabolic disturbances (prolactin and cortisol elevations, appetite changes, dysglycaemia), fluid retention syndromes, musculoskeletal symptoms (myalgia/arthralgia), and injection-site reactions.
• The authors explicitly contrast peer-reviewed pharmacokinetic/pharmacodynamic and clinical evidence against commonly encountered online self-administration protocols, citing the absence of regulatory approval for performance/physique use and uncertainty around product composition, dosing, and stacking in unregulated supply chains.
• The review proposes a clinically oriented assessment algorithm for exposure history-taking, symptom-domain triage, and risk communication, intended to help clinicians engage self-administering patients without legitimising off-label peptide regimens.

Relevance to Ipamorelin

Ipamorelin is named directly among the growth hormone secretagogues — alongside GHRP-2, GHRP-6, and hexarelin — that this review places within its evidence-tiering framework, contrasting peer-reviewed pharmacokinetic/pharmacodynamic and clinical data against the dosing protocols that circulate in online self-administration communities. The abstract does not report ipamorelin-specific trial results or dosing figures; its core contribution for ipamorelin users is instead the caution that GHS-class peptides are being self-administered well ahead of confirmed human efficacy evidence, with genuine uncertainty about product composition, dose, and stacking practices in unregulated supply chains. The adverse-effect profile the review synthesizes — endocrine-metabolic disturbances, fluid retention, musculoskeletal symptoms, and injection-site reactions — is presented as relevant across the GHS class and gives clinicians a framework for interpreting symptoms in patients using ipamorelin, though the review does not isolate which effects are specific to ipamorelin versus other secretagogues. This should be read as a call for clinical vigilance and a documented evidence gap, not as new efficacy or safety data on ipamorelin itself.

Citation

Dominikowski A, Rękoś Z, Olejarz M, et al. The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration. Frontiers in Endocrinology. 2026;17:1822475. doi:10.3389/fendo.2026.1822475.

See Also

• Parent compound: Ipamorelin