Ipamorelin is a pentapeptide growth hormone secretagogue first described by Raun et al. in 1998. It belongs to the broader class of GHRPs (growth hormone releasing peptides) alongside GHRP-2, GHRP-6, and hexarelin — but its distinguishing feature is selectivity. This overview maps the published research on how ipamorelin produces GH pulses without the side-arm activations seen with older GHRPs.
Sequence and structure
Ipamorelin: Aib-His-D-2-Nal-D-Phe-Lys-NH₂. The unnatural amino acids (Aib, D-2-Nal, D-Phe) protect against enzymatic degradation and tune receptor selectivity. The C-terminal amide is required for ghrelin receptor binding.
Receptor target — GHS-R1a
Ipamorelin is a selective agonist of the growth hormone secretagogue receptor 1a (GHS-R1a) — the same receptor activated by endogenous ghrelin. Binding triggers a downstream cascade that releases pulsatile growth hormone from anterior pituitary somatotrophs.
What “selective” means in practice
Older GHRPs (GHRP-2, GHRP-6) activate GHS-R1a but also produce off-target hormonal shifts. The research literature reports:
- GHRP-2: significant ACTH and cortisol release alongside GH
- GHRP-6: prolactin, ACTH, and cortisol elevation; potent appetite stimulation via central pathways
- Ipamorelin: GH release without measurable ACTH, cortisol, or prolactin elevation in most research models (Raun et al., 1998)
The selectivity comes from molecular structure differences that engage GHS-R1a tightly while avoiding cross-reactivity at related receptors.
Pulse pharmacokinetics
Ipamorelin has a short plasma half-life (~2 hours) and produces a fast-rising, relatively brief GH pulse — typically peaking 15–30 minutes after administration in research models and returning to baseline within 2–3 hours. This mimics the pulsatile pattern of endogenous GH release rather than producing a sustained elevation.
Combination research — ipamorelin + CJC-1295
Ipamorelin is frequently paired with CJC-1295 (a GHRH analogue) in research protocols. The two act on different receptors: CJC-1295 amplifies the underlying GHRH signal while ipamorelin provides the ghrelin-receptor pulse. Synergistic GH release amplitude is reported in rodent models, but caution: the literature on combination protocols is preclinical and combination dosing has not been systematically validated in human trials.
Stability and reconstitution
Ipamorelin is supplied lyophilised. Reconstitution in bacteriostatic water at 2–5 mg/mL is typical for stability studies. Refrigerated, reconstituted ipamorelin retains potency for approximately 28 days. Avoid freeze-thaw cycles — the short pentapeptide is sensitive to repeated phase transitions.
Open research questions
- Long-term receptor desensitisation patterns under chronic dosing
- Comparative selectivity profile in human vs rodent pituitary cells
- Interaction effects with food intake (ghrelin is endogenously suppressed postprandially)
Chempeptides supplies HPLC-verified ipamorelin with batch CoA — see the research catalogue for current availability and our reconstitution guide for protocol detail.
Research use only.