Ipamorelin (NNC 26-0161)
Selective pentapeptide ghrelin receptor agonist that triggers pulsatile GH release with minimal impact on ACTH/cortisol. Short-acting (~2h half-life) with peak effect at ~40 minutes.
⚡ Executive Summary
Ipamorelin is a pentapeptide ghrelin-receptor agonist that selectively stimulates pulsatile GH release without measurably raising ACTH/cortisol in animal models. In humans, it produces a short-acting GH pulse (peak ≈ 40 min; peptide t½ ≈ 2 hours). Think of it as a “precision tap” on the GH axis — brief, focused pulses with less off-target pituitary noise than older GHRPs.
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Overview
💉 What is Ipamorelin?
Ipamorelin is a selective growth hormone secretagogue (GHS) that activates GHSR-1a (the ghrelin receptor) to induce GH release.
It’s the first selective GHS — sparing other pituitary axes (ACTH/cortisol) in animal models even at very high doses.
🎯 Key Features
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Pulsatile GH — brief, physiologic-like pulse
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Selective — minimal ACTH/cortisol
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Short-acting — ~2h half-life
⏱️ Pharmacokinetic Profile (Human)
Single GH episode peaking at ~0.67 hours with peptide terminal half-life near 2 hours
Key insight: Think of ipamorelin as a “precision tap” on the GH axis. Where GHRP-6 acts like a broad faucet (GH + neuroendocrine spillover), ipamorelin behaves like a targeted lever: brief, focused GH pulses with less off-target pituitary noise.
Entity Properties
| Aliases | Ipamorelin, NNC 26-0161, UNII: Y9M3S784Z6 |
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| Sequence | Aib-His-D-2-Nal-D-Phe-Lys-NH₂ |
| Length | 5 amino acids (pentapeptide) |
| Molecular Weight | ~711.9 Da |
| CAS Number | 170851-70-4 |
| Target | GHSR-1a (Ghrelin receptor) |
| Family | Growth hormone secretagogue (GHS) |
| Diluent(s) | Bacteriostatic Water for Injection, USP (0.9-1.1% benzyl alcohol) |
| Concentration | 5 mg + 2 mL = 2.5 mg/mL; 10 mg + 4 mL = 2.5 mg/mL (example) |
| Storage (dry) | ≤ −20°C, protected from light; stable long-term |
| Storage (solution) | 2–8°C short-term; freeze aliquots for longer storage |
Mechanism of Action
🧠 How does Ipamorelin work?
Ipamorelin activates GHSR-1a, a GPCR expressed in pituitary somatotrophs and hypothalamic circuits. Endogenous ghrelin boosts GH by synergizing with GHRH and counteracting somatostatin’s inhibitory tone.
This explains why GHSs can augment rather than replace physiologic pulsatility — they amplify the existing rhythm rather than override it.
🎯 GHSR-1a Binding
Activates ghrelin receptor on pituitary somatotrophs to trigger GH release
🤝 GHRH Synergy
Works with GHRH pathway — complementary mechanisms for GH pulse amplification
🛡️ Somatostatin Counter
Helps overcome somatostatin’s inhibitory tone on GH secretion
Timing matters: In adults, 60–70% of daily GH secretion clusters after sleep onset with slow-wave sleep. Researchers sometimes align short-acting GHS administration with times that do not blunt natural nocturnal pulses — the goal is to support rather than flatten physiologic rhythms.
Selectivity Profile
📊 Ipamorelin vs. Older GHRPs
Classic GHRPs (e.g., GHRP-6, hexarelin) can raise ACTH, cortisol, and prolactin, especially with IV or high exposure. Ipamorelin showed minimal ACTH/cortisol effects in animal tests at doses >200× its GH ED50 — an important distinction for interpreting endocrine “side-signal” noise.
Research context: GH pathway modulation can relate to fluid retention, paresthesias, arthralgia, insulin sensitivity shifts, and lipid changes — particularly when exposure is sustained. Monitor relevant endpoints in study designs.
Research Handling
Research use only. Follow your institution’s SOPs, the product’s COA, and applicable regulations. The steps below are educational and not medical advice.
Verify Identity
Confirm peptide name, lot, mass, purity on COA. Check CAS 170851-70-4, UNII Y9M3S784Z6.
Plan Concentration
5 mg + 2.0 mL = 2.5 mg/mL; 10 mg + 4.0 mL = 2.5 mg/mL. Document calculations.
Choose Diluent
Bacteriostatic Water for Injection, USP (0.9-1.1% benzyl alcohol) for multi-dose. Not for neonates.
Reconstitute Gently
Room temp; inject diluent along glass wall; swirl (don’t shake) — peptides can aggregate under stress.
Label & Store
Record compound, lot, concentration, date. Lyophilized: ≤ −20°C; solutions: 2–8°C short-term or freeze aliquots.
Dispose Responsibly
Follow hazardous waste and biosafety procedures. Document disposal in lab records.
Comparison
Ipamorelin is the most selective GH-centric secretagogue among first-generation GHRPs. Longer-acting options change the timing of GH/IGF-1 exposure, while oral MK-677 increases 24-h GH/IGF-1 with appetite and metabolic effects.
Ipamorelin
Selective GH pulse. Peak ~40 min. Minimal ACTH/cortisol even at high doses. Targeted lever vs. broad faucet.
GHRP-6 / GHRP-2
Broader endocrine signal. Often increases ACTH/cortisol & prolactin, especially IV/high dose. Appetite stimulation common.
CJC-1295 (DAC)
Long persistence. Sustained GH/IGF-1 elevation over days-weeks via GHRH receptor. Align with study aims.
MK-677 (Ibutamoren)
Elevated 24-h GH/IGF-1. ↑ FFM but also ↑ weight, appetite. Modest cortisol ↑. Glucose/insulin shifts in older adults.
Best choice? For research requiring brief, targeted GH pulses with minimal endocrine spillover, ipamorelin is the selective pick. For sustained GH/IGF-1 elevation, consider CJC-1295 or MK-677 depending on route preference.
FAQ
Bottom line: Ipamorelin is best understood as a short-acting, GH-selective “pulse tool” via GHSR-1a — useful for research questions where timing and endocrine selectivity matter. Its minimal ACTH/cortisol impact distinguishes it from older GHRPs, making it a precision instrument for GH axis research. Educational use only.