💉 GH Secretagogue • GHSR-1a Agonist

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.

Type Pentapeptide MW ~711.9 Da CAS 170851-70-4 🚫 WADA Prohibited List — S2 Growth hormone secretagogues including ipamorelin are prohibited at all times in sport. Researchers working with athlete populations must refer to current antidoping rules.

⚡ 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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01 Overview 02 Properties 03 Mechanism 04 Selectivity 05 Handling 06 Comparison 📋

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

• 📈 Pulsatile GH — brief, physiologic-like pulse
• ✓ Selective — minimal ACTH/cortisol
• ⏱️ Short-acting — ~2h half-life

⏱️ Pharmacokinetic Profile (Human)

0 min Administration → ~40 min GH Peak → ~2 h Peptide t½ → Baseline Return

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
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.

↑ GH Growth Hormone Robust, pulsatile release via GHSR-1a — ACTH ACTH / Cortisol Minimal effect even at >200× GH ED50 — PRL Prolactin No significant elevation vs. GHRPs ± Appetite Appetite Effects Less than GHRP-6; variable reports ⚠️

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 quality documentation, and applicable regulations. The steps below are educational and not medical advice.

1

Verify Identity

Confirm peptide name, lot, mass, purity on quality documentation. Check CAS 170851-70-4, UNII Y9M3S784Z6.

2

Plan Concentration

5 mg + 2.0 mL = 2.5 mg/mL; 10 mg + 4.0 mL = 2.5 mg/mL. Document calculations.

3

Choose Diluent

Bacteriostatic Water for Injection, USP (0.9-1.1% benzyl alcohol) for multi-dose. Not for neonates.

4

Reconstitute Gently

Room temp; inject diluent along glass wall; swirl (don’t shake) — peptides can aggregate under stress.

5

Label & Store

Record compound, lot, concentration, date. Lyophilized: ≤ −20°C; solutions: 2–8°C short-term or freeze aliquots.

6

Dispose Responsibly

Follow hazardous waste and biosafety procedures. Document disposal in lab records.

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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

GHSR-1a Agonist (Pentapeptide) Short Pulse ~2h t½

Selective GH pulse. Peak ~40 min. Minimal ACTH/cortisol even at high doses. Targeted lever vs. broad faucet.

GHRP-6 / GHRP-2

GHSR-1a Agonists Pulsatile

Broader endocrine signal. Often increases ACTH/cortisol & prolactin, especially IV/high dose. Appetite stimulation common.

CJC-1295 (DAC)

GHRH Analogue (Long-Acting) Sustained ~6-9d t½

Long persistence. Sustained GH/IGF-1 elevation over days-weeks via GHRH receptor. Align with study aims.

MK-677 (Ibutamoren)

Oral GHS Mimetic Oral Daily 24h Effect

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

What is Ipamorelin? A selective growth hormone secretagogue that activates the ghrelin receptor (GHSR-1a) to produce a brief, physiologic-like GH pulse. It’s a pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH₂) designed to maximize GH selectivity vs. older GHRPs. How long does Ipamorelin last? GH effect peaks at ~40 minutes (0.67 hours) with a peptide half-life of ~2 hours. The GH rise is episodic and declines back to baseline thereafter — a short-acting profile. Does it affect cortisol like GHRP-6? No — Ipamorelin did not increase ACTH/cortisol above GHRH-like levels in animal studies even at >200× its GH ED50, whereas GHRP-6 and related agents can raise ACTH/cortisol and prolactin. Can it combine with CJC-1295? Ghrelin-pathway agonism (GHSR-1a) and GHRH signaling are mechanistically complementary. Literature describes synergy between ghrelin and GHRH on GH release. Research designs must weigh pulse timing vs. sustained exposure. Is Ipamorelin permitted in sport? No. Growth hormone secretagogues including ipamorelin are on the WADA Prohibited List at all times (S2). Researchers working with athlete populations must refer to current antidoping rules. What risks should be monitored? 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. ✅

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.