Ipamorelin
The selective ghrelin-receptor peptide — known for its clean GH pulse without spillover into cortisol or prolactin.
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What Is Ipamorelin?
Ipamorelin is a pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH₂) developed by Novo Nordisk in the late 1990s. It belongs to the growth-hormone-releasing peptide (GHRP) class — a family of synthetic ghrelin-receptor agonists that includes GHRP-2, GHRP-6, and hexarelin.
What set ipamorelin apart from earlier GHRPs was its receptor selectivity. Older GHRPs released GH but also raised cortisol, prolactin, and hunger signals. Ipamorelin produces a comparable GH pulse with negligible effect on those off-target hormones, making it the cleanest GHRP in the class for long-term research use.
Ipamorelin is most commonly studied in combination with a GHRH analog like CJC-1295, where the two peptides act synergistically — GHRH increases the amplitude of the GH pulse while ipamorelin amplifies the number of releasing somatotrophs. This combination is the dominant research stack in the GH-secretagogue space.
History & Discovery
Ipamorelin was synthesized by Novo Nordisk in the late 1990s as part of a deliberate medicinal-chemistry program to find a pure GH-releasing peptide free of the off-target effects that plagued earlier GHRPs. The starting point was GHRP-1, a hexapeptide with strong GH-releasing activity but significant cortisol and prolactin elevation.
Researchers truncated, modified, and screened pentapeptide variants until landing on Aib-His-D-2-Nal-D-Phe-Lys-NH₂ — the structure that became ipamorelin. In screening assays, ipamorelin produced a GH pulse comparable to GHRP-6 with cortisol and prolactin responses indistinguishable from baseline.
Despite a clean preclinical profile, Novo Nordisk did not advance ipamorelin to a registration program — the company shifted strategic focus to incretin-class compounds (the work that ultimately produced semaglutide). Ipamorelin entered the research-peptide ecosystem and quickly became the dominant GHRP for stacked GH-axis research.
The ipamorelin + CJC-1295 stack — pairing a clean GHRP with a modified GHRH analog — emerged in the early 2010s as the de facto standard configuration for research investigating endogenous GH pulse amplification.
Mechanism of Action
Ipamorelin binds the growth hormone secretagogue receptor (GHSR-1a) on the anterior pituitary — the same receptor activated by endogenous ghrelin. Activation triggers a calcium-dependent release of stored growth hormone from somatotroph cells.
Unlike ghrelin itself, ipamorelin has been engineered to be selective for the GH-releasing arm of the receptor without significantly activating the appetite-stimulating, cortisol-raising, or prolactin-elevating pathways. This selectivity is the principal reason it is favored over GHRP-6 (which causes pronounced hunger) and GHRP-2 (which can elevate cortisol).
When stacked with a GHRH analog, the two mechanisms are complementary: GHRH primes somatotrophs to release GH, ipamorelin amplifies the size of that release, and the combined pulse is larger than either peptide alone — while still respecting somatostatin-mediated negative feedback.
Pharmacokinetics
| Molecular weight | 711.85 Da |
| Sequence | Aib-His-D-2-Nal-D-Phe-Lys-NH₂ (pentapeptide) |
| Receptor target | GHSR-1a (ghrelin receptor) — selective for GH-releasing arm |
| Time to peak GH (Tmax) | ~30 minutes after subcutaneous injection |
| Half-life (T½) | Approximately 2 hours |
| Cortisol effect | Negligible at standard research doses |
| Prolactin effect | Negligible at standard research doses |
| ACTH effect | Negligible (in contrast to GHRP-2 and GHRP-6) |
Research Use Cases
Pulsatile GH Restoration
The core research application — restoring a youthful GH pulse pattern in adults experiencing somatopause without exogenous rhGH administration.
Body Composition Research
Studied for lean mass preservation and adipose reduction, particularly in stacked GHRH+GHRP protocols. Effect size is modest compared to rhGH but with a more favorable side-effect profile.
Sleep Quality and Slow-Wave Sleep
Evening administration is associated with restored slow-wave sleep architecture, consistent with the broader GH-axis literature.
Recovery and Connective Tissue
Investigated for tendon, ligament, and joint repair contexts, where GH and IGF-1 elevations support collagen synthesis.
Bone Mineral Density
Long-term GH-axis stimulation has been studied for effects on osteoblast activity and bone turnover markers in aging populations.
Cortisol-Sparing GH Stimulation
The selectivity profile makes ipamorelin a preferred research tool when isolating GH effects from HPA-axis confounds.
Research Dosing Reference
Standard research dose — solo
The dose-response curve plateaus around 300 mcg for most research subjects — higher doses do not meaningfully increase the GH pulse.
Standard research stack (with CJC-1295 no-DAC)
The dominant research configuration. Often referred to simply as 'CJC/Ipa' in research write-ups.
Body composition research — saturation schedule
Used in research contexts where maximal pulse frequency is the design goal.
Recovery/connective-tissue research
Schedule examined in research populations targeting tendon/ligament repair endpoints.
Stacking & Combinations
Ipamorelin + CJC-1295 (no-DAC)
The canonical stack. CJC-1295 (a GHRH analog) primes somatotrophs to release GH; ipamorelin (a GHRP) amplifies the size of that release through the parallel ghrelin-receptor pathway. Combined GH pulse is roughly 2–4× that of either compound alone, with no significant additive side-effect burden.
Ipamorelin + Tesamorelin
Pairs the cleanest GHRP with the only FDA-approved GHRH analog. Less commonly studied than the CJC stack due to tesamorelin's higher cost, but mechanistically similar — the GHRH-priming + GHRP-amplification synergy applies to any GHRH analog.
Ipamorelin + BPC-157
Investigated in connective-tissue recovery research. Ipamorelin provides the systemic GH/IGF-1 elevation; BPC-157 provides the local angiogenic and pro-healing modulation. The mechanisms are entirely complementary — no published trial data, but a common research configuration.
Ipamorelin + Sermorelin
Functionally equivalent to the CJC-1295 stack but with sermorelin as the GHRH partner. Sermorelin's shorter half-life makes timing more critical — the two peptides should be drawn and injected together.
Side Effect Profile
Common / Mild-to-Moderate
- •Mild flushing or warmth in the first 5–10 minutes after injection
- •Transient lightheadedness shortly after injection (usually resolves within minutes)
- •Injection-site reactions — minor redness or itching
- •Mild water retention in the first 1–2 weeks of consistent dosing
- •Vivid dreams or altered sleep architecture (an expected effect of GH-axis stimulation, not pathological)
- •Numbness or tingling in the extremities (GH-axis carpal-tunnel-like effects, dose-related)
Serious / Less Common
- •Glycemic dysregulation in predisposed subjects (less pronounced than tesamorelin or rhGH)
- •Hypersensitivity reactions (rare)
- •Theoretical concern: contraindicated in active malignancy due to GH/IGF-1 elevation
Ipamorelin's selectivity is its principal safety advantage over older GHRPs — the absence of meaningful cortisol, prolactin, or aldosterone elevation is the reason it became the dominant GHRP for research use. Long-term human safety data is limited; standard research practice includes periodic IGF-1 and fasting glucose monitoring.
Storage & Reconstitution
- Lyophilized vials are stored refrigerated at 2–8°C. Vials can typically be kept at room temperature for short shipping intervals without degradation.
- Reconstitute with bacteriostatic water for injection. For a 5 mg vial, 1.25 mL or 2 mL are common volumes — yielding 4 mg/mL or 2.5 mg/mL respectively.
- Inject the BAC water against the vial wall slowly. Swirl gently — never shake — until fully dissolved.
- Once reconstituted, store refrigerated. Stable for approximately 30 days for research purposes; many users replace the vial sooner to maintain consistent potency.
- Ipamorelin is commonly drawn and injected together with CJC-1295 in the same syringe. Both peptides are stable in BAC water at neutral pH and may share a vial in some research preparations.
- Use a 31G insulin syringe. For a 2 mg/mL concentration, 100 mcg = 0.05 mL = 5 units on a 100-unit insulin syringe.
- Inject subcutaneously, rotating between abdominal sites and posterior arms.
Key Studies & Trial Data
Ipamorelin: novel GH-releasing peptide with clean cortisol profile
The seminal pharmacology paper. Demonstrated that ipamorelin produced a GH pulse comparable to GHRP-6 in pituitary cell cultures and in vivo while showing no measurable elevation in cortisol, prolactin, or ACTH at GH-effective doses — establishing the receptor-selectivity profile that defined the compound.
Raun K, et al. Eur J Endocrinol. 1998;139(5):552–561.
Ipamorelin in the treatment of postoperative ileus
A phase 2b clinical trial investigating ipamorelin as a prokinetic agent for postoperative ileus following bowel resection. While the compound failed to meet its primary endpoint, the trial provided substantial human safety data on multi-day dosing — the largest controlled human dataset on ipamorelin to date.
Beck DE, et al. Dis Colon Rectum. 2014;57(4):498–504.
GHRH + GHRP synergy in healthy adults
Foundational study establishing the GHRH + GHRP synergy principle. Co-administration of a GHRH analog and a GHRP produced a GH pulse 2–4× larger than either alone — the mechanistic basis for the modern CJC-1295 + ipamorelin stack.
Bowers CY, et al. J Clin Endocrinol Metab. 1990;70(4):975–982 (and subsequent work).
Comparisons & Deep Dives
In-depth articles on Peptide Basics that compare Ipamorelin to related compounds and expand on its mechanism and use.
Ipamorelin vs CJC-1295
The two halves of the dominant GH-stack. Mechanism, half-lives, dosing schedules, and why they're almost always run together.
Tesamorelin vs Ipamorelin
Two very different mechanisms — GHRH analog versus ghrelin mimetic — compared head-to-head on data quality, cost, and use cases.
Ipamorelin Side Effects
What the research literature actually shows about tolerability, water retention, glucose effects, and long-term safety markers.
How Growth Hormone Peptides Work
The full GH-secretagogue landscape — where ipamorelin sits versus other GHRPs and GHRH analogs.
Frequently Asked Questions
Where to Source Research-Grade Ipamorelin
Base Peptide
Research-grade ipamorelin (5 mg vial) with batch-specific Certificate of Analysis. The cleanest GHRP in the class — pairs naturally with CJC-1295 for the standard research stack.
Other reputable suppliers known for batch-specific Certificates of Analysis:
Want a deeper, ongoing reference? Peptide Basics maintains a comprehensive resource on ipamorelin alongside calculators, reconstitution guides, and a database of 60+ research peptides.
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