What Is Ipamorelin? A Research Guide to the Selective GHRP
Ipamorelin holds a distinctive position in the growth hormone research space: it was the first growth hormone-releasing peptide (GHRP) demonstrated to be truly selective. While earlier GHRPs like GHRP-6 and GHRP-2 effectively stimulated GH release, they also triggered unwanted increases in cortisol, prolactin, and appetite. Ipamorelin solved this problem, and that selectivity is the central reason for its popularity in research protocols.
This guide explains what ipamorelin is, how it works, what the published research shows, and how to compare vendor prices.
What Is Ipamorelin?
Ipamorelin is a synthetic pentapeptide -- five amino acids -- that acts as a growth hormone secretagogue (GHS). It was first characterized in a 1998 paper in the European Journal of Endocrinology (PMID: 9849822) that established its selectivity profile.
Like other GHRPs, ipamorelin binds to the ghrelin receptor (GHS-R1a) on pituitary somatotroph cells, triggering the release of growth hormone. What distinguishes it is what it does not do: at GH-stimulating doses, ipamorelin does not significantly increase cortisol, ACTH, prolactin, or FSH levels. This selectivity means it stimulates GH release without the hormonal side effects that complicated earlier GHRPs.
Ipamorelin is not FDA-approved and is sold as a research chemical.
View the full ipamorelin research profile and compare vendor prices on PeptidePrices.
How Does Ipamorelin Work?
Ipamorelin works through the ghrelin/GHS receptor pathway, which is distinct from (and complementary to) the GHRH receptor pathway used by compounds like CJC-1295 and tesamorelin.
Ghrelin receptor activation. The ghrelin receptor (GHS-R1a) is expressed on pituitary somatotroph cells. When ipamorelin binds this receptor, it triggers GH release through a phospholipase C / inositol phosphate signaling cascade. This is a different intracellular mechanism than GHRH receptor activation, which is why the two pathways are synergistic.
Pulsatile GH release. Ipamorelin stimulates GH release in discrete pulses rather than sustained elevation. A pharmacokinetic study published in the British Journal of Pharmacology (1999, PMID: 10496658) characterized the human dose-response: single IV doses of 1 to 10 mcg/kg produced dose-proportional GH peaks with rapid clearance. This pulsatile pattern closely mimics natural GH secretion.
Selectivity mechanism. The selectivity of ipamorelin appears to stem from its specific receptor binding characteristics. Unlike GHRP-6, which activates multiple downstream pathways including those that stimulate cortisol and appetite, ipamorelin's binding profile produces a cleaner signal that triggers GH release without activating the broader endocrine cascade.
Preservation of feedback regulation. Because ipamorelin stimulates endogenous GH production from the pituitary -- rather than introducing exogenous GH -- the natural IGF-1 negative feedback loop remains functional. The body retains its ability to self-regulate GH levels, which is a meaningful distinction from injectable HGH.
What Does the Research Say?
Selectivity confirmation. The foundational 1998 European Journal of Endocrinology study demonstrated that ipamorelin produced robust, dose-dependent GH release in rats without affecting ACTH, cortisol, prolactin, or FSH at any dose tested -- a profile no previous GHRP had achieved.
Human pharmacokinetics. The 1999 British Journal of Pharmacology study confirmed dose-proportional GH responses in healthy human volunteers, with peak GH levels occurring within 40 minutes of administration and returning to baseline within 3 hours.
Bone growth without side effects. A study in GH and IGF Research (2001, PMID: 10373343) found that ipamorelin stimulated longitudinal bone growth in rats at rates comparable to GH itself, without the cortisol and prolactin elevations seen with other GHRPs. This finding highlighted ipamorelin's potential relevance to musculoskeletal research.
Post-operative GI recovery. A Phase 2 clinical trial (Journal of Gastrointestinal Surgery, 2014, PMID: 25331030) evaluated ipamorelin for post-operative ileus -- the temporary paralysis of gut motility that occurs after abdominal surgery. The trial reported that ipamorelin accelerated GI motility recovery with a favorable benefit-risk profile. This is one of the few clinical indications where ipamorelin has been formally evaluated in a controlled human trial.
GH secretagogue reviews. A 2018 review in Translational Andrology and Urology (PMID: 30186644) positioned ipamorelin as the preferred GHRP for research protocols due to its selectivity, tolerability, and synergistic pairing potential with GHRH analogues.
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Ipamorelin Safety Profile
PeptidePrices assigns ipamorelin a safety rating of 7 out of 10. It is the most selective GHRP available, with human pharmacokinetic data and a Phase 2 clinical trial demonstrating good tolerability. The absence of cortisol and prolactin stimulation is a significant safety advantage over GHRP-6 and GHRP-2.
Reported side effects in the literature are mild and typically include transient headache, flushing, and light-headedness. No serious adverse events have been reported in published clinical studies. The compound is not FDA-approved, and long-term human safety data from large-scale trials is not available.
Ipamorelin vs. Other GHRPs
| Compound | GH Release | Cortisol | Prolactin | Appetite | Selectivity |
|---|---|---|---|---|---|
| Ipamorelin | Strong | No increase | No increase | Minimal | Highest |
| GHRP-2 | Very strong | Moderate increase | Moderate increase | Moderate | Moderate |
| GHRP-6 | Strong | Moderate increase | Moderate increase | Strong increase | Lowest |
| Hexarelin | Very strong | Significant increase | Significant increase | Moderate | Low |
Ipamorelin's selectivity makes it the preferred GHRP for research protocols where hormonal side effects are a concern. GHRP-6 may be preferred in research contexts where appetite stimulation (e.g., cachexia models) is desirable. GHRP-2 and hexarelin produce stronger GH peaks but with more hormonal disruption.
The CJC-1295 + ipamorelin combination. The most frequently discussed research pairing in the GH space combines CJC-1295 No DAC (a GHRH analogue) with ipamorelin (a GHRP). The rationale is pharmacological synergy: GHRH increases the amplitude of GH pulses while GHRP increases the frequency. Together, they produce significantly more GH release than either compound alone, while maintaining ipamorelin's clean selectivity profile.
Dosing in Research Settings
The following is for informational purposes only and does not constitute medical advice.
In the published human PK study, ipamorelin was administered intravenously at 1 to 10 mcg/kg. In research protocol contexts, subcutaneous injection is the more commonly discussed route, typically at doses of 200-300 mcg per administration, 2-3 times daily.
When paired with CJC-1295 No DAC, both compounds are typically administered simultaneously via subcutaneous injection. No standardized clinical protocols exist for this combination, and all dosing information available online is derived from published studies and researcher-reported protocols.
Comparing Ipamorelin Prices
Ipamorelin is one of the more widely stocked research peptides, available from most major vendors. Prices vary substantially -- sometimes by 30% or more for the same quantity -- so comparison shopping is worth the effort.
PeptidePrices normalizes all ipamorelin pricing to a per-milligram basis across 19+ tracked vendors.
See the live ipamorelin price comparison across all vendors.
The AI Stack Builder can help you explore GH-axis research protocols, including the popular CJC-1295 + ipamorelin pairing.
Wrapping Up
Ipamorelin is the gold standard for selective GH secretagogue research -- it produces robust, dose-dependent, pulsatile growth hormone release without the cortisol, prolactin, and appetite side effects that limit other GHRPs. Backed by human PK data, a Phase 2 clinical trial, and extensive preclinical characterization, it has one of the stronger evidence bases in the research peptide category.
If you are researching ipamorelin, review the published selectivity data, consider how it fits into a broader GH-axis protocol, and compare vendor prices before purchasing.
Compare ipamorelin prices across all vendors at PeptidePrices -- research smarter, spend less.
For research purposes only. Not for human consumption. Not medical advice. Always consult a qualified healthcare provider before making any health or supplementation decisions.
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