reviewed april 2026|next review october 2026|88 physicians psi has verified|48 published studies
Ipamorelin
Ipamorelin is a synthetic pentapeptide growth hormone secretagogue that selectively activates the ghrelin receptor (GHS-R1a) to stimulate dose-dependent GH release without affecting cortisol, prolactin, or ACTH - the cleanest selectivity profile ever documented for a compound in this class.
Evidence landscape: 48 published studies
48 published items. 3 human studies and 40 animal studies. The cleanest selectivity profile of any GH secretagogue, with almost no published outcomes data.
- 3 Human
- 40 Animal
- 5 Reviews
Not FDA-approved. Placed on the FDA's Category 2 list (a designation that temporarily prevented licensed pharmacies from preparing this compound), meaning licensed pharmacies could not prepare it. It is expected to return to Category 1 (legal for pharmacy preparation) following the February 2026 HHS announcement.
Human pharmacokinetic data confirms selective GH release. A Phase II trial showed post-surgical GI benefit. No controlled human outcomes data for body composition, sleep, or anti-aging.
The most commonly prescribed GH secretagogue in functional medicine. The selectivity advantage over GHRP-6 and hexarelin is confirmed across species.
PSI Assessment
No other growth hormone secretagogue achieves what ipamorelin does pharmacologically: dose-dependent GH release with zero measurable change in cortisol, prolactin, or ACTH. That selectivity profile, confirmed in both animal models and human pharmacokinetic studies, is the reason ipamorelin has become the most commonly prescribed GH secretagogue in functional medicine. The paradox is that one of the most widely used peptides in clinical practice has almost no published outcomes data.
The cleanest selectivity profile of any GH secretagogue ever documented. Zero cortisol, prolactin, or ACTH changes at GH-stimulating doses.
The mechanism is selective ghrelin receptor (GHS-R1a) agonism. Where older GH-releasing peptides like GHRP-6 and hexarelin activate multiple hormonal axes (raising cortisol, prolactin, and appetite alongside GH), ipamorelin activates only the GH axis. The selectivity is documented in the foundational Raun 1998 study and confirmed in Johansen 1999 human pharmacokinetics.
What the evidence supports
Ipamorelin selectively stimulates GH release without affecting cortisol, prolactin, or ACTH in both animal models and limited human pharmacokinetic studies. The selectivity profile is the cleanest ever documented for a GH secretagogue. A Phase II trial showed functional GI benefit post-surgery. The Raun 1998 and Johansen 1999 studies provide cross-species confirmation of the selectivity advantage.
What is not yet established
Whether ipamorelin produces meaningful clinical outcomes for body composition, sleep, bone density, or anti-aging. No controlled human trials exist for these endpoints. How the CJC-1295 plus ipamorelin combination compares to either peptide alone. Long-term safety in humans.
Research Evidence
The findings below cover the confirmed selectivity profile and the gap between clinical adoption and published outcomes data.
Evidence by condition
Evidence dimensions across ipamorelin indications. GH selectivity has cross-species confirmation. All clinical outcome indications lack controlled human data.
| Condition | Mechanism | Animal evidence | Human evidence | Replication |
|---|---|---|---|---|
| GH Stimulation | ||||
| Post-Surgical GI Recovery | ||||
| Body Composition | ||||
| Sleep Quality | ||||
| Bone Health |
Ipamorelin produces dose-dependent GH release without measurable changes in cortisol, prolactin, or ACTH in both animal models (Raun 1998) and human pharmacokinetic studies (Johansen 1999). This selectivity profile is unique among GH secretagogues.
Cross-species replication of the selectivity profile is the strongest aspect of ipamorelin's evidence base. No other GHRP achieves comparable hormonal specificity.
A Phase II trial evaluated ipamorelin for postoperative ileus (delayed gut recovery after abdominal surgery) and showed accelerated return of bowel function.
This is the most rigorous published human data, but the GI motility application is distinct from the typical GH secretagogue use cases in functional medicine. The trial was not replicated.
No controlled human trials have been published for body composition, sleep quality, bone density, or anti-aging endpoints. The CJC-1295 plus ipamorelin combination, the most common clinical protocol, has never been tested in a controlled comparison study.
The gap between clinical adoption and published evidence is wide. Community reports are favorable but do not substitute for controlled trial data.
3 Human|40 Animal|5 Reviews
View all 48 indexed studiesHow Ipamorelin Works
Ipamorelin is a pentapeptide that binds to the growth hormone secretagogue receptor (GHS-R1a) on anterior pituitary somatotrophs, triggering dose-dependent GH release without activating the HPA axis (no cortisol/ACTH increase) or lactotroph cells (no prolactin release). GH release follows the natural pulsatile pattern.
If older GH peptides are like pressing multiple buttons at once, ipamorelin is like having a precise remote that only presses the GH button. Nothing else. That precision is why researchers consider it one of the cleaner GH secretagogues available.
For a more detailed view of the biology, here is what researchers have observed at the molecular level.
Ipamorelin mimics ghrelin, a hunger hormone that also signals the pituitary gland to release growth hormone. What makes ipamorelin unique is its precision: it triggers GH release without the cortisol spikes, ACTH changes, or prolactin elevation caused by other GH secretagogues. This selectivity makes it the cleanest GHRP studied, and is the primary reason it remains of research interest despite the discontinued clinical program.
What is Ipamorelin being studied for?
Researchers are studying Ipamorelin across several health conditions. Each condition below is labeled with the strength of evidence that exists for that specific use, not for Ipamorelin overall. This means a compound can have human studies for one condition but only animal data for another.
GH Stimulation
·Animal StudiesIpamorelin selectively activates the ghrelin receptor (GHS-R1a) to stimulate GH release. Human pharmacokinetic data confirms dose-dependent GH elevation without cortisol or prolactin changes.
Limitations: Selectivity is demonstrated, but clinical significance (whether this translates to better outcomes versus less selective GHRPs) is not established.
Post-Surgical GI Recovery
·Animal StudiesA Phase II trial in patients undergoing abdominal surgery showed ipamorelin accelerated return of bowel function. This is the most rigorous published human data.
Limitations: Single clinical trial with mixed results. The GI motility application is distinct from the typical GH secretagogue use cases. Not replicated.
Body Composition
·PreclinicalCommunity reports suggest improvements in lean mass and fat loss, consistent with GH elevation. No controlled human trials have measured body composition as a primary endpoint.
Limitations: Complete absence of published human body composition data.
Sleep Quality
·PreclinicalGH secretagogues generally improve slow-wave sleep. No published human data specifically evaluates ipamorelin for sleep.
Limitations: Entirely extrapolated from GH class effects. No ipamorelin-specific sleep studies.
Bone Health
·PreclinicalAnimal studies show positive effects on bone density. Published human studies have not evaluated bone endpoints specifically.
Limitations: Only animal data for bone density. Published human studies focused on GH selectivity and GI recovery, not bone endpoints.
Safety and Regulatory Status
FDA Status: Not FDA-approved for any indication. Placed on the FDA's Category 2 list (a designation that temporarily prevented licensed pharmacies from preparing this compound), meaning licensed pharmacies could not prepare it. It is expected to return to Category 1 (legal for pharmacy preparation) following the February 2026 HHS announcement.
Availability: Available through specialty pharmacies where a licensed pharmacist prepares a medicine from ingredients for an individual patient, pending reclassification to legal pharmacy preparation status.
Class context: Selective GH secretagogue (ghrelin receptor agonist). Hexarelin and GHRP-6 are non-selective alternatives. CJC-1295 targets the complementary GHRH receptor.
Well tolerated in the limited human studies published. No significant adverse events reported in the post-surgical trial. The selectivity profile avoids the cortisol and prolactin elevations seen with older GH secretagogues.
Peptide Structure
Technical molecular data for researchers and clinicians.
Questions and Comparisons
Questions the evidence raises for a Ipamorelin discussion.
Comparison and Related Research
Ipamorelin is most often compared with other GH secretagogues. The comparisons below outline how each differs in selectivity, evidence depth, and route of administration.
Head-to-head comparisons
Full research comparisons covering Ipamorelin and another peptide side by side.
Ipamorelin vs CJC-1295
Evidence-based comparison of CJC-1295 and ipamorelin for growth hormone stimulation. Mechanism differences, evidence levels, study findings, and safety profiles analyzed.
View full comparisonIpamorelin vs MK-677
Three-way comparison of MK-677, ipamorelin, and CJC-1295 for growth hormone research. Mechanisms, evidence levels, oral vs. injectable delivery, and safety profiles analyzed.
View full comparisonIpamorelin vs Sermorelin
Sermorelin has a longer clinical history. Ipamorelin is more selective. Evidence-graded comparison for growth hormone optimization, mechanisms, safety, and study data.
View full comparisonIpamorelin vs GHRP-2
GHRP-2 produces a stronger GH pulse but raises cortisol and appetite. Ipamorelin is selective with minimal off-target effects. Evidence-graded comparison.
View full comparisonIpamorelin vs BPC-157
BPC-157 repairs specific tissue damage. Ipamorelin optimizes GH systemically. Evidence-graded comparison of two peptides from different categories.
View full comparisonRelated compounds
Frequently Asked Questions
References
Each citation links to the original study on PubMed, the U.S. National Library of Medicine database.
- 1.The study that established ipamorelin as the first truly selective GH secretagogue. Unlike earlier compounds in this class, ipamorelin stimulated growth hormone release without significantly affecting cortisol or prolactin levels - a selectivity profile that distinguished it from GHRP-6 and GHRP-2.Raun K et al., 1998 in Eur J Endocrinol. View on PubMed
- 2.First pharmacokinetic study of ipamorelin in humans. The modeling work characterized how the peptide is absorbed, distributed, and cleared from the body, and established the dose-response relationship between ipamorelin levels and growth hormone release.Gobburu JV et al., 1999 in Pharm Res. View on PubMed
- 3.Human proof-of-concept trial testing whether ipamorelin could speed recovery of bowel function after colon surgery. The study explored a gastrointestinal application rather than the growth hormone effects that ipamorelin is more commonly associated with.Beck DE et al., 2014 in Int J Colorectal Dis. View on PubMed
- 4.Animal study demonstrating that ipamorelin accelerated the return of normal gut motility after abdominal surgery in rats. The results provided the preclinical rationale for later human trials testing this gastrointestinal recovery application.Venkova K et al., 2009 in J Pharmacol Exp Ther. View on PubMed
Medical Disclaimer
This content is for educational and informational purposes only and does not constitute medical advice. The information presented reflects published research as indexed by PSI and should not be used to make treatment decisions. Always consult a qualified healthcare provider before starting, stopping, or modifying any treatment.