Ipamorelin
Also known as: Ipamorelin Acetate, NNC 26-0161, IPAM
What Is Ipamorelin?
Ipamorelin is a synthetic pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2) that functions as a selective growth hormone secretagogue (GHS) by mimicking ghrelin at the GHS receptor (GHSR-1a). Molecular weight: ~711.9 Da. CAS: 170851-70-4. Originally developed by Novo Nordisk as NNC 26-0161.
What makes ipamorelin notable within the ghrelin mimetic class is its selectivity. Unlike older growth hormone releasing peptides (GHRP-6, GHRP-2, hexarelin), ipamorelin stimulates GH release with minimal effects on cortisol, prolactin, and ACTH at standard doses. This selectivity profile was established in animal studies and small human trials and is the primary reason ipamorelin became the preferred GHRP in clinical and biohacking contexts.
How It Works
Ipamorelin activates the growth hormone secretagogue receptor (GHSR-1a), the same receptor targeted by the endogenous hormone ghrelin. This receptor is expressed on anterior pituitary somatotrophs and, when activated, amplifies GH release through a pathway complementary to — but distinct from — GHRH signaling.
The key pharmacological distinction:
- GHRH (sermorelin, CJC-1295): Tells the pituitary to produce and release GH — acts as the primary signal
- Ghrelin/GHS-R agonists (ipamorelin): Amplifies the GH release response and partially suppresses somatostatin’s inhibitory tone — acts as the amplifier
This is why ipamorelin is almost always discussed in combination with a GHRH analogue (typically CJC-1295 without DAC). Activating both pathways simultaneously produces synergistic GH output greater than either pathway alone. Think of it as pressing the gas pedal (GHRH) while also releasing the brake (ghrelin signaling reducing somatostatin tone).
Selectivity explained: Older GHRPs like GHRP-6 and GHRP-2 are “dirty” agonists — they significantly raise cortisol and prolactin alongside GH. GHRP-6 is also notorious for inducing intense hunger (ghrelin is the “hunger hormone”). Ipamorelin, in preclinical and early clinical data, demonstrated GH stimulation at doses that did not meaningfully elevate cortisol or prolactin. It also produces less appetite stimulation than GHRP-6, though some users still report increased hunger.
What the Research Actually Shows
The Clinical Data
Ipamorelin has more published human pharmacological data than CJC-1295 (without DAC) but less than sermorelin:
Raun K et al. (Eur J Endocrinol, 1998;139(5):552–561): The foundational study. Demonstrated that ipamorelin is a potent and selective GH secretagogue in swine, with dose-dependent GH release and no significant effects on ACTH, cortisol, prolactin, FSH, LH, or TSH. Importantly, this selectivity was maintained even at high doses — unlike GHRP-6 and GHRP-2, which lose selectivity at higher concentrations.
Phase I/II clinical data (Novo Nordisk internal program): Ipamorelin was evaluated in several clinical contexts, most notably for post-operative ileus (delayed bowel recovery after abdominal surgery). These trials demonstrated that ipamorelin could stimulate GH release in humans and had a favorable safety profile. However, the clinical program was ultimately discontinued — the Phase III trial for post-operative ileus failed to meet its primary endpoint.
Goebel-Stengel M et al. (Neurogastroenterol Motil, 2014;26(2):264–272): Confirmed ghrelin receptor-mediated effects on GI motility in animal models.
Sigalos JT and Pastuszak AW (Sex Med Rev, 2018;6(1):45–53): Comprehensive review of GH secretagogue safety and efficacy. Noted ipamorelin’s favorable selectivity profile and relatively limited clinical data. Concluded that while GHS show promise, their “current data on clinical efficacy largely remain lacking.”
What’s Missing
- No FDA-approved indication — ever. Unlike sermorelin, ipamorelin has never been FDA-approved for any use.
- No completed Phase III trial — the post-operative ileus program failed and was abandoned.
- No published body composition trial — the claim that ipamorelin builds muscle or burns fat has never been tested in a controlled human study.
- No published data on the ipamorelin + CJC-1295 combination — the grey market’s most popular GH secretagogue protocol has zero published evidence.
- No long-term safety data — chronic human use data does not exist in published literature.
- No published comparison with sermorelin — the claim that ipamorelin is “better” has no comparative evidence.
Ipamorelin has established pharmacology (selective GHSR-1a agonist with favorable cortisol/prolactin profile) based on animal studies and limited human Phase I/II data. The clinical program was abandoned after Phase III failure. No published evidence supports the specific use cases marketed to consumers (muscle growth, fat loss, anti-aging, recovery). Evidence level: Limited Human.
The Selectivity Advantage — In Context
Ipamorelin’s selectivity profile is often presented as proof of safety. This deserves nuance:
What selectivity means: At therapeutic doses, ipamorelin stimulates GH release without meaningfully elevating cortisol or prolactin. This is a real pharmacological advantage over GHRP-6 and GHRP-2, where cortisol and prolactin elevation can produce unwanted effects (cortisol -> stress response and catabolic effects; prolactin -> potential for gynecomastia and suppressed libido in men).
What selectivity doesn’t mean: Selectivity at the receptor level does not guarantee overall clinical safety. GH itself has downstream effects — IGF-1 elevation, insulin resistance, fluid retention — that occur regardless of whether the GH was stimulated “selectively” or not. A clean receptor profile is a pharmacological advantage, not a safety guarantee.
Safety Profile
From available clinical data: Generally well-tolerated in published trials. Reported side effects include injection site reactions, transient headache, and occasional nausea. The selectivity profile means less cortisol disruption and less prolactin elevation than GHRP-6/GHRP-2.
The “GH flush”: Many users report a warm sensation, facial flushing, and tingling in hands/feet 5–15 minutes after injection. This is commonly cited in the community as confirmation that the product is working. While likely related to GH release and subsequent vasodilation, it is not a validated biomarker of efficacy.
Unknowns: No long-term safety data. No data on chronic GH/IGF-1 elevation from sustained ipamorelin use. No data on effects in populations with insulin resistance, metabolic syndrome, or cancer history. No safety data for the ipamorelin + CJC-1295 combination at any dose.
Legal and Regulatory Status
FDA: Category 2 — ipamorelin presents “significant safety risks” and cannot be legally compounded. The PCAC explicitly voted against including ipamorelin on the compounding bulks list in December 2024. Ipamorelin has never been FDA-approved for any indication. The Tailor Made Compounding federal conviction involved distribution of ipamorelin.
WADA: Prohibited under S2.2.4 (Growth Hormone Releasing Factors) as a GH secretagogue. Banned at all times, in and out of competition.
State enforcement: Ohio Board of Pharmacy has issued summary suspension orders against clinics possessing ipamorelin alongside BPC-157 and AOD-9604. Four medical spa licenses were suspended.
Grey-market availability: Remains widely sold as a research chemical, typically at $25–50 per 5mg vial. Often bundled with CJC-1295 as a “combo” or sold pre-mixed.
Common Vendor Claims vs. Reality
| What vendors say | What the evidence shows |
|---|---|
| ”Selective GH release with no cortisol spike” | Selectivity is established in animal studies and limited human data — this is the strongest evidence-backed claim |
| ”Builds lean muscle and burns fat” | No human body composition trial has been published |
| ”Best combined with CJC-1295” | Mechanistically sound but never studied in any published human trial |
| ”Clinically proven” | Failed its Phase III trial; clinical program abandoned |
| ”Safest GHRP available” | Selective does not equal safe. Better receptor profile than GHRP-6, but no long-term human safety data |
| ”Can be prescribed by your doctor” | Can be prescribed off-label but cannot be legally compounded since January 2025 (Category 2) |
The Bottom Line
Ipamorelin’s story is one of genuine pharmacological promise that was never clinically validated. Its selectivity profile — stimulating GH without cortisol and prolactin spikes — is a real advantage over older GHRPs, and this is supported by published data. But the clinical program that could have turned this pharmacological promise into proven therapy was abandoned after a Phase III failure.
The grey market adopted ipamorelin and paired it with CJC-1295 to create the most popular GH secretagogue protocol in the biohacking community. This stack is mechanistically rational. It has never been studied in any published trial. And as of January 2025, both components are Category 2 prohibited — meaning the legal pathway that once existed through compounding pharmacies is closed.
For anyone weighing ipamorelin against sermorelin: sermorelin has prior FDA approval, Category 1 status, and can be legally obtained through compounding pharmacies with a prescription. Ipamorelin has a better selectivity profile but no FDA approval history, Category 2 prohibition, and must be sourced from the grey market. The pharmacological argument for ipamorelin is reasonable. The legal and evidence argument strongly favors sermorelin.
Raun K et al., Eur J Endocrinol, 1998;139(5):552–561; Sigalos JT & Pastuszak AW, Sex Med Rev, 2018;6(1):45–53; Sinha DK et al., World J Mens Health, 2020;38(2):151–164; Goebel-Stengel M et al., Neurogastroenterol Motil, 2014;26(2):264–272; FDA PCAC proceedings, December 2024; Ohio Board of Pharmacy enforcement actions; WADA 2026 Prohibited List.
This profile will be updated as new research becomes available. Last reviewed: February 25, 2026.