TL;DR: In published research, ipamorelin (a selective GHS-R1a agonist) is studied at microgram-scale amounts per administration, often two to three times daily, with fasted and pre-sleep timing chosen to align with natural GH pulses. Its defining trait is releasing growth hormone without meaningfully raising cortisol, ACTH, or prolactin. All figures below describe laboratory protocols only, not human dosing guidance.
Ipamorelin (Aib-His-D-2-Nal-D-Phe-Lys-NH2) is a synthetic pentapeptide that binds the growth hormone secretagogue receptor type 1a (GHS-R1a), the same receptor targeted by the hormone ghrelin. When researchers reference “ipamorelin dosis” or “ipamorelin dosierung,” they are usually asking how the compound has been administered in animal and early human studies. This article summarises those documented patterns, the timing logic behind them, and how ipamorelin stacks up against the older peptides GHRP-2 and GHRP-6. Nothing here is a therapeutic or human-dosing recommendation; ipamorelin is a research chemical.
How ipamorelin works, in brief
Ipamorelin activates GHS-R1a on pituitary somatotroph cells, triggering a discrete pulse of growth hormone (GH) release. It was described by Raun and colleagues in 1998 as “the first selective growth hormone secretagogue” because, unlike its predecessors, it drove GH output without also stimulating the stress hormones ACTH and cortisol, or prolactin, FSH, LH, and TSH. This selectivity is the single most cited reason researchers reach for it in mechanistic studies: it isolates the GH axis with fewer confounding hormonal signals. For a fuller mechanism overview, see the ipamorelin research profile.
A key pharmacological point is that ipamorelin’s action is pulsatile and short-lived. In healthy male volunteers, Gobburu and colleagues (1999) measured a terminal half-life of roughly two hours, with GH concentrations peaking around 40 minutes after administration and then declining exponentially back toward baseline. That short window is exactly why timing matters in study design.
Dosing patterns seen in research
Because ipamorelin has never been approved for any therapeutic indication, there is no established clinical dose. What exists is a body of preclinical protocols and a handful of early-phase human pharmacology studies. Amounts are consistently reported in micrograms (µg) or as weight-adjusted quantities (µg/kg or mg/kg), not as fixed consumer “doses.”
A few representative research designs:
- Rodent bone-growth work (Johansen et al., 1999): ipamorelin was given subcutaneously at 0, 18, 90, and 450 µg/day, split across three daily administrations for 15 days, producing a dose-dependent increase in longitudinal bone growth rate.
- Rat bone-density work (Svensson et al., 2000): ipamorelin at 0.5 mg/kg per day was delivered continuously via osmotic minipump over 12 weeks, increasing bone mineral content on DXA.
- Human pharmacology (Gobburu et al., 1999): single 15-minute intravenous infusions across escalating rates in healthy men, used to model the concentration–GH-release relationship rather than to treat anything.
- Phase 2 human trial (Beck et al., 2014): intravenous ipamorelin at 0.03 mg/kg twice daily was tested for postoperative ileus; it was well tolerated but did not beat placebo on the primary endpoint.
Two patterns recur across this literature. First, divided administration (commonly two to three times daily) is used to work with GH’s naturally pulsatile secretion rather than against it. Second, the effective quantity is small — because ipamorelin acts as a receptor agonist rather than a hormone replacement, animal studies show responses at microgram-scale amounts, and Raun’s group reported that even at doses more than 200 times the GH-releasing ED50, cortisol and ACTH stayed near baseline. Researchers modelling reconstitution volumes and per-administration amounts often work these figures out with a peptide dosage calculator before setting up an experiment.
Subcutaneous dose split across three daily administrations for 15 days in rats.
Timing considerations: fasted and pre-sleep windows
Timing is a design variable in GH-secretagogue research because two things blunt a GH pulse: circulating somatostatin and elevated blood glucose/insulin.
Fasted state. A meal — particularly one with carbohydrate or fat — raises insulin and free fatty acids, both of which dampen GH release. Many rodent and human secretagogue protocols therefore schedule administration away from feeding, so that the measured GH pulse reflects the peptide’s action rather than a nutrient-suppressed baseline. In practice this means a gap before and after administration in fasted-design studies.
Pre-sleep window. Endogenous GH secretion in mammals is heavily weighted toward the first hours of slow-wave sleep. Aligning a secretagogue pulse with this natural nocturnal surge is a common rationale in study design, since it layers an evoked pulse onto the largest physiological one. This is why “pre-sleep” appears so often in ipamorelin research discussions.
Neither point should be read as a usage instruction. They simply explain why published protocols cluster administrations around fasted and nocturnal windows: those are the conditions under which a GH-secretagogue signal is cleanest to measure.
Ipamorelin vs GHRP-2 vs GHRP-6
Ipamorelin belongs to the same GHS-R1a agonist family as the older peptides GHRP-2 and GHRP-6, but the three differ meaningfully in selectivity, appetite effects, and potency. The table below summarises the comparative picture reported in the primary literature (chiefly Raun et al., 1998, and subsequent rodent work). All entries are research characterisations, not endorsements.
| Characteristic | Ipamorelin | GHRP-2 | GHRP-6 |
|---|---|---|---|
| Receptor | GHS-R1a (ghrelin receptor) | GHS-R1a | GHS-R1a |
| GH-release selectivity | High — minimal ACTH/cortisol/prolactin | Moderate — dose-dependent ACTH/cortisol rise | Moderate — notable ACTH/cortisol rise |
| Prolactin effect | Minimal | Highest of the three | Intermediate |
| Appetite stimulation | Minimal in reported studies | Mild to moderate | Pronounced (strong ghrelin-like hunger) |
| Relative GH potency | High per-microgram in animal models | Highest raw GH output reported | Lower than GHRP-2 |
| Research reputation | ”Cleanest” / most selective | Potent but less selective | Classic ghrelin-mimetic, appetite research |
The headline takeaway from Raun and colleagues is that GHRP-6 and GHRP-2 both raised plasma ACTH and cortisol, whereas ipamorelin did not exceed the levels seen with GHRH alone. Ipamorelin also lacks the intense appetite stimulation associated with GHRP-6, which makes it attractive when investigators want a GH signal uncontaminated by feeding behaviour. GHRP-2, by contrast, is often noted for the highest raw GH output but carries more prolactin and cortisol co-secretion. You can review each compound’s individual profile on the GHRP-2 reference page and the GHRP-6 reference page.
What the research shows — and its limits
The honest framing is that most ipamorelin evidence is preclinical. The bone-growth (Johansen 1999) and bone-mineral-content (Svensson 2000) findings come from rats. The selectivity data (Raun 1998) combine in vitro, animal, and limited human pharmacology. Human work exists but is thin: Gobburu’s 1999 study characterised pharmacokinetics and GH response in healthy men, and Beck’s 2014 Phase 2 trial tested ipamorelin for postoperative ileus in 100-plus surgical patients — where it was safe but failed its primary efficacy endpoint, after which clinical development was discontinued.
That trajectory matters. Robust GH-releasing activity in humans is well documented, but ipamorelin has no approved indication, and the one substantial efficacy trial did not succeed. Reviews of GH secretagogues (for example, Sinha et al., 2020) continue to describe these peptides as investigational, with long-term outcome and safety data lacking. Extrapolating rodent bone or growth findings to any human context is not supported by the current evidence base. This is why every figure in this article is presented as a research parameter, not guidance.
Frequently Asked Questions
What is the typical ipamorelin dosis in studies?
There is no approved clinical dose. Research protocols report weight-adjusted amounts — for example, 18–450 µg/day in rodent bone studies (split across three daily administrations) or 0.03 mg/kg twice daily intravenously in one human trial. These describe experimental design only, not a recommended human dose.
Why is fasted timing used for ipamorelin research?
Food, especially carbohydrate and fat, raises insulin and free fatty acids, both of which suppress growth hormone release. Studies schedule administration away from meals so the measured GH pulse reflects the peptide’s action rather than a nutrient-blunted baseline. It is a measurement-quality choice, not a usage instruction.
Is ipamorelin better than GHRP-2 or GHRP-6?
“Better” depends on the research question. Ipamorelin is the most selective, releasing GH with minimal cortisol, prolactin, and appetite effects. GHRP-2 produces high raw GH output but more prolactin and cortisol; GHRP-6 strongly stimulates appetite. Each suits different experimental aims rather than being universally superior.
Does ipamorelin increase cortisol or prolactin?
In the foundational research by Raun and colleagues (1998), ipamorelin did not raise ACTH, cortisol, or prolactin above levels seen with GHRH alone — even at very high doses. This clean selectivity is its defining laboratory characteristic and the main reason it is studied over older GHRPs.
How long does ipamorelin stay active?
In healthy male volunteers, ipamorelin showed a terminal half-life of about two hours, with growth hormone peaking roughly 40 minutes after administration before declining back toward baseline. Its effect is a single, short, pulsatile GH release rather than sustained elevation, which shapes how divided-administration protocols are designed.
Can ipamorelin research findings be applied to humans?
Not directly. Most data — bone growth, bone density, body-weight effects — come from rodents. The limited human work is early-phase pharmacology plus one Phase 2 trial that missed its endpoint. Ipamorelin has no approved indication, so animal results should not be treated as human-outcome evidence.
References
- Raun K, Hansen BS, Johansen NL, et al. Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology. 1998;139(5):552–561.
- Gobburu JV, Agersø H, Jusko WJ, Ynddal L. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharmaceutical Research. 1999;16(9):1412–1416.
- Johansen PB, Nowak J, Skjaerbaek C, et al. Ipamorelin, a new growth-hormone-releasing peptide, induces longitudinal bone growth in rats. Growth Hormone & IGF Research. 1999;9(2):106–113.
- Svensson J, Lall S, Dickson SL, et al. The GH secretagogues ipamorelin and GH-releasing peptide-6 increase bone mineral content in adult female rats. Journal of Endocrinology. 2000;165(3):569–577.
- Beck DE, Sweeney WB, McCarter MD; Ipamorelin 201 Study Group. Prospective, randomized, controlled, proof-of-concept study of the ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. International Journal of Colorectal Disease. 2014;29(12):1527–1534.
- Sinha DK, Balasubramanian A, Tatem AJ, et al. Beyond the androgen receptor: the role of growth hormone secretagogues in the modern management of body composition in hypogonadal males. Translational Andrology and Urology. 2020;9(Suppl 2):S149–S159.
Research-use-only disclaimer: This article is an educational reference for laboratory and research contexts. Ipamorelin is not approved for human or veterinary therapeutic use, and nothing here constitutes medical advice, a dosing recommendation, or an endorsement of use in humans. All quantities and timing described reflect published experimental protocols only. Handle research materials in accordance with applicable EU regulations and institutional safety requirements.