
Growth hormone release
In a dose-escalation study of eight healthy men per dose level, ipamorelin released growth hormone at every dose tested, in a predictable, dose-related way.2

Aib-His-D-2Nal-D-Phe-Lys-NH2
Ipamorelin was described in 1998, a year before scientists announced ghrelin, the stomach hormone it imitates. In pigs, it released growth hormone without the stress-hormone surge its older cousins caused.
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Ipamorelin is a five-amino-acid peptide that mimics ghrelin, binding a receptor on the pituitary gland to trigger a short pulse of the body’s own growth hormone. It was designed to do this without raising stress hormones such as cortisol. It is studied for growth hormone release and, in one trial, gut recovery after surgery, with only early human data so far.
Medically reviewed by Robert Lufkin, MD (opens in a new tab)
Chief Medical Officer, Vitals Vault · Updated · 11 sources
Ipamorelin asks the pituitary to release growth hormone instead of supplying it.
Tests with blocking drugs showed it releases growth hormone the way ghrelin, a hunger hormone, does.1
In pigs, older peptides of this class raised stress hormones. Ipamorelin did not, even at over 200 times the effective dose.1
In healthy men, an infusion caused one burst of growth hormone that peaked in about 40 minutes and then faded.24
Human evidence for ipamorelin is thin: hormone levels in volunteers and one surgery trial that did not show a benefit. The rest is animal work.
In rat pituitary cells, it released growth hormone the way GHRP-6 does.1
Shows a mechanism
In pigs, it raised growth hormone without raising stress hormones. In adult rats, bone growth rose with the dose.17
Shows an effect in a body
In healthy men it released growth hormone in a dose-related way. A 117-patient surgery trial found no significant benefit over placebo.23
Shows it works in people
Ipamorelin has a clean pharmacology story and a thin clinical one. Animal work showed selectivity, a volunteer study mapped how it behaves in the body, and a phase 2 trial in surgical patients found it was well tolerated without proving a benefit. None of the studies cited here is a large trial of ipamorelin for body composition, sleep or aging.123
The full guide to Ipamorelin
Ipamorelin was built to fit a lock that, at the time, had no known owner. In the years before ipamorelin, chemists made small synthetic molecules that reliably pushed the pituitary gland to release growth hormone. They worked, yet nobody knew which natural hormone they were imitating. Drug hunters had cut a key before anyone had seen the door it was meant for.
In 1996, a team at Merck cloned the receptor these molecules bind, on the pituitary and in the hypothalamus of pigs and people. They wrote that the drugs seemed to mimic a hormone nobody had discovered yet. Three years later, Japanese researchers found it in the stomach: a 28-amino-acid peptide they named ghrelin, from ghre, a Proto-Indo-European root meaning to grow.
Ipamorelin landed in the middle of that story. In 1998, a year before ghrelin had a name, researchers at Novo Nordisk described it in the European Journal of Endocrinology as the first selective growth hormone secretagogue. It came out of a large chemistry program that trimmed the central two amino acids from an older compound called GHRP-1, leaving a chain of five.
That word, selective, is what ipamorelin’s reputation still rests on, far more than its slim clinical record. To see why selectivity mattered so much to the people who made it, you need to know what the older molecules in this family did besides release growth hormone.561
Your pituitary takes instructions on growth hormone from more than one direction. Growth hormone releasing hormone, or GHRH, from the hypothalamus pushes release. Somatostatin holds it back. Ghrelin adds a third input through its own receptor, the growth hormone secretagogue receptor. Ipamorelin plugs into that third input, so it works one step upstream of growth hormone and never supplies the hormone itself.
The Novo Nordisk team proved the route with blocking drugs. When they used antagonists for each pathway, ipamorelin behaved like GHRP-6 and released growth hormone through a GHRP-type receptor, the family ghrelin turned out to own. In rat pituitary cells and in live rats and pigs, its potency and peak effect were close to GHRP-6.
In people, the effect is a single wave. In 1999, healthy men received ipamorelin infusions at five dose levels, eight men per level. Each infusion produced one episode of growth hormone release that peaked at about 40 minutes and then declined to negligible levels. Ipamorelin itself had a half-life of about 2 hours, and the response scaled with the dose.
Because the pituitary is releasing its own stores, the body’s normal brakes stay on. Reviews of the whole secretagogue class describe pulsatile release that remains subject to negative feedback, which can prevent the very high growth hormone levels that injected hormone can produce. Reviewers count that preserved feedback among the class’s potential advantages, though it is a brake, not a guarantee.124
The experiment that defined ipamorelin was run in conscious pigs. There, the older peptides GHRP-6 and GHRP-2 raised growth hormone and also pushed up ACTH and cortisol, the body’s main stress hormones. Ipamorelin raised growth hormone alone. Its effect on ACTH and cortisol was no different from that of GHRH, even at doses more than 200 times higher than the dose needed for half its growth hormone effect.
The authors used an unusual phrase for a journal paper. They called the result very surprising. None of the peptides they tested moved FSH, LH, prolactin or TSH, so the cortisol finding was the one thing that separated ipamorelin from its relatives, and it gave it a selectivity for growth hormone similar to GHRH itself.
Why care about cortisol? People interested in growth hormone usually want what it does for muscle, fat and repair. Cortisol, over time, tends to pull the other way: it breaks down protein and raises blood sugar. A peptide that asks for growth hormone without sounding the stress alarm is, in principle, a cleaner request.
One caution keeps this honest. The cortisol data that built ipamorelin’s reputation came from swine. The human studies cited on this page measured growth hormone and gut recovery, and none of them reports a head-to-head cortisol comparison in people. Without human cortisol data in these sources, selectivity in people remains an inference.1
Ghrelin is famous for hunger, and it also moves the gut. That made ipamorelin a candidate for postoperative ileus, the frustrating days after abdominal surgery when the bowel stops moving, patients cannot eat, and hospital stays stretch out. It is also the use behind the randomized human efficacy trial cited here.
The animal work looked encouraging. In a 2009 rat model of postoperative ileus, a single dose of ipamorelin shortened the time to the first bowel movement. Repeated dosing over two days went further, raising stool output, food intake and body weight gain compared with saline. The authors suggested it might ease symptoms in surgical patients.
Then came people. A phase 2 trial enrolled 117 adults having small or large bowel resection, with 114 included in the analysis. They received intravenous ipamorelin or placebo for up to seven days in hospital. Median time to a first tolerated solid meal was 25.3 hours on ipamorelin and 32.6 hours on placebo, a gap that did not reach statistical significance.
Adverse events were common in both groups, as you would expect after major surgery, and slightly less frequent on ipamorelin (87.5% versus 94.8%). The authors concluded it was well tolerated and showed no significant difference on the main or secondary outcomes. They also noted the study was small and mixed many underlying conditions, which leaves the question open more than closed.83
Most people searching for ipamorelin want to know about muscle, fat, sleep and recovery. This is where the gap between reputation and record is widest, so it helps to separate what was measured in animals, what was measured in people, and what is borrowed from the wider class of growth hormone secretagogues.
Novo Nordisk’s own animal work came first. In adult female rats given ipamorelin for 15 days, the growth rate of the shin bone rose with dose, from 42 micrometers a day on vehicle to 52 at the highest dose, alongside a clear gain in body weight. Oddly, total IGF-1 did not change, nor did blood markers of bone building and breakdown.
In people, the evidence comes from reviews of the secretagogue family as a whole. The 2018 Sexual Medicine Reviews analysis lists possible effects including better lean mass in wasting and obesity, lower bone turnover, more fat-free mass and better sleep. The same authors stress that few long-term, rigorously controlled studies exist for any of these drugs.
Put together, ipamorelin reliably releases growth hormone in people, and growth hormone has well-known effects on body composition. None of the studies cited here shows that ipamorelin itself builds muscle, burns fat or improves sleep in adults. Those claims borrow from the hormone and from the class.74
Buried in the 1999 volunteer study is a finding that deserves more attention than it gets. The researchers modeled two things separately: how the body handles ipamorelin, and how strongly the pituitary answers it. The variation between people was larger for the answer than for the drug handling.
Put simply, how the men’s bodies handled ipamorelin varied less than how much growth hormone their pituitaries released in response. The signal arrived at the door in roughly similar shape. The size of the reply varied more.
That fits what endocrinologists already know about growth hormone. The pituitary’s output depends on its surroundings: deep sleep, body fat, insulin, age and the balance of GHRH and somatostatin. A secretagogue can only amplify a system that is ready to answer. That reading is a hypothesis, since the study did not set out to test it.
The practical lesson is that the context around a growth hormone secretagogue may matter as much as the molecule. Two people on the same prescription can have very different results. The study did not identify what drives those differences, and no test predicts an individual’s response, though sleep, body fat and metabolic health are reasonable places for a clinician to start looking.24
Ipamorelin is often discussed as one member of a crowded family, so it helps to place it. GHRP-6 and GHRP-2 act on the same ghrelin-type receptor. In the 1998 pig work, GHRP-2 was more potent but produced a smaller peak, GHRP-6 matched ipamorelin closely, and both of the older peptides raised ACTH and cortisol where ipamorelin did not.
CJC-1295 sits on the other arm of the system. It is a modified form of GHRH and acts on the GHRH receptor, the same pituitary cells reached by a different door. Sermorelin and tesamorelin are also GHRH analogs. MK-677 is an oral, non-peptide molecule that, like ipamorelin, acts at the ghrelin receptor.
That is why ipamorelin and CJC-1295 are so often paired online. The logic is physiological: push from the GHRH side, add the ghrelin input, and the pituitary may answer more strongly than to either alone. None of the studies cited on this page tested that pairing, so treat the combination as a hypothesis.14
The best human safety data come from the surgical trial, where intravenous ipamorelin for up to seven days was well tolerated and adverse events were no more common than on placebo. That is reassuring for a short hospital course. It says little about months of use at home.
Reviews of the secretagogue class add one consistent concern. Growth hormone lowers insulin sensitivity, so blood glucose can rise. The same reviewers note that long-term evidence is limited and call for more study of cancer incidence and mortality. Growth hormone and IGF-1 encourage cell growth, which is why a cancer history deserves a careful conversation.
FDA’s compounding safety page goes further. It cites the risk of the body forming antibodies to the peptide, the difficulty of characterizing a molecule built from unnatural amino acids, and a report of serious adverse events, including death, in a study that gave ipamorelin intravenously for gut motility. Those concerns are part of why FDA has not opened compounding for it.
The practical risk for most people is the vial. Products sold online as research chemicals are not made for human use, and peptide purity depends on the facility. People with diabetes or prediabetes, a cancer history, heart or kidney disease, or a pregnancy should talk to a clinician first, and tested athletes should assume it is banned.349
Because the clearest known downside of raising growth hormone is on blood sugar, the labs most relevant to that concern are metabolic. Fasting glucose is the simplest snapshot. HbA1c shows your average blood sugar over roughly three months, so it catches a slow drift that a single morning reading can miss.
Fasting insulin adds context. Higher insulin with a normal glucose can be consistent with the pancreas working harder to keep sugar in range as insulin sensitivity falls, though it is not diagnostic on its own and needs a clinician to interpret. The secretagogue reviews flag higher blood glucose tied to reduced insulin sensitivity, which is the concern these markers speak to.
eGFR, the estimated filtration rate of your kidneys, adds a general baseline of kidney function. None of this is a validated ipamorelin monitoring panel; it is baseline context that a clinician reads alongside your history. Vitals Vault starts peptide care with a blood panel, a licensed clinician reviews it with your history, and a retest shows which way you are moving.4
Ipamorelin is not an approved drug. On September 29, 2023, FDA placed ipamorelin acetate in category 2 of bulk substances under its 503B interim policy, the group it flags for significant safety risks. It is not one of the six peptides covered by FDA’s October 2026 enforcement-discretion policy for 503A pharmacies.
Sport has its own rule. The World Anti-Doping Agency prohibits growth hormone secretagogues, including ghrelin mimetics like ipamorelin, at all times, so anyone in tested competition should treat it as banned.91011
Ipamorelin is an elegant piece of chemistry. It asks the pituitary for a single, short pulse of growth hormone, and in pigs it did so without the stress-hormone surge its older cousins caused. In people, it releases growth hormone predictably. The randomized efficacy trial cited here, for gut recovery after surgery, did not beat placebo, and no study cited here shows the body composition results people hope for.
If you are curious about it, start with what shapes growth hormone release anyway: sleep, visceral fat, insulin and training. A baseline of glucose, HbA1c and insulin gives a clinician metabolic context. It cannot tell you whether your growth hormone is low; that takes a targeted endocrine evaluation, usually a stimulation test.123
In the volunteer study, growth hormone peaked about 40 minutes after an infusion and faded within hours, and ipamorelin’s own half-life was about 2 hours. Any felt effect therefore depends on what that repeated pulse does downstream, which in the wider secretagogue literature takes weeks to show in body composition, if it shows at all.
A responsible start is a health history, a baseline of glucose, HbA1c and insulin, and a clinician’s view on whether a secretagogue makes sense for you. A retest of the same markers is how you see whether your blood sugar is holding steady.24
Raun et al., 19981
Laboratory and animal pharmacology · Rat pituitary cells, rats and pigs
Released growth hormone like GHRP-6 without raising ACTH or cortisol, even at over 200 times the half-effective dose
Limits: Animal data; cortisol not compared in people
Johansen et al., 19997
Animal study, 15 days · Adult female rats
Faster longitudinal bone growth and body weight gain, rising with dose
Limits: Rats; IGF-1 and bone markers did not change
Gobburu et al., 19992
Dose-escalation study · Healthy men, 8 per dose level, 5 levels
One growth hormone pulse peaking near 40 minutes; half-life about 2 hours
Limits: Single infusions; no outcomes beyond hormone levels
Venkova et al., 20098
Animal model of postoperative ileus · Rats after abdominal surgery
Faster first bowel movement; repeated dosing raised food intake and weight gain
Limits: Rodent model
Beck et al., 20143
Randomized, double-blind, placebo-controlled phase 2 · 117 adults after bowel resection (114 analyzed)
Well tolerated; first tolerated meal at 25.3 vs 32.6 hours, not significant
Limits: Small; mixed conditions; intravenous use only
It contains no growth hormone. It binds the ghrelin-type receptor on the pituitary and prompts a pulse of your own growth hormone, which the body’s feedback still controls.14
None of the studies cited here shows that in adults. The muscle and fat claims come from growth hormone itself and from reviews of the whole secretagogue class, which note few long, rigorous studies.4
The cortisol finding came from pigs. In people, the class carries a concern for higher blood sugar, and FDA cites antibody risk and serious adverse events with intravenous use. Long-term safety is poorly characterized.149
It helped in rats. In the 117-patient human trial, time to a first tolerated meal was shorter on ipamorelin but not significantly different from placebo.83
In published studies, ipamorelin was given by intravenous infusion. Pharmacy-prepared products, where a prescriber chooses to use them, are injected under the skin. That route has little published safety data, which FDA noted on its compounding page. Form and schedule are a prescriber’s decision.239
Ipamorelin has no FDA-approved dose. In people, it has only been given as weight-based infusions into a vein in research settings: single infusions in healthy men, and twice-daily infusions for up to a week in a hospital trial after bowel surgery. The dosage table lists those doses. No published trial has tested injections under the skin at home, and your clinician sets your dose.23
Ipamorelin has no FDA-approved dose. The only published human doses are weight-based infusions into a vein: single infusions in healthy men, and twice-daily infusions for up to a week in adults recovering from bowel surgery. No trial has tested injections under the skin. A clinician sets the actual dose.
Already have a prescribed dose? The peptide dosage calculator turns it into the units to draw on an insulin syringe.
Human trial · Infusion into a vein over 15 minutes
4.21 to 140.45 nmol/kg
Single dose2
Healthy men, eight per dose level; growth hormone rose at every dose
Human trial · Infusion into a vein
0.03 mg/kg
Twice daily for up to 7 days3
Adults in hospital after bowel resection; well tolerated, no clear benefit over placebo for gut recovery
A clinician makes the call. These are the questions they will ask first.
Vitals Vault peptide care starts with a blood panel and a licensed clinician, and ends with a retest.
Get early access to peptide care| Attribute | Ipamorelin | CJC-1295 |
|---|---|---|
| What it is | A ghrelin-mimicking secretagogue (five amino acids) | A growth hormone releasing hormone analog (GHRH-based) |
| Receptor | Ghrelin-type receptor | GHRH receptor |
| Duration in studies | Short; half-life about 2 hours | Short without DAC; days with DAC |
| FDA status | Not approved | Not approved |
The body does not release growth hormone steadily. The pituitary sends it out in pulses, with the largest one in deep sleep. Sleep, body fat, insulin and age all change how big a pulse the pituitary will give.
A secretagogue also keeps negative feedback in place, which reviewers list as one potential advantage over injecting growth hormone itself.4
A blood test before you start and a retest after shows what actually changed for you. It is how Vitals Vault approaches every treatment.
No. Ipamorelin is not FDA-approved for any use. FDA’s compounding safety page lists ipamorelin acetate in category 2 of the bulk drug substances under the 503B interim policy, added September 29, 2023. It cites immunogenicity risk, the complexity of characterizing a peptide with unnatural amino acids, and serious adverse events, including death, in a study that gave ipamorelin intravenously for gut motility. Ipamorelin is not one of the six peptides covered by the October 2026 enforcement-discretion policy.910
1998
Novo Nordisk researchers describe ipamorelin as the first selective growth hormone secretagogue.1
1999
Pharmacokinetic and pharmacodynamic modeling in healthy male volunteers.2
2014
Phase 2 trial in 117 bowel-surgery patients reports good tolerability and no significant benefit for postoperative ileus.3
September 29, 2023
FDA places ipamorelin acetate in category 2 under the 503B interim policy, citing safety risks.9

Ipamorelin is studied for prompting growth hormone release and, in one trial, for gut recovery after surgery. It is not FDA-approved to treat any condition.
It released growth hormone in healthy men and was designed to avoid raising cortisol. A phase 2 trial for postoperative ileus did not show a significant benefit over placebo. Claims about body composition, sleep or anti-aging rest mostly on the wider secretagogue literature.
It binds the ghrelin-type growth hormone secretagogue receptor on the pituitary and triggers a pulse of growth hormone. The body’s own feedback still controls the pulse.
In a seven-day surgery trial it was well tolerated. The secretagogue class carries some concern for higher blood sugar, and FDA flags immunogenicity and a report of serious adverse events, including death, with intravenous use. Long-term data are limited.
There is no FDA-approved dose. Human studies gave ipamorelin as weight-based infusions into a vein, once in healthy men and twice daily for up to a week after bowel surgery. Your clinician sets your dose.
Ipamorelin mimics ghrelin and acts on the ghrelin-type receptor. CJC-1295 is built on growth hormone releasing hormone and acts on the GHRH receptor. They hit different receptors on the same cells, which is why they are often discussed together.
No. Ipamorelin is not FDA-approved for any use. FDA lists ipamorelin acetate in category 2 for 503B compounding because of safety concerns, and it is not covered by the October 2026 policy for six other peptides.
It is not an approved drug, and FDA has not cleared it for compounding under its October 2026 policy. Vials sold online as "research use only" are not made for people.
Yes. The World Anti-Doping Agency prohibits growth hormone secretagogues in and out of competition.
Vitals Vault is opening clinician-led peptide care that starts with a blood test. Join the peptides waitlist to hear first. A licensed clinician reviews your history and labs and decides whether ipamorelin is right for you.

Vitals Vault is opening peptide care that starts with your blood work, is prescribed by licensed US clinicians and ends with a retest. Join the waitlist to hear first.