Ipamorelin: Two Human Trials, and Nobody Has Seen the Second One

01What it is

Ipamorelin is a lab made chain of five amino acids, built at Novo Nordisk and characterised in 1998. It copies ghrelin, the hormone that makes you hungry, to trigger a burst of growth hormone from a gland at the base of the skull. I could find no published measurement of how tightly it binds the receptor it supposedly works through.

02What the trials found

Both trials were run by Helsinn, in patients whose bowels would not restart after surgery.

The published one, NCT00672074. 117 patients, ipamorelin into a vein twice a day for up to a week. The target was how long until someone could manage a solid meal. Ipamorelin got them there in 25.3 hours against 32.6 on placebo, a gap well inside what chance produces. The authors' own conclusion was that there were no significant differences between ipamorelin and placebo. (PMID 25331030) Nothing else they measured separated either.

The unpublished one, NCT01280344. 320 patients, 45 hospitals, doses up to twice as high. Finished May 2014.

Somebody looked, at 320 people, for three years, and the answer has sat somewhere private ever since.

Be precise about what is missing, because the registry entry is not blank. It lists all four arms and their doses: 0.03 mg/kg twice daily, 0.06 mg/kg twice daily, 0.06 mg/kg three times daily, and placebo. The doses are public. What has never been described is what happened.

03The selectivity claim, and the animal it was measured in

Every vendor page says the same thing: ipamorelin raises growth hormone cleanly, without the cortisol and prolactin that come with older peptides.

That comes from a single 1998 paper whose only listed affiliation is Novo Nordisk, the company that owned the molecule. The paper is real and says what it is quoted as saying. Its own abstract also contains the line that decides how much it is worth: "The specificity for GH release was studied in swine."

Every cortisol and prolactin measurement in that study was made in pigs.

Split the claim in two, because the study supports one half of it and not the other. On cortisol the assay worked. Both GHRP-6 and GHRP-2 raised ACTH and cortisol in those pigs, ipamorelin did not, and that separation held at doses more than 200 times the one needed for growth hormone (PMID 9849822).

On prolactin it is not a result at all. Prolactin did not rise for anything in that experiment, not ipamorelin and not either comparator, so nothing was distinguished from anything.

One of those comparators has since been measured in people. Given into a vein to healthy adults, GHRP-2 raises prolactin, along with ACTH and cortisol (PMID 9285939). So the prolactin channel of that pig assay stayed flat for a compound that demonstrably does raise prolactin in a human.

Picture a metal detector that catches the man with the crowbar and misses the man with the knife. It works, and you still cannot use it to tell you the queue is unarmed.

Nobody has replicated that study. And in humans the number is zero as far as I can establish: I found no cortisol or prolactin measurement for ipamorelin, at any dose, by any route.

04How it compares

Ipamorelin, GHRP-2, GHRP-6 and hexarelin all act on the same receptor ghrelin uses, and get sold as versions of one another. CJC-1295 and tesamorelin copy a different signal and hit a different receptor. Both routes end at growth hormone, which is why the stack story sounds plausible, but they are not interchangeable.

Read the last column. What ipamorelin's two trials measured is how soon a hospital patient could eat a solid meal. None of it transfers sideways.

05Where the dose came from

Every published human dose went into a vein. I found no published study following it through the body after an injection under the skin, which is the only route anyone actually uses.

The one human pharmacology study infused it into a vein in healthy men. Growth hormone came out as a single burst peaking around 40 minutes, then faded. (PMID 10496658) Every source quoting a half life of about two hours is quoting that study, and almost none mention it was a vein. Growth hormone works in pulses, so the shape of the signal is not a small detail.

The convention is 200 to 300 mcg under the skin, one to three times a day. Set that against what went into a patient in the trial that was published. About 4.2 mg a day into a vein. About 12.6 mg a day into a vein, in the 320 patient trial. The lowest rung of the only human escalation study was 210 mcg a day. Per day, the convention runs 5 to 21 times below the published trial dose.

So where does 200 to 300 mcg come from? I could not establish it, and I am not going to invent a lineage. Following the citations vendors offer leads nowhere. A 2026 review prints the dose a thousand times too small, crediting a paper published before ipamorelin was first described. (PMID 42123471)

06What could go wrong

On safety the paper and the FDA read the same data differently. Overall side effects were slightly lower on ipamorelin, which is where "well tolerated" comes from. Reviewing the trial in 2024, FDA noted more low potassium, more insomnia and more high blood sugar on ipamorelin, and two patients in that group died after surgery for colon cancer. FDA says plainly it is unclear whether those deaths had anything to do with the drug. What it is not is the frictionless safety record this is sold on.

FDA searched nine databases and reported it did not identify, in the published literature, any acute toxicity, repeat dose, genotoxicity, reproductive or carcinogenicity studies of ipamorelin. Its conclusion was that the nonclinical work that does exist is too limited in scope and duration to inform safety.

In mice given twice daily injections under the skin, ipamorelin increased fat pad weight relative to body weight and raised food intake. Growth hormone did the opposite, but only in growth hormone deficient mice; in mice with intact growth hormone it did not change fat at all. (PMID 11162489)

The rest of what could go wrong is not medical. WADA names ipamorelin explicitly under S2.2.4, growth hormone secretagogues. Prohibited at all times, in and out of competition, and non-Specified, which is the more serious tier and carries a four year default sanction. It is not part of any approved drug anywhere.

People still say ipamorelin is Category 2. That is true in one sense and misleading in another, because there are two separate compounding policies. On 27 September 2024 FDA moved ipamorelin acetate out of Category 2 under the 503A policy, because the two nominators withdrew their nominations. Nothing was resolved on the merits. Under the separate 503B policy, covering outsourcing facilities, ipamorelin acetate remains in Category 2, added 29 September 2023.

07What nobody knows

What is in the vial. Two independent groups testing illicit material found Gly-ipamorelin, ipamorelin with an extra amino acid on the front, instead of ipamorelin. One confirmed it against a custom synthesised reference standard (PMID 29864719); the other tested products seized by Danish customs and found the same change in every preparation it analysed, though it does not say how many. (PMID 30136411) Neither was measuring vial contents against the label, so this says nothing about what fraction of vials are affected.

Whether the slower growth signal rises in people. Insulin like growth factor 1 is what the liver puts out when growth hormone reaches it, and it is the lasting part of the signal, the thing growth hormone is actually wanted for. No study has reported it, at any dose, by any route.

08My take

Nobody ignored this molecule. Novo Nordisk designed it. Helsinn ran two controlled trials across more than sixty hospitals with real placebo groups and real patients. That is more genuine human evidence than BPC-157 and TB-500 have between them.

And the outcome is that one trial missed and the bigger one has never spoken. Somebody knows whether those higher doses did anything, and has known since 2014.

None of that is a claim that ipamorelin does nothing. Nobody has shown that either. The point is that the confident version, the clean selective one that raises growth hormone and nothing else, is not a summary of the evidence. It is a summary of one paper, about pigs, with the species left out.

If you run ipamorelin, or your clinic prescribes it, I want to know whether you have ever been shown a human trial for it, and which one. There are two. One is negative and the other has never reported.

Frequently asked

Do the human trials show that ipamorelin works?+

There are two registered human trials, both run by Helsinn in patients whose bowels would not restart after surgery. The published one, NCT00672074, gave 117 patients ipamorelin into a vein twice a day for up to a week and missed its target: 25.3 hours until someone could manage a solid meal against 32.6 on placebo, a gap well inside what chance produces, and the authors concluded there were no significant differences between ipamorelin and placebo. The larger one, NCT01280344, enrolled 320 patients at 45 hospitals at doses up to twice as high, finished in May 2014, and has never reported a result.

Does ipamorelin actually raise growth hormone, and does IGF-1 go up?+

One human pharmacology study infused ipamorelin into a vein in healthy men, and growth hormone came out as a single burst peaking around 40 minutes, then fading. Beyond that study, no human trial has looked at growth hormone levels, and no study has reported insulin like growth factor 1, the slower growth signal that follows behind it, for ipamorelin at any dose, by any route.

Does ipamorelin raise cortisol or prolactin like the older peptides?+

I could find no cortisol or prolactin measurement for ipamorelin in a person, at any dose, by any route. The selectivity claim traces to a single 1998 paper whose only listed affiliation is Novo Nordisk, the company that owned the molecule, and whose own abstract says the specificity work was done in swine. I found no replication of it.

Where does the 200 to 300 mcg number come from?+

It circulates as convention, 200 to 300 mcg under the skin, one to three times a day, and I could not establish where it came from. Every published human dose went into a vein instead, and per day the convention runs 5 to 21 times below the dose used in the trial that was published.

Is ipamorelin safe?+

The published trial reported slightly lower overall side effects on ipamorelin, which is where the well tolerated line comes from. Reviewing that same trial in 2024, FDA noted more low potassium, more insomnia and more high blood sugar on ipamorelin, and two patients in that group died after surgery for colon cancer, though FDA says plainly it is unclear whether those deaths had anything to do with the drug.

Is ipamorelin FDA approved, and is it banned in sport?+

It is not part of any approved drug anywhere. In sport, WADA names it explicitly under S2.2.4, growth hormone secretagogues, prohibited at all times and non-Specified, the tier carrying a four year default sanction.

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This content is for educational and informational purposes only and is not medical advice. Peptides discussed are research compounds and may not be approved for human use. Nothing here should be used to diagnose, treat, cure, or prevent any disease. Always consult a qualified healthcare professional before starting any peptide, supplement, or protocol. Individual responses vary. Do not self-administer compounds without proper medical supervision.