Search volume treats ipamorelin and sermorelin as rival products. The documents treat them as two unrelated molecules that happen to push the same hormone: one a fragment of a human hormone with a regulatory history, the other a synthetic ghrelin mimic with almost none. This page lines up what each record actually contains.
The few amounts below come from pharmacokinetic studies and former labels, and every one is attributed and dated. They record what investigators infused, not what anyone should use.
Two doors into the same cell
Growth hormone is released from the pituitary when one of two signals arrives. Both compounds on this page copy one of them:
- Sermorelin is GRF(1–29): of the 44 residues in natural growth-hormone-releasing hormone, it keeps only the leading 29 — the minimum that still switches the receptor fully on. It binds the GHRH receptor. It sits in the same family as tesamorelin (the full 44-residue hormone, modified to last longer) and CJC-1295.
- Ipamorelin is a synthetic pentapeptide — five amino acids — that binds the ghrelin receptor (GHS-R), the receptor for the gut's hunger hormone. It sits in the other family, with GHRP-2, GHRP-6 and the oral MK-677.
That split is the whole reason they are sold as a pair: signalling through both receptors at once releases more growth hormone than either route alone, a finding the growth hormone secretagogues page covers. It is also why "which is better" is a slightly odd question. They are not two brands of one thing.
The records side by side
| Sermorelin | Ipamorelin | |
|---|---|---|
| What it is | GRF(1–29), a fragment of human GHRH | Synthetic pentapeptide, ghrelin mimic |
| Receptor | GHRH receptor | Ghrelin receptor (GHS-R) |
| Plasma half-life | ~10–20 minutes | ~2 hours (terminal) |
| FDA approval | Twice — Geref, 1990 and 1997; both since discontinued, safety and efficacy ruled out as the reason | Never, anywhere |
| ClinicalTrials.gov registrations (2026-09-28) | 27 | 3 |
| PubMed records (2026-09-28) | 333 | 54 |
| PubMed records tagged as randomised trials | 19 | 2 |
| What the trials studied | GH-deficiency diagnosis and treatment, HIV lipodystrophy, cognition, heart failure, fertility | Bowel-surgery recovery, and a pharmacokinetic study |
| Muscle or strength endpoint in trained adults | None | None |
| WADA status | Prohibited at all times | Prohibited at all times |
How long each lasts
Ipamorelin. The one human pharmacokinetic study, by Gobburu and colleagues (1999), infused ipamorelin into healthy men at five rates from 4.21 to 140.45 nmol/kg over 15 minutes, eight men per rate. The drug behaved in proportion to dose, with a terminal half-life of about 2 hours. Every dose produced a single pulse of growth hormone peaking at 0.67 hours, which then fell exponentially back to negligible levels.
Sermorelin. A 2003 review by Serono's drug-delivery group — the company that marketed Geref — puts its plasma half-life in humans at about 10–20 minutes, cleared mostly by filtration in the kidneys and by enzymes cutting the front end of the peptide. That short life is why the company spent years trying to extend it by attaching polyethylene glycol chains, and why modified versions such as tesamorelin exist at all.
Neither figure says anything about muscle. A longer half-life means the molecule lingers; the growth hormone response to both is still a pulse, not a steady elevation. Tesamorelin — the one approved drug in this family — has a half-life of 8 minutes on its current label, shorter than either.
The regulatory gap
This is the sharpest difference between the two, and the only one the documents state plainly.
Sermorelin was an approved medicine. EMD Serono's first Geref application (NDA 019863) dates from December 1990 and its second (NDA 020443) from September 1997 — one for a diagnostic strength, one for treatment vials. Neither is marketed now, and FDA's entries record a finding that matters for this comparison: the withdrawal was not a safety or efficacy decision. The document trail is on sermorelin.
Ipamorelin began as a Novo Nordisk research compound (code NNC 26-0161 in the company's 1998 rat studies); its clinical development, under Helsinn Therapeutics, ended after a phase 2 trial in 117 patients recovering from bowel surgery: patients on the drug reached solid food about seven hours sooner than those on placebo (medians of roughly 25 and 33 hours), a gap the trial could not distinguish from chance (p = 0.15). A 320-patient follow-on completed in 2013 with no results ever posted. No regulator has approved it, and FDA's compounding lists put it in category 2, the group flagged for safety concerns; the details are on ipamorelin.
What the evidence counts show
Sermorelin has roughly six times the literature and nine times the trial registrations. That is what three decades of pharmaceutical development leaves behind. But the purpose of those registrations matters more than their number: many of sermorelin's 27 use it as a diagnostic probe of the pituitary, and the remainder cover deficiency states, HIV-related fat, memory in later life, cardiac failure and infertility. The two that enrolled older adults for longer courses closed early, below 15 participants each.
Ipamorelin's three registrations are the two bowel-surgery trials and an unrelated multi-intervention study. Its PubMed record is dominated by anti-doping chemistry — methods for finding it in urine.
For the question the search is actually asking — muscle — the count is zero on both sides. Not one registration for either compound studies trained adults with a strength, lean-mass or performance endpoint.
The trial that does not exist
On 2026-09-28, PubMed held five records naming both ipamorelin and sermorelin. All five are reviews — of peptides in sports medicine, orthopaedics, doping and men's health. ClinicalTrials.gov lists no study that gives both. No one has ever put the two compounds against each other, or against placebo in the population that buys them.
What exists instead is the class-level picture. Where randomised trials do exist on this axis — tesamorelin, MK-677, capromorelin — lean mass rises by a little over one kilogram and strength does not measurably follow. There is no data suggesting either compound on this page exceeds that band, and no data measuring whether either reaches it. Tesamorelin vs ipamorelin sets the one approved compound against the unapproved one.
In sport
Both are prohibited at all times under section S2 of the WADA Prohibited List. Sermorelin is a growth-hormone-releasing factor by definition; ipamorelin is a ghrelin-receptor agonist, a class the list names. Sermorelin's former approval makes no difference to that. The class-wide detection record is on peptides and drug testing, and the compound-by-compound table on WADA status by compound.
What is established, and what is not
- Established: the two act on different receptors; sermorelin was twice an approved drug and ipamorelin never was; sermorelin has far more literature and registrations.
- Established: in healthy men ipamorelin's half-life is about 2 hours; sermorelin's is about 10–20 minutes.
- Not established: that either builds muscle or strength in trained adults — never tested for either.
- Not established: that either is more effective than the other at anything. The comparison has never been run.
Sources
- Gobburu JV, Agersø H, Jusko WJ, Ynddal L. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res 1999;16(9):1412–1416. PMID 10496658
- Esposito P, Barbero L, Caccia P, et al. PEGylation of growth hormone-releasing hormone (GRF) analogues. Adv Drug Deliv Rev 2003;55(10):1279–1291. PMID 14499707
- Johansen PB, Hansen KT, Andersen JV, Johansen NL. Pharmacokinetic evaluation of ipamorelin and other peptidyl growth hormone secretagogues with emphasis on nasal absorption. Xenobiotica 1998;28(11):1083–1092. PMID 9879640
- Beck DE, et al. Prospective, randomized, controlled, proof-of-concept study of the ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. Int J Colorectal Dis 2014. PMID 25331030
- FDA, Drugs@FDA: Geref, NDA 019863 and NDA 020443 (as recorded on this site's sermorelin entry, 2026-09-10).
- ClinicalTrials.gov intervention searches for sermorelin (27) and ipamorelin (3), 2026-09-28.
- PubMed searches, 2026-09-28:
sermorelin333;ipamorelin54;ipamorelin AND sermorelin5, all publication type Review; randomised-trial publication type: sermorelin 19, ipamorelin 2. - EGRIFTA SV (tesamorelin) prescribing information, section 12.3, via openFDA, read 2026-09-28.
- WADA Prohibited List, section S2.