Research peptides

Ipamorelin vs Sermorelin: Two Receptors, Two Histories

Both release growth hormone from the pituitary, through different receptors. One was approved for children; the other stopped at Phase 2 for lack of efficacy.

Written bySebastian Hunter, Founder and EditorI'm a 42-year-old senior advisor and distance runner who came to peptides as a sceptic. I'm not a doctor: I read the research, run my own experiment and keep honest notes. Read full bio

Published September 23, 2026Updated October 3, 2026

The short version

Ipamorelin and sermorelin both make the pituitary release growth hormone, but they press different buttons to do it. Sermorelin mimics growth hormone-releasing hormone. Ipamorelin acts on the ghrelin receptor. Sermorelin was an FDA-approved medicine for children until its maker stopped selling it. Ipamorelin never got past Phase 2, where it was dropped for not working well enough.

Different receptors: sermorelin acts on the GHRH receptor, ipamorelin on the growth hormone secretagogue (ghrelin) receptor.
Sermorelin had two FDA approvals, withdrawn in 2009 at the sponsor's request and not for safety or effectiveness.
Ipamorelin was never approved anywhere; its Phase 2 programme stopped for insufficient efficacy.
Ipamorelin's famous selectivity finding comes from rats and pigs, not people.
Both are prohibited in sport at all times under WADA S2.2.4.

Ipamorelin and sermorelin are usually sold as interchangeable “growth hormone peptides”. They share an end point: the pituitary releases more of its own growth hormone. They do not share a receptor, a structure, an evidence base or a regulatory history.

Side by side

	Sermorelin	Ipamorelin
What it is	GHRH(1-29)NH2: the first 29 amino acids of growth hormone-releasing hormone	A synthetic pentapeptide, Aib-His-D-2-Nal-D-Phe-Lys-NH2
Receptor	GHRH receptor on the pituitary	The GHRP receptor, later identified as the ghrelin receptor (GHS-R1a)
Human evidence	Controlled trials in children with growth hormone deficiency	A Phase 2 programme in postoperative ileus, discontinued for insufficient efficacy
Famous claim	Keeps the body’s feedback loop intact	GH release without an ACTH or cortisol rise, shown in rats and pigs
Tested in healthy adults for marketed uses?	No trial located	No trial located
Human half-life	Not established for the marketed adult use	Likely around 2 hours, from a Phase 1 study I could not retrieve
FDA history	Approved 1990 and 1997. Discontinued 2008. Approvals withdrawn 2009, not for safety or effectiveness	Never approved anywhere. FDA compounding category 2 (503B)
Evidence level on this site	Limited	Limited
WADA 2026	S2.2.4, growth hormone releasing factor	S2.2.4, growth hormone secretagogue

Full pages: Sermorelin · Ipamorelin

Same family, different receptors

The pituitary has more than one way to be told to release growth hormone. Sermorelin uses the direct one. It is a fragment of the hypothalamic hormone whose job is exactly that signal. A 1999 review describes it as specifically stimulating growth hormone secretion from the anterior pituitary. Prakash 1999 - Prakash A, Goa KL. Sermorelin: a review of its use in the diagnosis and treatment of children with idiopathic growth hormone deficiency. BioDrugs. 1999;12(2):139-57., in the references below

Ipamorelin uses the other route. The 1998 paper that characterised it reported that it acts through the GHRP receptor, a pathway the authors confirmed using GHRP and GHRH antagonists. That receptor was later identified as the ghrelin receptor. Raun 1998 - Raun K, Hansen BS, Johansen NL et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-61., in the references below

Ipamorelin’s evidence: animal pharmacology, then a failed trial

The 1998 paper found that in rat pituitary cells, anaesthetised rats and conscious pigs, ipamorelin released growth hormone with potency and efficacy similar to GHRP-6. It did so without raising ACTH or cortisol above the levels seen with GHRH. Raun 1998 - Raun K, Hansen BS, Johansen NL et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-61., in the references below That is a genuine finding, but it is animal and cell work, with no pharmacokinetic data in it.

In people, ipamorelin reached Phase 2 for postoperative ileus and was discontinued for insufficient efficacy. That history reaches me through a secondary reference; I could not locate a primary record of the trial results.

FDA’s compounding safety page places ipamorelin acetate in category 2 under its 503B interim policy. It states that a published study identified serious adverse events, including death, when ipamorelin was given intravenously for improving gastric motility. FDA does not name the study on that page, and I have not read it.

Limited human data

Small or uncontrolled human studies. Too little to settle the question either way. Selectivity data is in vitro and animal only. Human data is one paywalled Phase 1 PK study I could not retrieve, plus a Phase 2 ileus programme discontinued for insufficient efficacy.

Sermorelin’s evidence: real, and in children

The controlled evidence for sermorelin sits in paediatric growth hormone deficiency, which is what it was approved for. The 1999 review found limited data supporting once-daily treatment in some prepubertal children. It also found an unknown effect on final adult height and smaller height-velocity gains than with growth hormone itself. Prakash 1999 - Prakash A, Goa KL. Sermorelin: a review of its use in the diagnosis and treatment of children with idiopathic growth hormone deficiency. BioDrugs. 1999;12(2):139-57., in the references below

A six-month comparative trial in 43 prepubertal children found the lower sermorelin dose produced the lowest height velocity. The higher dose was comparable to growth hormone. Neyzi 1993 - Neyzi O, Yordam N, Ocal G et al. Growth response to growth hormone-releasing hormone(1-29)-NH2 compared with growth hormone. Acta Paediatr Suppl. 1993;388:16-21; discussion 22., in the references below

Limited human data

Small or uncontrolled human studies. Too little to settle the question either way. Controlled trials exist, but in children with growth hormone deficiency, and the review of them hedges the treatment data as limited. No trial in healthy adults for the marketed outcomes.

Both rate “limited” on this site, for opposite reasons. Sermorelin’s human trials showed an effect, in children. Ipamorelin’s human programme was stopped because it did not show enough of one.

The combination question

The two act on different receptors, so they are often sold together. The one study I located that combined sermorelin with ghrelin-receptor drugs is a retrospective chart review. Of 105 men on testosterone therapy prescribed GHRP-6, GHRP-2 and sermorelin together, 14 met the inclusion criteria, and their IGF-1 levels rose. Sigalos 2017 - Sigalos JT, Pastuszak AW, Allison A et al. Growth Hormone Secretagogue Treatment in Hypogonadal Men Raises Serum Insulin-Like Growth Factor-1 Levels. Am J Mens Health. 2017;11(6):1752-1757., in the references below

It did not include ipamorelin. It had no control group, measured a hormone marker rather than body composition, and cannot say which of the three peptides did what. It is not evidence for a stack, and this site does not endorse combining an unapproved research chemical with anything.

Regulatory status

Sermorelin

Ipamorelin

US legal status - Research use only

Sold for laboratory research use only. Not approved by the FDA for human use, and cannot be lawfully marketed as a supplement or a medicine. Products sold this way are not made to pharmaceutical quality standards, and their contents are not verified by anyone.

AU legal status - Not on the ARTG

Schedule 4 of the Poisons Standard, named directly, and Appendix D, clause 5 - prescription only, and possession without authority is illegal. Appendix D covers growth hormone secretagogues as a class as well. Nothing containing it is on the ARTG.

Regulators reach their own conclusions on their own timelines. Where these two disagree, the difference is the point - not an error.

Ipamorelin has never been approved by the FDA or any other regulator, for any indication. It is sold as a research chemical and is not legally marketed for human use in the US. FDA placed ipamorelin acetate in category 2 of its interim compounding policies, the category for nominated substances with potential significant safety risks.

Sport

Both are named in S2.2.4 of the WADA 2026 Prohibited List and are prohibited at all times. The US Anti-Doping Agency states that a therapeutic use exemption for sermorelin is highly unlikely to be approved.

What the comparison tells you

The two end at the same hormone but start at different receptors. Sermorelin completed a development programme for children and left the market, and FDA found in 2013 that it was not withdrawn for safety or effectiveness. Ipamorelin was tested in adults for a gut indication and stopped because it did not work well enough.

Neither history tells you what either does in a healthy adult who wants more muscle or better sleep. That trial has not been run for either one.

Common questions

What is the difference between ipamorelin and sermorelin?

They reach the same end point by different routes. Sermorelin is the first 29 amino acids of growth hormone-releasing hormone and acts on the GHRH receptor. Ipamorelin is a five-amino-acid growth hormone secretagogue that acts on the receptor later identified as the ghrelin receptor. Both prompt the pituitary to release its own growth hormone.

Which one has more human evidence?

Sermorelin has controlled trials, but in children with growth hormone deficiency. Ipamorelin reached a Phase 2 programme in postoperative ileus that was discontinued for insufficient efficacy. Neither has been tested in healthy adults for body composition, sleep or aging.

Is ipamorelin safer than sermorelin because it does not raise cortisol?

That claim rests on a 1998 study in rat pituitary cells, rats and pigs. It found ipamorelin released growth hormone without the ACTH and cortisol rise seen with GHRP-6 and GHRP-2. It has not been shown as a safety advantage in people, and the comparison was with other secretagogues, not with sermorelin.

Should ipamorelin and sermorelin be combined?

This site does not recommend combining an unapproved research chemical with anything. The only combination data I located is a retrospective chart review of 14 men given sermorelin with two other secretagogues. It measured an IGF-1 rise and had no control group, so it is not evidence for a stack.

Are ipamorelin and sermorelin banned in sport?

Yes. Both are on the WADA Prohibited List under S2.2.4 and are prohibited at all times. Ipamorelin is listed as a growth hormone secretagogue and sermorelin as a growth hormone releasing factor.

Does ipamorelin reduce belly fat?

No trial has tested that in people. Ipamorelin's only characterisation data is growth hormone release in rat pituitary cells, anaesthetised rats and conscious pigs. The only human programme is a Phase 2 trial in postoperative ileus, discontinued for insufficient efficacy. Neither measured fat mass. Growth hormone itself affects fat metabolism, but I found no body-composition study testing that link for ipamorelin.

Is there a peptide stronger than sermorelin?

I could not locate a controlled human trial comparing the potency of GH-releasing peptides head-to-head, including ipamorelin. Sermorelin and ipamorelin work through different receptors, so "stronger" is not one scale. Sermorelin completed paediatric trials showing a height-velocity effect, while ipamorelin's only human programme, in postoperative ileus, was stopped for insufficient efficacy. Neither result shows one is more potent than the other for the uses they are sold for now.

What is the "king" of growth hormone peptides?

No clinical measure ranks peptides this way. Ipamorelin, sermorelin and other growth hormone secretagogues act through different receptors. None has adult trials for muscle, sleep or fat loss, and none is FDA-approved for those uses. A claim naming one compound the strongest or best is marketing, not a finding from any trial I could locate.

Does sermorelin work the same as ipamorelin?

No. Both prompt the pituitary to release its own growth hormone, but through different receptors: sermorelin through the GHRH receptor, ipamorelin through the ghrelin receptor. Their evidence differs too. Sermorelin has paediatric trials showing a height-velocity effect, while ipamorelin's Phase 2 programme, in postoperative ileus, was stopped for insufficient efficacy. See the side-by-side table above.

References (10 sources)

Bibliographic detail is fetched from PubMed, not written by me - so a citation here cannot drift from the paper it names. Study design comes from PubMed's own tags rather than my judgement.

1.Raun K, Hansen BS, Johansen NL et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-61.StudyPMID 9849822
2.Prakash A, Goa KL. Sermorelin: a review of its use in the diagnosis and treatment of children with idiopathic growth hormone deficiency. BioDrugs. 1999;12(2):139-57.StudyPMID 18031173
3.Neyzi O, Yordam N, Ocal G et al. Growth response to growth hormone-releasing hormone(1-29)-NH2 compared with growth hormone. Acta Paediatr Suppl. 1993;388:16-21; discussion 22.Randomised trialPMID 8329826
4.Sigalos JT, Pastuszak AW, Allison A et al. Growth Hormone Secretagogue Treatment in Hypogonadal Men Raises Serum Insulin-Like Growth Factor-1 Levels. Am J Mens Health. 2017;11(6):1752-1757.StudyPMID 28830317full text
5.Federal Register, 4 March 2013 - Determination that GEREF (sermorelin acetate) injection was not withdrawn from sale for reasons of safety or effectiveness (Docket FDA-2012-P-1071). States both NDAs, their approval dates and indications, the 2008 discontinuation letters, and the withdrawal of approval effective 18 June 2009.- US Government Publishing Office (Federal Register)regulatory
6.USADA - Athletes, know sermorelin. States sermorelin is prohibited in sport and that a therapeutic use exemption is highly unlikely.- US Anti-Doping Agencyregulatory
7.FDA - Certain bulk drug substances for use in compounding that may present significant safety risks. Ipamorelin acetate is in category 2 under the 503B interim policy, with FDA's stated safety concerns.- US Food and Drug Administrationregulatory
8.WADA 2026 Prohibited List, section S2.2.4 - growth hormone releasing factors (sermorelin) and growth hormone secretagogues (ipamorelin) (national anti-doping agency mirror, PDF).- World Anti-Doping Agency (mirrored by the Jamaica Anti-Doping Commission)regulatory
9.Therapeutic Goods (Poisons Standard - June 2026) Instrument 2026, the current Poisons Standard (SUSMP). Ipamorelin is a Schedule 4 (prescription only) entry, and Appendix D, clause 5.- Federal Register of Legislation, Australian Governmentstatute
10.TGA - Unapproved therapeutic goods. Goods not on the ARTG have not been assessed by the TGA for safety, quality or effectiveness.- Therapeutic Goods Administration, Australian Governmentregulatory