Ipamorelin vs Sermorelin: What the Research Compares

People search “ipamorelin vs sermorelin” as if they were two versions of one thing. In the published research they enter the growth hormone axis at different points. This page sets the two summaries side by side, shows what each body of work tested, and says where a direct comparison cannot be made.

Quick facts, side by side

• What each is: Sermorelin is a synthetic analog built from the first 29 amino acids of the 44-amino-acid GHRH, the shortest fragment that keeps full activity. Ipamorelin is a five-amino-acid peptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2) of 711.9 g/mol (PubChem).
• The receptor: Sermorelin binds the GHRH receptor on the pituitary cells that make growth hormone (Regulation of the pituitary somatotroph cell by GHRH and its receptor). Ipamorelin acts on the ghrelin receptor, the same receptor as GHRP-6 (Raun et al., 1998).
• First description: sermorelin is one of the most extensively characterized growth hormone secretagogues in the literature. Ipamorelin was first described in 1998 by Novo Nordisk researchers, in rat pituitary cells, rats and pigs.
• Human data for ipamorelin: one pharmacokinetic study in healthy men, where the half-life was about 2 hours and growth hormone came in a single pulse peaking at 0.67 hours (Gobburu et al., 1999), and one published phase 2 trial in adults after bowel surgery.
• Human data for sermorelin: a long record in children with idiopathic growth hormone deficiency and in testing how well the pituitary can respond (Sermorelin review). The research describes a short circulating half-life on the order of minutes. The ipamorelin and sermorelin timing numbers come from different studies and are not a head-to-head measurement.
• Approval: sermorelin was approved as Geref in 1990 and again in 1997, then withdrawn effective 2009-06-18, and the Federal Register determination states it was not withdrawn for reasons of safety or effectiveness (Federal Register). We found no drug approval for ipamorelin from the FDA or any other regulator. In September 2023 the FDA added ipamorelin acetate to its list of bulk drug substances that may present significant safety risks when used in compounding (FDA).

What the studies tested

Each item below tested one compound.

Ipamorelin, in animals and two small human studies. In rat pituitary cells, rats and pigs, researchers reported that ipamorelin triggered growth hormone release and, unlike GHRP-6 and GHRP-2, did not raise ACTH or cortisol in pigs beyond the levels seen with GHRH (Raun et al., 1998). In a randomized, placebo-controlled trial of adults after bowel surgery, 117 patients enrolled and 114 were analyzed. The main measure was time to tolerating a standard solid meal, and researchers found no statistically significant difference from placebo, a median of 25.3 hours versus 32.6 hours (Beck et al., 2014). A second, larger phase 2 trial is listed as completed in 2014 with no results posted on the registry.

Sermorelin, in the pituitary and growth hormone axis. The work centers on the GHRH receptor and what the pituitary releases in response. Because sermorelin works through the receptor and not around it, the body’s natural brake on growth hormone release, somatostatin, still applies. In older adults, effects on measured growth hormone and IGF-1 are consistent and well replicated, and downstream effects are smaller and vary between studies.

Where they differ, and where they cannot be compared

A GHRH analog and a ghrelin receptor agonist are not interchangeable tools, even where both raise growth hormone. They engage the axis at different points and are subject to different feedback dynamics. The human evidence points at different questions too: pituitary responsiveness and a pediatric record for sermorelin, a gut-recovery trial that missed its main goal for ipamorelin.

None of the studies cited on this page tested both compounds, and they used different populations, endpoints and time frames. The work does not say which is the better tool for any given question. It says what each was used to ask.

Related research

• Ipamorelin: what the research shows
• Sermorelin research
• Tesamorelin vs Ipamorelin

Common questions

Do ipamorelin and sermorelin work the same way?

No. Sermorelin acts on the GHRH receptor and ipamorelin acts on the ghrelin receptor. Both raise growth hormone release, through two separate receptor systems.

Does either have an FDA approval?

Sermorelin was approved as Geref and withdrawn effective 2009-06-18, a commercial exit and not a safety or effectiveness finding. We found no approval for ipamorelin anywhere. Neither statement is about a research compound sold for laboratory use.

Have any studies compared the two directly?

None of the studies cited on this page tested both. Each tested one compound, in its own models and with its own endpoints.

How strong is the evidence for each?

Sermorelin has the longer record, with an approval history and a consistent growth hormone and IGF-1 response. Ipamorelin’s record is thin, mostly older and mostly preclinical, and its larger human trial missed its main goal.

For laboratory research use only. Not for human or animal consumption. This page summarizes published studies and is not medical advice.