Ipamorelin vs Sermorelin: What the Research Shows

Ipamorelin vs Sermorelin: Mechanisms, Human Data and Regulatory Status

By Medical Team of Generic Peptides

Quick answer. Ipamorelin vs sermorelin is a comparison of two peptides that raise growth hormone (GH) by different routes. Sermorelin is the active 29-amino-acid fragment of growth hormone–releasing hormone (GHRH) and acts on the GHRH receptor; it was once an FDA-approved drug. Ipamorelin is a five-amino-acid ghrelin-receptor agonist that was never approved. Each has its own human data, but no published study has compared them head to head. Both are prohibited in sport.

Ipamorelin vs Sermorelin: Two Different Receptors

Growth hormone release from the pituitary is controlled by several signals. Two of them are stimulatory: GHRH from the hypothalamus, and ghrelin, a hormone made largely in the stomach. Each acts through its own receptor on the pituitary's somatotroph cells. Ipamorelin and sermorelin each mimic one of these signals.

Sermorelin is GRF(1-29)-NH2, the first 29 amino acids of human GHRH. A review described it as the shortest synthetic peptide with the full biological activity of GHRH [8]. It binds the GHRH receptor, the same target as tesamorelin, Mod GRF 1-29 and CJC-1295.

Ipamorelin is a synthetic pentapeptide, Aib-His-D-2-Nal-D-Phe-Lys-NH2, developed by Novo Nordisk in the 1990s [1]. It activates the growth hormone secretagogue receptor (GHS-R1a), better known as the ghrelin receptor — the same receptor targeted by GHRP-2, GHRP-6 and the oral compound MK-677.

The two molecules are also very different in size: ipamorelin weighs about 712 Da, while sermorelin weighs about 3,358 Da [11].

Ipamorelin vs Sermorelin at a Glance

What Ipamorelin Research Shows

Selectivity in animals (1998). The study that introduced ipamorelin compared it with GHRP-6 and GHRP-2 in rat pituitary cells, anesthetized rats and conscious swine [1]. Its GH-releasing potency was similar to GHRP-6. What set it apart was selectivity: in swine, GHRP-6 and GHRP-2 raised ACTH and cortisol, while ipamorelin did not raise them beyond the levels seen with GHRH — even at doses more than 200 times higher than those needed for GH release. None of the compounds changed FSH, LH, prolactin or TSH.

Pharmacokinetics in healthy men (1999). In a study of 40 healthy men given ipamorelin by 15-minute intravenous infusion at five dose levels, exposure rose in proportion to dose, the terminal half-life was about 2 hours, and each infusion produced a single GH peak about 40 minutes after the start [2].

Postoperative ileus trial (2014). The only published efficacy trial tested ipamorelin as a gut-motility agent after bowel surgery. In a Phase 2, double-blind, placebo-controlled study of 114 patients, median time to first tolerated meal was 25.3 hours with ipamorelin and 32.6 hours with placebo — a difference that was not statistically significant (p = 0.15) [3]. A second, larger Phase 2 trial was completed in 2014, but no results have been posted [4]. ClinicalTrials.gov lists no Phase 3 trial.

Bone studies in rats. In adult female rats treated for 12 weeks, ipamorelin increased bone mineral content, mainly by increasing bone size rather than bone density [5].

None of these studies measured muscle mass, fat loss or other body-composition outcomes in humans. For more background, see our ipamorelin research guide.

What Sermorelin Research Shows

Sermorelin has a longer clinical history because it was developed as a drug.

Regulatory history. The FDA approved sermorelin acetate (Geref, EMD Serono) on December 28, 1990, with a second dosage form approved in 1997 [9]. Both products were later discontinued. In 2013, the FDA formally determined that Geref was not withdrawn from sale for reasons of safety or effectiveness [10].

GH-deficient children (1996). In a multicenter study of prepubertal children with GH deficiency, once-daily subcutaneous GHRH therapy increased mean height velocity from 4.1 cm per year to 8.0 cm per year at six months and 7.2 cm per year at twelve months, among the 86 children included in the efficacy analysis [6]. A later review noted that gains in height velocity were smaller than with recombinant growth hormone, and that facial flushing and injection-site pain were the most common adverse events [8].

Healthy older men (1997). In 11 healthy men aged 64–76, single nightly injections of GHRH(1-29) for six weeks increased nocturnal GH secretion, but IGF-1, body composition measured by DEXA, muscle histology and lipids did not change [12]. Two of six strength measures improved. The authors noted that single nightly administration was less effective than multiple daily administration.

Half-life. The European product information for Geref gives a plasma half-life of 6–7 minutes after intravenous administration, with the GH response peaking at about 30 minutes and lasting 2–3 hours [7].

For a full review, see our sermorelin research guide.

Does Ipamorelin Work Better Than Sermorelin?

This is one of the most common questions about ipamorelin vs sermorelin, and the research cannot answer it. No published study has compared the two directly, and the human studies that exist used different populations, routes, designs and endpoints:

• Ipamorelin's human data come from healthy young men (pharmacokinetics) and surgical patients (gut motility).
• Sermorelin's come from GH-deficient children and small groups of older men.

What can be compared is pharmacology. Ipamorelin is longer-lived in plasma (about 2 hours versus minutes) and, in animal studies, did not raise cortisol or ACTH. Sermorelin acts on the hypothalamic GHRH pathway and has the longer track record as an approved drug. Neither has shown improvements in body composition in a controlled human trial — and in the sermorelin study that measured it, body composition did not change [12].

Can Sermorelin and Ipamorelin Be Studied Together?

Researchers often pair a GHRH analog with a ghrelin-receptor agonist because the two pathways interact. In a 1990 study of healthy men, GHRP-6 combined with GHRH produced a larger GH response than either alone — a synergistic effect [13]. That study used GHRP-6 and full-length GHRH(1-44), not ipamorelin or sermorelin, so it supports the general principle rather than this specific pair. We found no published study of ipamorelin and sermorelin given together.

The most common pairing on the research market uses a different GHRH analog, Mod GRF 1-29; we review it in CJC-1295 and ipamorelin, and the GHRH analogs themselves in CJC-1295 DAC vs No DAC.

Safety Findings From Studies

• Ipamorelin. In the Phase 2 surgical trial, treatment-emergent adverse events occurred in 87.5% of ipamorelin patients and 94.8% of placebo patients, a population recovering from bowel surgery [3]. The FDA has cited immunogenicity concerns and the presence of unnatural amino acids, and notes a published report of serious adverse events, including death, with intravenous use for gastric motility [15].
• Sermorelin. In pediatric use, the most common adverse events were facial flushing and injection-site pain [8].
• Both. Neither has long-term safety data in healthy adults, and both raise GH and, potentially, IGF-1, which is the main theoretical concern with any GH-axis stimulant.

Ipamorelin and Sermorelin: FDA and WADA Status

Checked October 24, 2026.

Ipamorelin. Ipamorelin is not an FDA-approved drug. It was removed from Category 2 of the FDA's interim 503A policy effective September 27, 2024, after its nomination was withdrawn [14]. At its October 29, 2024 meeting, the Pharmacy Compounding Advisory Committee voted 0 in favor, 12 against and 1 abstaining on adding either ipamorelin form to the 503A bulks list, citing a lack of information supporting safety and efficacy [16]. Ipamorelin acetate remains in Category 2 of the FDA's separate 503B policy for outsourcing facilities [15].

Sermorelin. Sermorelin was an FDA-approved drug, and the FDA's 2013 determination that Geref was not withdrawn for safety or effectiveness reasons allows generic applications that reference it [10]. No sermorelin product is currently marketed under an approved application.

WADA. The 2026 Prohibited List names both peptides under S2.2.4, growth hormone–releasing factors: sermorelin as a GHRH analogue and ipamorelin as a growth hormone secretagogue [17]. Both are prohibited at all times.

For the wider 2026 regulatory picture, see our report on the FDA's interim access policy for peptides.

Verifying Ipamorelin and Sermorelin on a COA

Because the two molecules differ in mass by more than 2,600 Da, mass spectrometry distinguishes them easily: about 712 Da for ipamorelin and about 3,358 Da for sermorelin. A useful certificate of analysis should show the measured mass, HPLC purity and a lot number that matches the vial. Note that sermorelin and Mod GRF 1-29 differ by only about 10 Da, so a sermorelin COA should come from a high-resolution instrument. Our guide on how to read a research peptide COA explains each section.

Generic Peptides supplies ipamorelin and sermorelin for laboratory research with lot-specific COAs. Both are listed in our Growth Hormone & IGF-1 category, alongside tesamorelin and other GHRH analogs.

FAQ

What is the difference between ipamorelin and sermorelin?

Sermorelin is a GHRH analog that acts on the GHRH receptor; ipamorelin is a ghrelin-receptor agonist. They stimulate growth hormone release through different receptors on the same pituitary cells.

Does ipamorelin work better than sermorelin?

There is no head-to-head study. Ipamorelin lasts longer in plasma (about 2 hours versus minutes) and was selective for GH in animal studies, while sermorelin has the longer clinical history as an approved drug.

Can sermorelin and ipamorelin be used together?

No published study has tested this specific combination. A 1990 human study found that a GHRH and a GH-releasing peptide (GHRP-6) together produced a larger GH response than either alone.

Is sermorelin FDA approved?

Sermorelin (Geref) was approved in 1990 and later discontinued; the FDA determined in 2013 that it was not withdrawn for safety or effectiveness reasons. Ipamorelin has never been approved.

Are ipamorelin and sermorelin banned in sports?

Yes. Both are named under WADA's 2026 Prohibited List section S2.2.4 and are prohibited at all times.

References

For research use only. Not for human consumption. This content is for informational purposes and is not medical advice.