Ipamorelin vs GHRP-2
Research Comparison

Research Overview

Ipamorelin vs GHRP-2 compares two synthetic agonists of the ghrelin receptor, GHS-R1a (Vodnik et al., 2016). GHRP-2, also written GHRP 2 and named pralmorelin, is a hexapeptide from the growth hormone releasing peptide (GHRP) series of Polygen and Tulane University (Drugs R D, 2004). Ipamorelin is a pentapeptide that Novo Nordisk described in 1998 as the first selective growth hormone (GH) secretagogue (Raun et al., 1998).

In that paper's swine tests, GHRP-2 raised ACTH and cortisol, while after ipamorelin both stayed at levels not significantly different from those after GH releasing hormone (GHRH) (Raun et al., 1998), so the comparison turns on which hormones each paper measured, in which model, and on two different regulatory records. Disguised Alpha supplies ipamorelin as a lyophilized powder for laboratory research use only and does not list GHRP-2. Nothing on this page is guidance for use in people.

Structure and Class

Both are short amidated peptides built partly from D-amino acids and non-natural residues. GHRP-2 is D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2, where D-2-Nal is 3-(2-naphthyl)-D-alanine. PubChem lists the free base as C45H55N9O6, 818.0 g/mol (CID 6918245), and the dihydrochloride, the salt the developer tested as KP-102 (Doi et al., 2004), as 890.9 g/mol (CID 9940988).

Ipamorelin, Aib-His-D-2-Nal-D-Phe-Lys-NH2 (Aib, 2-aminoisobutyric acid), came from a series lacking the central Ala-Trp dipeptide of GHRP-1 (Raun et al., 1998). Both carry D-2-Nal and end in D-Phe-Lys-NH2; GHRP-2 keeps Ala-Trp between them, and ipamorelin opens with Aib-His instead of D-alanine. The product page lists C38H49N9O5 and 711.86 g/mol, matching PubChem CID 9831659. GHRP-2's tryptophan is prone to oxidation; ipamorelin has none. Per milligram of free peptide, ipamorelin holds about 15 percent more molecules (1.40 against 1.22 µmol).

Side by Side

Research Context: Ipamorelin

In rat pituitary cells, ipamorelin released GH with potency similar to GHRP-6 (EC50 1.3 nmol/l) through a GHRP-like receptor, not the GHRH receptor. In swine, no secretagogue tested changed FSH, LH, prolactin or TSH; GHRP-6 and GHRP-2 raised ACTH and cortisol, but ipamorelin did not raise either significantly beyond GHRH levels, even at more than 200 times its ED50 for GH release (Raun et al., 1998).

In healthy men given intravenous infusions at five escalating rates, ipamorelin showed a terminal half-life of about two hours and one GH episode peaking near 40 minutes. The abstract reports only ipamorelin and GH (Gobburu et al., 1999), so its ACTH, cortisol and prolactin data come from swine. In male rats, its systemic clearance was five times lower than that of GHRP-6, and its nasal bioavailability was about 20 percent against about 50 percent for GHRP-2 (Johansen et al., 1998).

A double-blind, placebo-controlled phase 2 trial in 114 adults after bowel resection found no significant difference in the key or secondary efficacy analyses; adverse events occurred in 87.5 percent on ipamorelin and 94.8 percent on placebo (Beck et al., 2014). No ipamorelin drug has been approved. Since September 29, 2023, the FDA list of bulk drug substances that may present significant safety risks has placed ipamorelin acetate in 503B category 2, citing possible immunogenicity for certain routes, unnatural amino acids and a published report of serious adverse events, including death, with intravenous ipamorelin for gastric motility.

Research Context: GHRP-2

In the same swine study, GHRP-2 was more potent than ipamorelin and GHRP-6 but reached a lower GH maximum than either (Raun et al., 1998). In conscious rats it raised ACTH and corticosterone but not prolactin (Doi et al., 2004); it did not release ACTH from cultured rat pituitary cells, and a CRF antagonist, not an AVP antagonist, markedly blocked its ACTH response, which the authors read as a hypothalamic action mainly through CRF (Hirotani et al., 2005).

In six healthy young adults, intravenous GHRP-2 raised GH more than GHRH did, prolactin less than TRH did, and ACTH and cortisol about as much as human CRH did (Arvat et al., 1997).

The cortisol response has been studied as a test of the adrenal axis: in 254 people evaluated for hypopituitarism it tracked the insulin tolerance test (r = 0.777), though the authors judged it a substitute only in men without a functional adenoma (Hayakawa et al., 2018). In ten children with short stature, the GHRP-2 elimination half-life was about 0.55 hours (Pihoker et al., 1998).

A 2004 drug profile reports that GHRP-2 awaited approval in Japan as a diagnostic agent for hypothalamo-pituitary function and that US phase II development with Wyeth for GH deficiency appeared to have been discontinued (Drugs R D, 2004). Japan's KP-102 Study Group validated a single intravenous GHRP-2 test in 77 healthy adults and 58 with GH deficiency: mean peak GH was 84.6 against 1.36 µg/l (Chihara et al., 2007).

By 2016 GHRP-2 was the only ghrelin receptor ligand from clinical trials to reach the market, approved in Japan for diagnostic purposes (Vodnik et al., 2016). Since September 29, 2023, the FDA list has placed GHRP-2 for injectable and nasal routes in 503B category 2, citing immunogenicity risk and reports of serious adverse events in people who received it, including a higher insulin requirement, deaths of critically ill study subjects, infection and pancreatitis, with causality not established.

Choosing Between Them for a Research Question

Choose by the hormone panel the question needs. Ipamorelin is the documented contrast when ACTH and cortisol should stay near GHRH levels, a finding made in swine (Raun et al., 1998). GHRP-2 fits designs that read the adrenal axis beside GH, need the higher potency per nanomole it showed in swine, or link to the diagnostic-test literature (Chihara et al., 2007).

A PubMed search in October 2026 found no study besides the 1998 swine work whose abstract reports ACTH or cortisol after both. A head-to-head design needs equimolar amounts, GH, ACTH, cortisol and prolactin at matched times (corticosterone in rats), and sampling long enough for the more slowly cleared peptide in the species studied. The human half-lives come from separate studies in different populations, about two hours for ipamorelin in healthy men (Gobburu et al., 1999) and about half an hour for GHRP-2 in children (Pihoker et al., 1998), so they are not a head-to-head measure.

Handling and Storage

Ipamorelin ships lyophilized, and its product page lists -20°C for the powder as shipped and 2 to 8°C after reconstitution, protected from light, with freeze/thaw cycles avoided. GHRP-2 is usually handled the same way and kept dark for its tryptophan. Bring a sealed vial to room temperature before opening, add diluent down the wall, swirl rather than shake, and split stock into single-use aliquots.

Base molarity on measured content and on the form the certificate names. For ipamorelin lot IP01, the certificate in the COA portal reports 10.58 mg net peptide against a 10 mg label. For GHRP-2, check which form a certificate names, such as the free base (818.0 g/mol), the dihydrochloride (890.9 g/mol) or an acetate salt.

Questions Researchers Ask

Ipamorelin vs GHRP-2: what is the difference?

Both are synthetic ghrelin receptor agonists. Ipamorelin, a pentapeptide, did not raise ACTH or cortisol beyond GHRH levels in swine, while GHRP-2, a hexapeptide, raised both and was more potent per nanomole (Raun et al., 1998). GHRP-2 reached the market in Japan as a diagnostic agent (Vodnik et al., 2016); ipamorelin has no approval.

GHRP-2 vs ipamorelin: which is more selective?

Ipamorelin, with a caveat. In swine, GHRP-2 raised ACTH and cortisol and ipamorelin did not, while neither changed prolactin (Raun et al., 1998). In six healthy young adults given intravenous GHRP-2, prolactin, ACTH and cortisol rose with GH (Arvat et al., 1997), but the human ipamorelin kinetics study reports GH only (Gobburu et al., 1999), and a PubMed search in October 2026 found no human study reporting ipamorelin's ACTH, cortisol or prolactin response.

Is GHRP-2 an approved drug?

Only for diagnostic purposes, in Japan (Vodnik et al., 2016), where its GH test was validated in adults (Chihara et al., 2007). US phase II development for GH deficiency appeared to have been discontinued by 2004 (Drugs R D, 2004).

Are ipamorelin and GHRP-2 prohibited in sport?

Yes. The 2026 WADA Prohibited List names ipamorelin among growth hormone secretagogues and GHRP-2 (pralmorelin) among GH-releasing peptides, both in section S2.2.4, in class S2, which is prohibited at all times.

Does Disguised Alpha sell GHRP-2?

Not currently. Disguised Alpha supplies ipamorelin for laboratory research, as Ipamorelin, in the CJC-1295 No DAC & Ipamorelin blend and in the Tesamorelin & Ipamorelin blend.