Hexarelin vs Ipamorelin
Research Comparison

Research Overview

Hexarelin vs ipamorelin compares two synthetic growth hormone (GH) secretagogues that act at the ghrelin receptor, GHS-R1a. Hexarelin is a hexapeptide GHRP analog carrying 2-methyl-tryptophan (Deghenghi et al., 1994); ipamorelin is a pentapeptide described in 1998 as the first selective GH secretagogue (Raun et al., 1998). Their published records differ in what happened to hormones besides GH (young adults for hexarelin, swine for ipamorelin), in how GH responses held up under repeated exposure, and in hexarelin's binding to CD36 in rat heart membranes (Bodart et al., 2002).

A PubMed search in October 2026 found no study comparing their effects on GH or other hormones; papers naming both are reviews and anti-doping studies. Disguised Alpha lists Hexarelin Acetate as a 5MG lyophilized vial and supplies ipamorelin as a lyophilized powder and in a 5MG/5MG blend with CJC-1295 No DAC, for laboratory research use only.

Structure and Class

Hexarelin is His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2, a GHRP analog in which tryptophan was replaced by the chemically more stable 2-methyl-tryptophan (Deghenghi et al., 1994). The product page lists C47H58N12O6 and 887.04 g/mol, the free peptide, matching PubChem CID 6918297; PubChem gives the 1:1 acetate as C49H62N12O8, 947.1 g/mol (CID 88325556).

Ipamorelin is Aib-His-D-2-Nal-D-Phe-Lys-NH2, from a series lacking the central Ala-Trp dipeptide of GHRP-1 (Raun et al., 1998). The product page lists C38H49N9O5 and 711.86 g/mol, matching PubChem CID 9831659.

Both carry a histidine near the amino end, a D-Phe-Lys-NH2 tail and two D-amino acids. Hexarelin keeps the Ala-Trp core and two indole rings; ipamorelin lacks that core, starts with 2-aminoisobutyric acid (Aib) and carries D-2-naphthylalanine where hexarelin has 2-methyl-D-tryptophan. Hexarelin is about 175 g/mol heavier, so a milligram of ipamorelin holds about 1.25 times as many molecules.

Side by Side

Research Context: Hexarelin

In anesthetized adult male rats, intravenous hexarelin released GH about as effectively as GHRP-6 at every amount tested, with peaks within 10 minutes (Deghenghi et al., 1994), and cells expressing human GHS-R1a gave a specific calcium response to it (Orkin et al., 2003). Models: rats, transfected cells.

Hexarelin also binds CD36. A photoactivatable hexarelin derivative labeled an 84 kDa protein in rat cardiac membranes whose N-terminal sequence matched rat CD36. Hexarelin raised coronary perfusion pressure in perfused hearts, but not in hearts from CD36-null mice or from spontaneously hypertensive rats deficient in CD36 (Bodart et al., 2002). Models: rat cardiac membranes, perfused rat and mouse hearts.

In six young adults given two intravenous amounts, hexarelin and GHRP-2 gave similar GH responses, larger than after GHRH. Both raised prolactin, less than TRH did, and ACTH and cortisol, about as much as human corticotropin-releasing hormone did; the authors called neither fully specific (Arvat et al., 1997). Model: young adults.

In the transfected cells, the calcium response to hexarelin was markedly desensitized 2 to 5 minutes after a first exposure at 100 nM (Orkin et al., 2003). In young beagle dogs exposed for six weeks, GH responses to hexarelin and GHRH challenges both peaked at week 3; by week 6 the GHRH response was back at its starting level and the hexarelin response below it (Rigamonti et al., 1999).

In older adults exposed twice daily for 16 weeks, the GH response to a hexarelin test fell to about 55 percent of baseline and was back at baseline 4 weeks after the course, with no significant change in IGF-I (Rahim et al., 1998); the cortisol response also fell and recovered, while ACTH and prolactin responses did not change significantly (Rahim et al., 1999). Models: cells, dogs, older adults.

Research Context: Ipamorelin

Ipamorelin released GH from primary rat pituitary cells with potency similar to GHRP-6, acted through a GHRP-like receptor rather than the GHRH receptor in antagonist profiling, and performed comparably to GHRP-6 in rats and swine. In the swine, none of the secretagogues tested changed FSH, LH, prolactin or TSH; GHRP-6 and GHRP-2 raised ACTH and cortisol, but ipamorelin did not raise either beyond GHRH levels, even at more than 200 times its ED50 for GH release (Raun et al., 1998). Hexarelin was not tested. Models: rat pituitary cells, rats, swine.

In healthy men given 15-minute intravenous infusions at five ascending rates, ipamorelin had a terminal half-life of about 2 hours and produced a single GH episode peaking near 40 minutes (Gobburu et al., 1999). Its abstract reports only ipamorelin and GH concentrations. Model: healthy men.

In adult female rats exposed three times daily for 15 days, the GH response to an intravenous ipamorelin challenge was marginally reduced, while the GHRH response, pituitary GH content and total IGF-I were unchanged (Johansen et al., 1999). PubMed returned no ipamorelin study of receptor desensitization in cells or of CD36 in October 2026. Model: rats.

A placebo-controlled phase 2 trial in 114 adults after bowel resection found no significant difference from placebo in its key and secondary efficacy analyses (Beck et al., 2014). FDA's list of bulk drug substances that may present significant safety risks places ipamorelin acetate in category 2 under its 503B interim policy, citing possible immunogenicity, unnatural amino acids and a published study reporting serious adverse events, including death, with intravenous ipamorelin for gastric motility.

Choosing Between Them for a Research Question

GH release with ACTH and cortisol no higher than after GHRH has its precedent with ipamorelin, in swine (Raun et al., 1998). CD36 and coronary perfusion (rat and mouse hearts), and the prolactin, ACTH and cortisol release that came with GH in young adults, have theirs with hexarelin (Bodart et al., 2002; Arvat et al., 1997).

The records do not line up: the hormone panels come from different species, and the GHRH-controlled challenge studies from dogs and rats on different schedules. A head-to-head design would use equimolar amounts in one species (1 µmol is 0.887 mg of hexarelin free peptide or 0.712 mg of ipamorelin), read GH with prolactin, ACTH and cortisol, and include a GHRH challenge as the internal control both challenge studies used (Rigamonti et al., 1999; Johansen et al., 1999).

The growth hormone secretagogues guide covers the wider family; the hexarelin and ipamorelin guides cover each compound.

Handling and Storage

Both are lyophilized powders, and both product pages list -20°C for the powder as shipped and 2 to 8°C after reconstitution, protected from light, with freeze/thaw cycles avoided. Let the sealed vial reach room temperature before opening, add diluent slowly down the wall, swirl rather than shake, and aliquot.

Hexarelin keeps one tryptophan beside the more stable 2-methyl-tryptophan (Deghenghi et al., 1994), so limit light and air. For molar work, use the measured content on the lot certificate in the COA portal; the ipamorelin IP01 certificate reports 10.58 mg against a 10 mg label. The hexarelin listing, named Hexarelin Acetate, gives the free-peptide formula and shows no lot certificate as of October 2026; 1 µmol of the 1:1 acetate is 0.947 mg.

Questions Researchers Ask

Hexarelin vs ipamorelin: what is the difference?

Both release GH through the ghrelin receptor. Hexarelin, a six-residue GHRP-6 analog, also binds CD36 in rat heart membranes (Bodart et al., 2002) and raised prolactin, ACTH and cortisol in young adults (Arvat et al., 1997); ipamorelin, a five-residue peptide, did not raise ACTH or cortisol beyond GHRH levels in swine (Raun et al., 1998).

Ipamorelin vs hexarelin: which is more selective for GH?

Ipamorelin, on the published data, with a caveat: its selectivity was shown in swine (Raun et al., 1998) and hexarelin's broader release in people (Arvat et al., 1997), and a PubMed search found no study comparing their hormone responses.

Does the GH response fade with repeated exposure?

Partly, in the studies cited here. Hexarelin's fell to about 55 percent of baseline over 16 weeks in older adults and recovered after the course ended (Rahim et al., 1998); ipamorelin's response to a challenge was marginally reduced after 15 days in rats (Johansen et al., 1999).

Does ipamorelin bind CD36 like hexarelin?

Unknown: PubMed returned no ipamorelin study at CD36 in October 2026. Hexarelin's CD36 action was defined in perfused hearts, where CD36-null mouse hearts did not respond (Bodart et al., 2002).

Are hexarelin and ipamorelin approved or prohibited in sport?

Neither is an FDA-approved drug: Drugs@FDA lists no product for either, and a 2018 review reported that the GHRPs it discussed, hexarelin among them, were not FDA approved (Sigalos and Pastuszak, 2018). The 2026 WADA Prohibited List names ipamorelin and examorelin (hexarelin) under S2.2.4, in class S2, prohibited at all times.