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What makes Ipamorelin "selective"?

In brief

The word comes from a 1998 paper that introduced ipamorelin as "the first selective growth hormone secretagogue": in animal models it triggered GH release while barely touching cortisol, ACTH, and prolactin — unlike earlier molecules of the class, which yanked several axes at once. Selectivity is a property of the pharmacological profile, documented preclinically — not proof of effects in humans.

Illustration for the research article

Chemical identity

Every value states its source: database, literature, or calculation. Calculated values are not presented as PubChem data.

Compound classSynthetic pentapeptide, growth hormone secretagogue
SynonymsИпаморелин · NNC 26-0161
Molecular formulaC38H49N9O5PubChem
Average molecular mass711.9 г/мольPubChem
CAS170851-70-4PubChem
PubChem CID9831659PubChem
Chain length5 остатковliterature
SequenceAib-His-D-2-Nal-D-Phe-Lys-NH2The sequence contains non-standard residues (Aib, D-2-naphthylalanine, D-phenylalanine) and an amidated C-terminus, so it is not written in one-letter code. The D-amino acids mean a stereoisomer shares the same mass: mass spectrometry alone does not confirm stereochemistry.

A term with a precise address

In 1998, Raun and colleagues at Novo Nordisk published a characterisation of a new pentapeptide in the European Journal of Endocrinology. The title spoke for itself: "the first selective growth hormone secretagogue". In their models ipamorelin triggered GH release while ACTH and cortisol levels stayed practically untouched even at high concentrations — a clear contrast with predecessors like GHRP-6.

A year later Kojima discovered ghrelin — the natural hormone whose receptor turned out to be the target of this whole molecular class. The puzzle clicked: secretagogues mimic the ghrelin signal.

What selectivity means technically

The pituitary runs several hormonal axes, and crude stimulation hits the neighbours: older secretagogues raised prolactin and cortisol along the way. "Selective", applied to ipamorelin, means a narrow profile: ghrelin-receptor activation with GH release — without meaningful shifts in the neighbouring axes. For a researcher that's valuable: the molecule gives a cleaner experimental signal.

What selectivity does NOT mean

It doesn't mean "safe", doesn't mean "effective in humans", doesn't mean "approved". Ipamorelin's clinical programme was started once — and never completed; systematic human efficacy data doesn't exist, and no medicine with this active substance exists either. Compounds of this class are also closed off by anti-doping lists.

In the catalogue, ipamorelin is a research material for laboratories studying the ghrelin axis and GH signalling. Its selective pharmacological profile is exactly what makes it valuable in that context.

References

  1. Ipamorelin, the first selective growth hormone secretagogue — European Journal of Endocrinology, 139(5), 552–561 (PMID 9849822; DOI 10.1530/eje.0.1390552), 1998.
  2. Ghrelin is a growth-hormone-releasing acylated peptide from stomach — Nature, 402, 656–660 (PMID 10604470; DOI 10.1038/45230), 1999.