What Is Ipamorelin? Structure and Published Literature

Ipamorelin is a synthetic five-residue peptide, Aib-His-D-2Nal-D-Phe-Lys-NH2, that acts on the growth hormone secretagogue receptor, also known as the ghrelin receptor. Its formula is C38H49N9O5, its average molecular weight about 711.9 Da and its CAS number 170851-70-4. It was described in 1998 as the first selective growth hormone secretagogue [1].

What do the unusual residues mean?

Three of its five residues are not among the 20 standard amino acids. Aib is alpha-aminoisobutyric acid. D-2Nal is the D-isomer of 2-naphthylalanine. D-Phe is the D-isomer of phenylalanine. Non-standard and D-residues resist peptidases and constrain the shape of the molecule, which is typical of the growth hormone-releasing peptide family it was derived from.

Why was it called selective?

The growth hormone-releasing peptides that preceded it, such as GHRP-6, described in 1984 [2], and GHRP-2, released growth hormone but in animal studies also raised adrenocorticotropic hormone and cortisol. In the 1998 study, Ipamorelin released growth hormone in animal models without comparable increases in those hormones, which is the sense in which it was called selective [1].

What is its regulatory status?

Ipamorelin is not approved as a medicine in the United States. As of April 2026, ipamorelin acetate appears on the FDA list of bulk drug substances that may present significant safety risks in compounding, together with GHRP-2 and GHRP-6 [3]. That list governs compounding pharmacies; it is part of the regulatory background for any reader evaluating the compound.

How is Ipamorelin identified in the laboratory?

Its naphthylalanine and phenylalanine side chains absorb ultraviolet light strongly, which makes HPLC detection straightforward. Identity is confirmed by mass spectrometry against the theoretical mass. Because D-residues have the same mass as L-residues, confirming stereochemistry requires a chiral method; standard mass spectrometry cannot distinguish them.

Frequently asked questions

Is Ipamorelin the same as GHRP-6?

No. Both act on the same receptor, but GHRP-6 is a six-residue peptide with a different sequence and a molecular weight of about 873.0 Da.

What is CJC-1295 + Ipamorelin?

It is a supplier blend of two separate peptides, usually CJC-1295 without DAC and Ipamorelin, in one vial. Each component keeps its own identity and mass.

Does FLASK list Ipamorelin?

Yes, as Ipamorelin 5 mg, and as a component of the CJC-1295 (no DAC) / Ipamorelin 5 + 5 mg blend.