Ipamorelin vs Sermorelin: Two Receptor Targets Compared
Ipamorelin and sermorelin are often mentioned together because both are studied in growth hormone research, but they act on different receptors and are very different molecules. Ipamorelin is a five-residue ghrelin-receptor agonist; sermorelin is the 29-residue active fragment of growth hormone-releasing hormone. This post compares their structures, sizes and how each is checked in the lab.
Research blog: general laboratory-science and literature context. Not medical advice. Sealed Peptides materials are for laboratory research use only, and are not for human or veterinary use.
Two different receptors
Ipamorelin belongs to the growth hormone secretagogue family. It binds the ghrelin receptor (GHS-R1a), the same receptor as the stomach-derived hormone ghrelin. It was described in 1998 and is noted in the literature for its selectivity within that family.
Sermorelin is GHRH(1-29)-NH2, the first 29 residues of growth hormone-releasing hormone, which carry the parent hormone's activity at the GHRH receptor. Because the two act at separate receptors, papers often study them as distinct pathways.
Sequence and size at a glance
- Ipamorelin: Aib-His-D-2Nal-D-Phe-Lys-NH2, listed molecular weight 711.9 Da. It contains unnatural residues (Aib, D-2-naphthylalanine) and is C-amidated.
- Sermorelin: the natural 29-residue GHRH(1-29) sequence with a C-terminal amide, listed molecular weight about 3358 Da.
- Difference in scale: sermorelin is nearly five times heavier, which changes how each behaves on HPLC and in solution.
Where CJC-1295 fits
CJC-1295 is a modified GHRH(1-29) analog, so chemically it is a relative of sermorelin, not of ipamorelin. Pairing a GHRH-receptor peptide with a ghrelin-receptor peptide is why combinations such as the CJC-1295 / Ipamorelin blend appear in research catalogs. The CJC-1295 with vs without DAC post covers that analog in detail.
Checking each one in the lab
Both are checked by Mass spectrometry for identity and HPLC for purity. Sermorelin, at 29 residues, often shows several charge states in electrospray MS, while ipamorelin usually appears as one or two simple ions.
Sermorelin contains methionine, so a peak 16 Da heavier than expected points to Oxidation. Ipamorelin has no methionine or cysteine.
Handling notes
Both are stored sealed and frozen as lyophilized powders. For concentration arithmetic, the molarity calculator converts mass to moles with each listed molecular weight.
Terms used in this guide
Related tools and guides
For laboratory research use only. Not for human or veterinary use. This post is general chemistry and literature context and does not describe or endorse any use of Sealed Peptides products.
