Sermorelin (GHRH 1-29)
Sermorelin is GRF(1-29)NH2, the first 29 residues of growth hormone-releasing hormone, and is described as the shortest synthetic fragment that keeps the full biological activity of the 44-residue parent peptide; the research catalog lists it at https://onesourcepeptides.com/product/sermorelin-acetate.
The parent peptide was found in an unusual place. Guillemin et al., Science, 1982 (PMID 6812220) isolated a 44-amino-acid peptide with growth hormone-releasing activity from a human pancreatic tumor that had caused acromegaly, published its full sequence, and showed that the synthetic replicate had full biological activity in vitro and in vivo, specifically stimulating growth hormone secretion. The tumor peptide matched the activity of the hypothalamic releasing factor that had resisted characterization for years.
Sermorelin is the trimmed version of that sequence. The review by Prakash and Goa, BioDrugs, 1999 (PMID 18031173) describes it as a 29-amino-acid analogue of GHRH and the shortest synthetic peptide with the full biological activity of the native hormone, acting specifically on growth hormone release from the anterior pituitary. That compact 1-29 core became the scaffold for later analog chemistry.
The N-terminus turned out to be the tuning knob. In rat studies, Coy et al., Journal of Medicinal Chemistry, 1985 (PMID 3918170) reported that D-amino acid substitutions at positions 1, 2 or 3 of GRF(1-29)NH2 sharply increased growth hormone-releasing activity, with [D-Ala2]GRF(1-29)NH2 about 51 times as active as the parent 29-residue peptide, while D-substitutions at positions 6 and 7 left the analogs virtually inactive. Related notes cover CJC-1295, Ipamorelin and CJC-1295 (no DAC) with Ipamorelin, and lot identity belongs on the certificate of analysis for the vial in hand (see Are research peptides third-party tested?). Sermorelin on the catalog is laboratory research supply only. This note summarizes published biochemical and animal research and is not dosing, reconstitution, or human-use guidance.