Chemistry and structure

A defined 29-residue fragment that carries the whole GHRH signal

Native GHRH is 44 amino acids long, and sermorelin, its first 29, is the shortest synthetic peptide that carries its full biological activity. Several of the early trial papers write the 1-29 fragment as GHRH(1-29)-NH2. Research groups have built GHRH peptides by solid-phase synthesis, adding one protected amino acid at a time to a chain anchored on a resin, and one study made the 1-29 fragment itself from a precursor built that way, with an enzyme forming its C-terminal amide.

This unit walks the sequence, what the public record does and does not say about its structure, and the chemical weakness that sets sermorelin apart from the longer-acting analogs: in human plasma, an enzyme clips the first two residues off the full-length hormone and leaves it essentially inactive.