It is a modified version of the shortest fully functional fragment of GHRH, often referred to as growth hormone releasing factor (1-29) (abbreviated as GRF (1-29)), and also known by its standardized name, sermorelin.
This substitution resulted in a peptide bond between D-Ala and the 3rd amino acid in the structure aspartic acid (Asp) more able to resist rapid cleavage by the enzyme dipeptidyl peptidase-4, a cleavage which had previously led to an inactive peptide fragment.
[3][4] This successful modification prompted the further creation of analogues with additional amino acid substitutions.
Continued use of the term on public and private forums has popularized and standardized the nomenclature.
[citation needed] Modified GRF (1-29) acts to increase growth hormone production and release by binding to the growth-hormone-releasing hormone receptor (GHRHR) on cells in the anterior pituitary.