Endogenous
Originating or produced naturally within the body, as opposed to being introduced from an external source.
Many research peptides are synthetic versions of endogenous sequences — they mimic or amplify signals the body already produces naturally. BPC-157, for instance, is derived from a peptide sequence found endogenously in gastric juice, while GHRH analogs mimic the body’s own growth hormone-releasing hormone.
The endogenous nature of a compound’s template is often cited as a reason for its favorable safety profile in preclinical models, since receptors and metabolic pathways already exist to process it. However, exogenous administration of even endogenous peptides can still produce supraphysiological effects or alter feedback loops if dosed beyond natural ranges.