Exogenous Peptide
A peptide that originates from outside the body, whether administered as a therapeutic drug, consumed in food, or encountered in the environment. All peptide drugs, whether identical to natural hormones or entirely synthetic, are exogenous when administered to a patient.
Technical Context
When exogenous peptides are administered, the body processes them through the same proteolytic and clearance mechanisms that handle endogenous peptides. Exogenous peptides that are structurally identical to endogenous counterparts (e.g. oxytocin, vasopressin, glucagon) generally integrate into existing physiological pathways. Modified analogues must be evaluated for novel interactions — their structural alterations may produce effects not seen with the natural molecule. The distinction between endogenous and exogenous is also relevant to anti-doping regulations, where synthetic versions of endogenous peptide hormones (such as growth hormone) are prohibited in competitive sports.