biomarker

bio·mark·er

noun \ˈbī-ō-ˌmär-kər\

Definition of BIOMARKER

: a distinctive biological or biologically derived indicator (as a biochemical metabolite in the body) of a process, event, or condition (as aging, disease, or exposure to a toxic substance) <age-related biomarkers of disease and degenerative change—Janet Raloff>