Endogenous

Endogenous describes processes, substances, or factors that originate from within a system rather than from outside it. The term is derived from roots meaning “within” and “to be born,” and it is used across disciplines to contrast with exogenous, produced externally.

In biology and medicine, endogenous refers to elements produced by the organism itself. Examples include endogenous hormones such as insulin and estrogen, endogenous neurotransmitters, and endogenous pyrogens that can trigger fever as part of an immune response. Endogenous processes also govern internal timing, such as circadian rhythms driven by internal clocks that persist without external cues.

Endogenous can apply to timing, regulation, and metabolism within a living system. Endogenous cycles and signals coordinate physiology, development, and homeostasis, often interacting with environmental inputs but remaining defined by internal origins and control mechanisms.

In economics, endogenous factors are those determined within a model or system, such as human capital, technological change, and institutions. Endogenous growth theory emphasizes these internal drivers as central to long-run economic expansion, in contrast to exogenous sources like external shocks or policy changes.

In geology and Earth science, endogenous processes originate within the planet, including mantle convection, volcanism, and metamorphism, which shape the interior and crust. By contrast, exogenous processes such as weathering, erosion, and sediment transport act on the surface from outside the interior. Endogenous explanations thus focus on internal mechanisms driving system behavior.