For endogeny or endogeneity in other contexts, see Endogeneity and Exogeny.
Hormones are endogenous substances secreted in the body, with different biological roles and functions
Endogenous substances and processes are those that originate from within a system such as an organism, tissue, or cell.[1] The term is chiefly used in biology but also in other fields.[nb 1]
Endogenous substances and processes contrast with exogenous ones, such as drugs, which originate from outside of the organism.
Endogenous substances
Cell signalling systems such as hormone and neurotransmitter systems use endogenous substances. Endogenous substances can regulate sleep.[2]: 1 Examples of endogenous substances, and systems that use them, include
The endogenous cannabinoid system, from which the term "endocannabinoid" derives. The endocannabinoid system is important in physiology but can be modulated by phytocannabinoids originating from outside the organism, such as THC.[3]
Nitric oxide, which is an endogenous cell signalling molecule.[6] Nitric oxide was identified as the substance previously known as endothelium-derived relaxing factor (EDRF), which was known to be an endogenous substance responsible for the relaxation of vascular endothelium.
Endogenous substances typically have some physiological utility, but they can also be pathologically endogenous. For example, in auto-brewery syndrome, ethanol is endogenously produced within the digestive system through endogenous fermentation of sugars.
Endogenous effects can modulate and regulate systems, in conjunction with environmental influences.[9]: 8
Endogeny can refer to changes that originate from within a system.[9]: 8 Endogenous changes can occur in social systems and can be modelled by Marxian dialectics.[9]: 8
Orthogenesis is a similar concept to endogeny but refers to changes within separate systems that results in their evolution along similar paths.[9]: 8 The concept of orthogenesis has never been widely favored in evolutionary biology.[9]: 8
Endogenous biological clocks and biological rhythms originating from endogenous mechanisms allow forms of biochronometry.[10]: 281–282
Endogenous processes can also be pathological. For example, endogenous depression is an atypical type of depression caused by internal effects, such as cognitive and biological stressors.
^Akil, Huda; Watson, Stanley J.; Young, Elizabeth; Lewis, Michael E.; Khachaturian, Henry; Walker, J. Michael (1984). "Endogenous Opioids: Biology and Function". Annual Review of Neuroscience. 7 (1): 223–255. doi:10.1146/annurev.ne.07.030184.001255. PMID6324644.