ex·og·e·nous 
(ĕk-sŏjə-nəs)
(ĕk-sŏjə-nəs)adj.
1. Originating externally: an exogenous model of economic growth.
2. Originating or produced from outside a cell, tissue, or organism: exogenous antioxidants.
[French exogène : Greek exō-, exo- + French -gène, -gen.]
ex·oge·nous·ly adv.
ex·oge·ny (-ə-mē) n.