Glucocorticosteroids: Stress or Anti-stress Hormones?
John C. Wingfield
Department of Zoology
University of Washington, Seattle, WA
All vertebrates organize their life history cycles around predictable changes in their environment. Superimposed on this predictable cycle are unpredictable events that often have the potential to be stressful. Over the past decade we have accumulated evidence that acute rises in circulating glucocorticosteroid secretion trigger rapid changes in physiology and behavior that may ameliorate the potential for stress in the face of an unpredictable perturbation. It appears that a facultative life history stage (the emergency life history stage - ELHS) may be orchestrated by glucocorticosteroids in conjunction with several peptides associated with the hypothalamo-pituitary- adrenal axis. After the perturbation passes glucocorticosteroid secretion declines and the individual can return to its normal life history stage. We have extensive experimental evidence for such roles of glucocorticosteroids and several field studies indicate that glucocorticosteroid levels in blood are elevated when individuals are in an ELHS. Recent evidence suggests that rises in glucocorticosteroid secretion can occur rapidly in response to a perturbation of the environment and that corticosteroid-binding proteins in blood may also be involved in determining when the ELHS is triggered. In sum these data suggest that chronic stress resulting from prolonged high levels of circulating glucocorticosteroids can be avoided by expressing the ELHS. In other words, acute rises in glucocorticosteroids following perturbations of the environment may actually avoid chronic stress and serve primarily as "anti-stress" hormones.