Cortisol: Circadian Rhythm and Response to a Stressor

Cortisol is the primary hormone of the limbic-hypothalamic-pituitary-adrenal system. Cortisol is essential to maintain homeostasis. Review and research literature obtained from databases (psychology, medicine, and nursing) and reference lists are the basis for this review. This paper includes a narrative review of the circadian rhythm of cortisol and the cortisol response to a stressor in newborns and infants. Moreover, this paper includes a review of research in which cortisol was an indicator of clinical intervention efficacy. Finally, implications for nursing research are discussed. An appropriate cortisol response to a homeostatic threat is essential to health. Anand et al found an association between high cortisol levels during and after cardiac surgery and high postoperative mortality among neonates. Anand et al proposed that extreme stress responses led to extreme catabolism that contributed to high mortality. On the other hand, an inadequate (low) cortisol response was associated with mortality from sepsis in term newborns and hypotension in sick preterm infants. Reactivity (responsivity) and regulation maintain a balance that promotes homeostasis, yet limits catabolic consequences of stress system activation. Reactivity activates and maintains a stress response; regulation promotes a steady state (circadian rhythm) and modulates a stress response.Gunnar and Davis caution that reactivity and regulation processes vary for each stress-sensitive system. For example, nonnutritive sucking regulates the behavioral stress response (eg, crying), but has little influence on the physiological stress response (eg, cortisol