Cortisol, the main stress hormone, is a marker of the body's adaptation to challenge. Physiology and regulation of cortisol are intricately related to an individual's health, both physical and psychological. In this book, the authors present current research in the physiology, regulation and health implications of cortisol. Topics include cortisol transport across biological barriers; the biophysical correlates of cortisol activity in children exposed to natural disasters; predictions of physiological disorders by accurate measurement of the cortisol to cortisone ratios; and, the relationship of cortisol to physical exercise and athletic performance.