Throughout life, human beings undergo several hormonal changes responsible for growth and maturation. These alterations in hormone secretion include enhanced or decreased production, the latter of which is mainly observed during aging. These processes are intrinsic to human development, but may vary from individual to individual. Thus, experienced metabolic changes can alter the state of health and even trigger the development of certain pathologies.The main metabolic differences observed in newborns and children when compared to adults result from the fact that the organism is not yet fully developed. During adolescence, changes in hormone secretion occur that lead to sexual maturation. In the same way, during pregnancy, women suffer alterations in the secretion of certain hormones which allow the adaptation of their bodies to that physiological state and the normal development of the foetus. As for the elderly, a general decline of health is observed during ageing, and hormonal dysfunctions, such as the development of insulin resistance and thyroid dysfunction, frequently occur.This volume focuses on metabolic and hormonal changes during the human lifetime. Screenings best suited for each life stage, the reasons for doing them, and the diseases they allow the diagnosis of are also presented.