Neuroendocrine System And Aging

JOSEPH MEITES The idea that the endocrine system is involved in aging processes is as old as the beginnings of endocrinology. The first endocrine experiment related to aging was reported by Brown-Sequard, who is usually re garded as the "father of endocrinology. " In 1889, at the age of 72 years, he reported that he had succeeded in rejuvenating himself by injections of testicular extracts from dogs and guinea pigs. Although the favorable effects observed may have been due mainly to the powers of auto suggestion, his reports created a considerable interest in endocrinology and its relation to aging, and eventually led to the use of estrogens for treating certain pre-and postmenopausal symptoms in women, and an drogens for treating some symptoms in aging men. Up to about the 1960's, the relatively few studies on endocrine-aging relationships dealt mainly with changes in weight and histological appearance of endocrine organs in aging animals and human subjects, and included a limited number of measurements of endocrine function by bioassays and chem ical (for steroids) procedures. Within these limitations, gerontological investigators were unable to establish any definite relationships between endocrine functions and aging processes, with the exception of the con nection between reproductive decline and gonadal and pituitary activity.

One of the hallmarks of aging is the decreased capacity to adapt to changes in the environment. In a constant, controlled environment, it is often difficult to distin guish the functioning of the young organism from that of the old. However, when stresses are applied-temperature stresses, dietary stresses, infection, emotional stresses-the differences are more apparent. Frequently, the response ofthe old is delayed and may never reach the same mag'nitude as the young. These responses, in most cases, are mediated by the neuroendocrine system, which communicates via hormones, neurotransmitters, and related substances. Thus, it is important to understand the age-related changes that take place in the secretion and act ion of these substances and how these changes relate to the well-being of the whole organism. Indeed, the "neuroendocrine theory of aging" proposes that almost all of the characteristics of aging can be accounted for by dysfunction of the neuroendocrine system. A book on endocrine function and aging is particularly relevant at this time. With the advent of the techniques of molecular biology, there has bee~ an explo sion of knowledge concerning hormone secretion and action. Hormones, pro hormones, hormone receptors, and "second messenger" mediators rapidly are being cloned and sequenced. Such knowledge gives us important insights into the molecular workings of these substances as well as into the genetic hasis of endo crine dysfunction. These new tools are now being applied to the problem of age related changes in endocrine function.

It is the purpose of this volume to present a representative sampling of those neural and hormonal studies which have been the focus of the most intense interest in the recent gerontological research. To this end we have been fortunate to enlist the aid of some of the most competent and innovative investigators in the field. More than this, however, an attempt has been made to provide detailed methodological as well as theoretical evaluation for the areas considered. It is our hope that those researchers interested in this area of regulation during aging will be able to utilize the information contained herein as a basis both for critical analysis as well as for the designing and execution of further experiments in this more important area.

Endocrinology of Aging: Clinical Aspects in Diagrams and Images presents chapters in a way that allows the reader to incorporate concepts and complex facts in a visual way. As the global population becomes older, the need for a deeper understanding of geriatric pathology increases, and with it, there becomes a greater need to access educational resources on the endocrinology and metabolism of aging. According to the United Nations, the number of people aged 60 years or over in the world is projected to be 1.4 billion in 2030 and 2.1 billion in 2050, hence this is a timely resource. Divided according to specific endocrine and metabolic systems, providing evidence-based content Addresses physiological changes that alter the pathophysiology of the clinical picture Considers the patient transitioning from young adult to elderly, discussing endocrinological challenges to discern physiology from pathology Focuses on age as an essential factor for diagnostic and endocrine management