Book Review

Endocrinology of Aging

N Engl J Med 2000; 342:1682-1683June 1, 2000

Article

Endocrinology of Aging
(Contemporary Endocrinology. No. 20.) Edited by John E. Morley and Lucretia van den Berg. 270 pp., illustrated. Totowa, N.J., Humana Press, 2000. $99.50 ISBN: 0-89603-756-8

Medical, social, and public health advances have dramatically increased the average age of the human population in many parts of the world. One consequence of these advances is the increasing proportion of elderly persons in Western societies. Not only are the elderly more numerous as a segment of society, but also more of the persons who are living longer are enjoying relatively good health. These points have important implications for public policy, but they also create new challenges with respect to understanding the biology of advanced age. The natural attributes of aging, such as menopause and declining bone mass, which were formerly of less concern because when life spans were shorter their complications were not fully expressed, have become major focuses of attention. Although all organ systems are affected by aging, some parts of the endocrine system undergo age-related changes that are predictable and well defined and probably contribute to senescence of the organism. Thus, a book on the endocrinology of aging is timely and of interest to a wide audience.

This multiauthored book is heterogeneous in content and message. Many, though not all, of the endocrine systems are covered, and forays into areas not strictly endocrine in nature, such as obesity, Paget's disease, nutrition, and the sympathetic nervous system, are included. Conceptually, there are two aspects of endocrinology and aging. The first pertains to the normal changes in endocrine function with age and their effect on health. Examples are menopause and somatopause (the decline in the secretion and action of growth hormone). The second is concerned with the prevalence, diagnosis, manifestations, and treatment of endocrine diseases in the elderly, all of which may differ in older as compared with younger patients. Examples of these differences include the prevalence of type 2 diabetes mellitus and the symptoms of hyperthyroidism in the elderly.

The first aspect is of more fundamental interest with regard to gerontology; the second is of greater interest to practicing physicians. The book serves both groups, but the emphasis on one or the other concept varies from chapter to chapter. In part, this variability is explained by the presence or absence of pertinent scientific data; in part it is driven by the authors' interests and orientation. The result is somewhat uneven, ranging from philosophical and historical considerations to detailed lists of drugs available for therapy and their dosages. All these aspects can be useful and important, depending on the reader's primary interest; however, a better integration would be desirable.

The book clearly illuminates the difficulty of separating functional impairment caused by age itself from that resulting from disease and the intertwined relation between the two. This is a notorious and well-recognized problem in geriatrics. With few exceptions, such as the chapters devoted to menopause, andropause, somatopause, and declining renal function, all of which are considered attributes of normal aging, the book focuses on medical illness. The prevalence of diseases, manifestations, diagnosis, and therapy are discussed in the context of the elderly, and much practical information is imparted. In this role, the book serves well the general internist or primary care physician who wants to learn about illnesses of the elderly and their medical management.

Endocrinology of Aging proceeds from a summary of the biologic theories of aging to chapters on the growth hormone–insulin-like growth factor I axis, the stress response, thyroid disease, renal and fluid balance, bone disease, changes in gonadal function in men and women, diabetes, obesity, and nutrition, and finally to chapters on the sympathetic nervous system and hypertension. Each chapter is structured differently; some include the results of studies in animals and in vitro investigations, others focus entirely on aging in humans, and still others discuss endocrine disease in general terms, with particular emphasis on the effects in the elderly. There is very little overlap between chapters. The information given is up to date and extensively referenced. Overall, the book provides a useful overview of what is known about normal and abnormal changes in the endocrine system in the elderly, their clinical manifestations, and appropriate therapy. What is lacking is a uniform format among chapters that allows the reader to focus quickly on a topic of interest.

One would wish for a book that describes in concise form all the natural (i.e., spontaneous and disease-independent) changes that occur in the endocrine system as a function of age. This approach would allow a better definition of the contributions of hormonal changes to functional impairment associated with aging and, hence, of the therapeutic interventions that may be beneficial in healthy elderly persons. This book partially achieves this goal. However, because of the dearth of such information untainted by disease, the goal remains largely elusive. The need is evident for research into age-related endocrine changes in healthy older persons. This will require the cooperation of the elderly and organizations that represent them, as well as funding for such studies. Even under the best circumstances, defining what is normal and abnormal endocrinologic function in the elderly will remain a tall order. Is a certain amount of bone loss normal, and at what point does it become abnormal? Is the increased prevalence of carbohydrate intolerance in the elderly a normal part of decreased physical activity and altered body composition, is it a prelude to type 2 diabetes, or is it both? Endocrinology of Aging, by its very heterogeneity, aptly illustrates the continuum between health and disease and provides some practical advice on the way. I recommend it to general internists and practicing geriatricians; it may be less suitable for gerontologists interested in the fundamental aspects of aging.

Gerhard Baumann, M.D.
Northwestern University, Chicago, IL 60611