Physiology of aging: metabolic changes during the climacteric and menopausal periods.

Endocrine regulation is altered with age. Changes in hormone secretory rates, patterns of secretion, and responses to physiologic and pharmacologic stimuli have been demonstrated. Target tissue sensitivity to hormones appears to be age related and to involve hormone receptor mechanisms, enzymatic responses, and carrier proteins. The aging process reflects changes in cellular structure and metabolism that decrease the function and efficiency of tissues. Structural changes occur with age and are characterized by a loss of elastic tissue, accumulation of highly crosslinked collagen, reduction in ground substance, and an increase in a cellular fluorescent pigment called lipofuscin. These changes decrease the pliability of tissues and alter membrane permeability. Modifications in protein synthesis and enzymatic systems may predispose the aged to autoimmune and neoplastic disease. Endocrine diseases are common in the aged and often may be atypical in their presentation. Cancer is common in the elderly and may be associated with endocrine manifestations because the tumor is producing hormones. Physicians must be aware of these syndromes so that a correct diagnosis can be established, treatment instituted, and the quality of life improved. Laboratory test results in the aged must be carefully interpreted because most aged patients are taking medications that interfere with endocrine tests and also the normal range for the elderly has not been clearly established. Abnormal laboratory diagnostic tests are common in the aged and do not always imply endocrine disease. No hormone can reverse the natural process of aging; however, hormones do regulate all metabolic functions and the neuroendocrine system plays a key role in all phases of growth, maturation, and aging.