Stress, Hormones, and Aging

Abstract

The relationship among stress, hormones, and aging is complex and involves the interplay between three major physiological levels: molecular, cellular, and neuroendo¬crine (1). In this context, the molecular level refers to those intracellular biochemical processes directly related to the genome, such as transcription, and how gene expression is modified by age, stress, or a combination of the two. The cellular level refers to the heterogeneous cell populations within complex tissues that proliferate and/or die off during the life-span. A loss or gain of a particular cell type, or a change in the ratio of responsive to nonresponsive cells, would likely alter the organism’s response to a stressor, as a direct result of the natural aging process. The neuroendocrine level refers to the various neurotransmitter and hormonal systems that modulate a host of biological functions, including those systems preeminently involved in the organism’s response to stress. Stress can be defined as any force that changes the organism’s baseline equilibrium or homeostasis (2). Environmental factors can generically be described as “stress.” An organism’s adaptive response to stress is generally aimed at minimizing dysequilib-rium and reestablishing homeostasis. If the adaptive responses to stress are inadequate for the reestablishment of homeostasis, or are prolonged or excessive, the organism will acquire negative stress-induced consequences. Stress and changes in the stress response system can either protect against or facilitate aging. Thus, many genetic factors are responsible for the aging process, but the interplay between the organism and its external environment is clearly of paramount importance (1).