ReviewSteroid secretion in healthy aging
Introduction
In most countries, life expectancy is continuously increasing and the population of older individuals is growing rapidly. Currently, more than 900 million people worldwide are aged 60 and above, and this number is expected to grow by more than 50% between 2015 and 2050 (United Nations, 2015). Nowadays, people spend considerably more time as older adults as compared to previous generations. Although this represents an overall positive trend, longer life does not necessarily mean more time in good health. In fact, the rising life expectancy has led to an increase in the number of people with one or more chronic conditions such as dementia, cardiovascular disease or diabetes (Beard et al., 2016). Besides an impaired quality of life, the consequences of this demographic change include dramatically rising healthcare costs for governments and societies, posing huge financial challenges for the upcoming generations. Therefore, successful aging, which refers to the increase in time spent in good health with higher age, has become a global healthcare priority (Hung et al., 2010).
Aging is caused by an accumulation of flaws in molecules and cells, with effects on their integrity and function often resulting in functional and morphological frailty. The study of aging is complex due to the great interindividual variability in the manifestation of its biological effects. As a consequence, each person ages differently (Masoro and Austad, 2010). It is therefore important to identify markers which provide insights into the age-related changes in body functions and the underlying morphology. Lengths of telomeres, epigenetic patterns, or hormones represent markers of aging. Longevity studies show clear differences in life expectancy between men and women, which stem particularly from endocrine factors (Gems, 2014). Regarding endocrine alterations with age, the hypothalamic-pituitary-gonadal (HPG) and the hypothalamic-pituitary-adrenal (HPA) axes (steroids), as well as the interplay between the axes, have an impact on central and peripheral tissues with implications for physical and mental functioning. Healthy aging markers and geroprotective interventions have been derived from endocrine studies in healthy older individuals. However, most studies examined steroid hormones with regard to pathological aging and clinical states such as depression, anxiety, dementia and sexual dysfunction (Amanatkar and Chibnall, 2014; Lupien et al., 1999; Pluchino et al., 2015). Only a small number of studies have addressed steroid hormones in healthy older men and women, providing first evidence of an association between specific hormone constellations and healthy aging (e.g. Walther et al., 2017). Such studies are highly relevant for interventions aiming to prolong healthy years in aging people.
In the following, we propose dimensions of healthy aging derived from the literature. Along these dimensions, we provide an overview of age-related steroid changes and their underlying biological mechanisms, and summarize consequences in important areas of life for older women and men. Moreover, we outline potential intervention and prevention strategies to counter age-related steroid hormone alterations.
Section snippets
Healthy aging
The concept of healthy aging reaches beyond the avoidance of disease and disability (Rowe and Kahn, 1987). Rather, healthy aging is defined by the feeling and experience of physical and mental functioning (Kuh et al., 2013). Physical and mental adaptations to changes over the life course, and the maintenance of well-being, represent pivotal challenges in healthy aging (Karlamangla et al., 2002; Kuh et al., 2013; Martin and Martin, 2002; Scholz et al., 2015). The physical, mental and well-being
Age-related steroid hormone alterations and their underlying biological mechanisms
Over the last 30 years, research on successful aging has increasingly focused on age-related hormonal changes and their consequences for physical health, mental health, and subjective well-being. Different age-related patterns of sex steroid changes emerge in women and men, whereas glucocorticoids show more comparable aged-related changes in men and women.
Steroid hormones as markers of body composition in women
The body composition of premenopausal women is characterized by subcutaneous body fat and a gynoid (pear-like) body shape, whereas postmenopausal women show an increased accumulation of body fat in visceral depots, resulting in a more central or android (apple-like) shape (Arner et al., 1991). Moreover, muscle strength, muscle mass (Messier et al., 2011) and BMD decline with age and from pre- to postmenopause (Seifert-Klauss et al., 2012). This change in body composition, and especially the
Future directions
Middle-aged and older men and women should be provided with information on healthy lifestyles in order to counteract the age-related hormonal changes and at best prevent chronic conditions. Moreover, besides their family doctor, older individuals should have access to endocrinologists, psychiatrists, and psychotherapists in order to seek support if needed. In individual cases, hormone replacement can help to overcome the age-related steroid hormone alterations and restore levels that enable
Funding
This research was funded by the Dynamics of Healthy Aging Research Priority Program (URPP) of the University of Zurich.
Declarations of interest
None.
Acknowledgements
We warmly thank Tara von Grebel (Central Informatics, University of Zurich) for creating the artwork and Sarah Mannion for proofreading. The authors declare no competing interests.
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