Low levels of testosterone are a factor in the aetiology of common ailments of elderly men such as the metabolic syndrome and osteoporosis, and the central role of testosterone in erectile dysfunction is increasingly recognised
Aksam A Yassin
MD PhD EdD FEBU
Institute of Urology &
Ageing can be viewed as a time-related functional decline of health into the frailty of old age, with an ever-increasing vulnerability to disease and eventually to death. Among the many processes of ageing, endocrine changes are relatively easy to identify and quantify. The first reports on an age-related decline of testosterone were by Werner (1939) and by Heller & Myers (1944), and about 10 years later McGavack drew a close parallel with the female menopause. The male climacteric ‘strikes at the core of what it is to be a man … his youthful sexual drive and performance and includes such symptoms as hot flashes, depression, insomnia, mood swings, irritability, impotence, decreased libido, weakness, lethargy and loss of bone mass.’ Terms like male menopause and male climacterium, or andropause, were used. It has, however, become clear that levels of testosterone do, indeed, show an age-related decline but that the characteristics of this age-related decline of testosterone are so fundamentally different from the menopause that drawing parallels generates more confusion than clarity. In men, testosterone production is affected in a slowly progressive way as part of the normal ageing process. It starts after the fourth decade of life, but it will rarely manifest in men under the age of 50 years and becomes usually only quantitatively significant in men over 60 years of age. Disease is a strong predictor of the age-related decline of plasma testosterone.[5-7] It has been argued that lifestyle changes (reduction/prevention of obesity) may decelerate the age-related decline of plasma testosterone.
Low testosterone induces disease
So, while it is clear that disease, and in particular features of the metabolic syndrome, suppress circulating testosterone levels, it has also been documented that low testosterone induces the metabolic syndrome,[9,10] dramatically demonstrated by findings in men with prostate cancer who undergo androgen ablation therapy.[11-13] A recent study showed convincingly that acute androgen deprivation reduces insulin sensitivity in young men. Very well documented is that androgen deprivation leads to osteoporosis and increases bone fractures. So, it is evident that low levels of testosterone are a factor in the aetiology of common ailments of elderly men such as the metabolic syndrome and osteoporosis.
Triad of cardiovascular disease, visceral obesity and erectile dysfunction
Cardiovascular disease, (visceral) obesity, erectile dysfunction and hypogonadism occur frequently in ageing men. Until recently they were viewed as more or less independent entities of the ageing male, usually treated by various medical specialties. With a more integrative approach to the health situation of the ageing male, these conditions appear closely interrelated in their aetiology, diagnostic strategy and treatment. Treatment of one of the components will positively impact on the others. Most ageing men are inclined to view the above conditions as inevitable occurrences at advancing age and do not readily seek medical consultation. The complaint that may motivate them to seek medical advice is erectile dysfunction. Appropriate treatment of sexual dysfunction in elderly men will imply treatment of the other conditions mentioned above, which are aetiologically closely interrelated to the complaint. Low testosterone levels predict the development of the metabolic syndrome. Testosterone administration to men with lower-than-normal plasma testosterone levels will positively influence both erectile function and the metabolic syndrome.
Testosterone and erectile (dys)function
Over the last few years there has been a renewed interest in the role of testosterone in male (patho)physiology and, more particularly, in a better definition of the place of testosterone in erectile dysfunction (ED). Recent studies provide convincing evidence that there is a powerful effect of testosterone on the anatomical and physiological substrate of penile erection. Furthermore, it has become clear that testosterone is not simply one of the many factors playing a role in erectile (dys)function. Indeed, circulating levels of testosterone are closely related to manifestations of other aetiological factors in ED, such as atherosclerotic disease and diabetes. Conversely, the latter are correlated with lower than-normal testosterone levels. Therefore, the central role of testosterone in erectile (dys)function is increasingly recognised.
Erectile potency is physiologically a complex interaction of vascular, neural, metabolic, endocrine and, last but not least, psychological factors. Erectile difficulties often provide a window into the presence of pathology in these areas. Rather than a disease in itself, ED is, particularly in elderly men who have enjoyed normal sexual functions earlier in life, a manifestation of pathologies of the biological systems involved in erectile function. But the advent of successful treatment modalities of erectile difficulties, such as the phosphodiesterase type 5 (PDE5) inhibitors, has led to a concept of erectile failure as an entity in itself rather than an expression of underlying pathology of its constituents. In other words, it has opened the door to viewing diagnosis and treatment of underlying pathology of erectile failure as redundant. But many men discontinue PDE5 inhibitors, which leads to a better definition of their ED and renewed interest in the role of testosterone. Testosterone appears to have profound effects on tissues of the penis involved in the mechanism of erection, and testosterone deficiency impairs the anatomical and physiological substrate of erectile capacity. It has been shown that the full therapeutic potential of PDE5 inhibitors will only become manifest in a eugonadal state.
The vulnerable health status usually preceding theonset of overt disability is often referred to as frailty. Many elements of frailty are related to the neurological system, metabolism, joints, bones and muscles. Central to frailty is the dramatic decline in muscle mass and strength with ageing. Therefore, sarcopenia seems to be the major determinant of frailty. Several components of the frailty syndrome are related to the physiological actions of testosterone. Testosterone has effects on psychological functioning. Testosterone (or its aromatisation product, oestradiol) is required for maintenance of bone mineral density. Testosterone stimulates red blood cell formation. Testosterone has a profound effect on body composition. A significant characteristic of ageing and a factor in frailty is the loss of muscle mass and the increase in fat mass. Androgens promote differentiation of mesenchymal multipotent cells into the myogenic lineage and inhibit their adipogenic differentiation, thus reversing the development of a downward spiral of loss of muscle mass and increase of fat mass. Skeletal muscles of older men are as responsive to the anabolic effects of testosterone as those of younger men, indicating that age as such should not be an impediment to elderly men benefiting from the anabolic effects of testosterone. So, while frailty is obviously a complex syndrome, some elements are androgen-associated and these may improve in men with subnormal testosterone levels.
Decrease of bone mineral density
With an increasing longevity, maintenance of good health is pivotal for independent living of older people. Osteoporotic fractures are a crippling occurrence in their lives and are an obvious impediment for most of the activities of daily living. Osteoporotic fractures have long been regarded as a female ailment, but with increasing longevity of men it appears that incidence and prevalence of osteoporotic fractures is not very different from the female rate, be it approximately 10 years later in the lives of men when their general health is deteriorating. A multitude of factors determine bone strength: genetic, nutritional (calcium), vitamin D (both nutritional or exposure to sunlight), physical activity and hormonal factors. Hormonal factors are significant throughout life from puberty onwards. In adolescence they are indispensable for the formation of peak bone mass. Throughout life sex steroids maintain bone formation. Surprisingly, in men oestrogens appear more significant for development of peak bone mass and maintenance of bone mineral density than androgens. In men oestrogens are derived from androgens and levels of oestrogens and androgens are strongly interrelated. Adequate androgen levels imply adequate oestrogen levels.
Professional organisations recognise that androgen deficiency in the ageing male should receive due interest and debate, not least because the demographics clearly demonstrate the increasing percentage of the population in the older age groups.[22,23] Whether older hypogonadal men will benefit from testosterone treatment and what will be the risks associated with such intervention can only be resolved by sufficiently powered studies. In the views of a number of professional bodies, these studies are timely since studies in the past decade have produced evidence of the benefit of androgen treatment on multiple target organs of hypogonadal men, and recent studies show short-term beneficial effects of testosterone in older men that are similar to those in younger men. Long-term data on the effects of testosterone treatment in the older population are limited, and specifically data on the risks of prostate and cardiovascular disease are needed. A diagnosis of androgen deficiency should be based on consistent symptoms and signs and unequivocally low serum testosterone levels.
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