JLE

Médecine Thérapeutique / médecine de la reproduction

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Testicular function and aging Volume 9, issue 5, novembre-décembre 2007

Author
Service d’endocrinologie, Département Médecine Interne, Universitair ziekenhuis 9000 Gent

Aging in males is accompanied by a slow, steady decline of plasma testosterone levels, starting around age 40 yrs ; interindividual variations are important, however and whereas at age 75 yrs, over 40 % of men have subnormal androgen levels, many have testosterone (T) levels still in the high normal range. The clinical symptomatology of aging shows striking similarites with the symptomatology of hypogonadal young adults, raising the hypothesis that the partial androgen deficiency of the elderly might play a causal rôle in this symptomatology. The latter, however, has a multifactorial origin, aging being characterized by a decrease of almost all physiological functions which contribute to this symptomatology. It is not surprising therefore, that the correlations between (F) T levels and symptoms are at best very weak. Nevertheless, available evidence suggests that the low T levels in elderly men play a rôle in the age associated decrease in bone mineral density and in the changes in body composition with decrease of muscle mass and increase in the abdominal fat mass, although the latter may at least partially be the cause of the low T levels. The rôle of the partial hypogondism in atherosclerosis and coronary artery disease is controversial : surprisingly, low T levels appear to be associated with increased coronary artey disease (CAD)-and increased intima-media thickness of the carotid artery, whereas large prospective studies involving thousands of subjects did not reveal any correlation between T levels and CAD. As the T level required for normal sexual function is at the lower limit of the normal range, it is not surprising that no significant correlation with T levels of aging males was found. Effects of T supplementation on body composition, muscle mass and BMD are modest and most pronounced in patients with clearly hypogonadal basal T levels. The clinical significance of these effects is not evident as data on clinival relevant end points such as incidence of heart infarction, falls, bone fractures or mobility are not available. In the view of the multifactorial origin and aspecificity of aging symptoms, of the lack of a reliable, practical marker of androgen action and hence our ignorance of the androgen requirements of elderly males, and considering the possible serious side effects of androgen treatment (stimulation of subclinical prostatic carcinoma), androgen treatment should only be considered in males with both the clinical symptomatology suggesting androgen deficiency and unequivocal subnormal T levels.