Data from the Baltimore Longitudinal Study on Aging (890 men), suggested that 20% of the men over 60 years of age, 30% over 70 years, and 50% over 80 years were hypogonadal, as defined by a total testosterone level < 325 ng/dl (11.3 nmol/l), . It is widely believed that total testosterone declines 1% per year after the age of 50 years . Thus, the decline in testosterone follows a time course similar to the decline in muscle strength and muscle mass. Many individuals believe that it is the decline in testosterone over time that results in a reduction in muscle mass and muscle strength, and that by administering replacement doses of testosterone these parameters can be restored.
Morley et al.  studied 37 men aged 69-89 years old. Twenty-six of the men had a mean total testosterone level of < 272 ng/dl. They were administered 200 mg of testosterone enanthate every 2 weeks for 3 months. Alternating cases was the method used to assign subjects to treatment or placebo groups. The authors reported a nine-fold increase in bioavailable testosterone and a significant increase in right-hand muscle strength. Sih et al.  reported that 12 months of testosterone replacement (biweekly injections of 200 mg) in hypogonadal elderly men resulted in a significant increase in bilateral grip strength. Bhasin et al.  examined the effects of 10 weeks of testosterone replacement (100 mg/week) on body composition and strength in seven hypogonadal men aged 19-47 in an open-labelled non-randomised study. By day 15, serum testosterone had increased from 71.9 to 509 ng/ml. After 10 weeks, there was an 8.8 % increase in fat-free mass, an 11% increase in triceps cross-sectional area, and a 7% increase in thigh cross-sectional area. Strength on the bench press increased by 22% and that on the squat exercise by 45%. The caveat from the study of Bhasin et al.  is that these men had extremely low testosterone concentrations (mean = 71.9 ng/ml). As described above, the investigators from the Baltimore Longitudinal Study on Aging used a testosterone concentration of < 325 ng/l as the cut off for hypogonadism . Thus, because the testosterone concentration was so low in the study of Bhasin et al. , and presumably muscle mass and muscle strength were extremely low, the response of these parameters to the administration of 100 mg testosterone/week may have been greater than that seen in other investigations. Brodsky et al.  studied testosterone replacement (3 mg/kg every 2 weeks) in hypogonadal men (total testosterone < 200 ng/ml). They reported a 15% increase in fat-free mass and a 13% increase in appendicular muscle mass. Tenover  used a double-blind randomised controlled trial to study the effects of testosterone replacement (100 mg/week; 3 months) in men age 57-76
who had low or borderline low serum testosterone (< 13.9 nmol/l; 400 ng/dl). A small (3%) increase in lean body mass and no change in grip strength were reported. In an open-labelled trial without a control group, Urban et al.  administered 100 mg of testosterone per week over 4 weeks to elderly men with a serum testosterone concentration of < 480 ng/dl. Significant increases in strength in the hamstrings and quadriceps of both legs were observed. In contrast to the positive benefits observed in most studies, Snyder et al.  reported that, despite a 70% increase in testosterone concentration over 36 months in men over the age of 65 (using a testosterone patch), there was no significant improvement in muscle strength despite a significant increase in lean body mass. Thus, from these data it appears that testosterone replacement is likely an effective intervention for reversing sar-copenia. However, whether it is a better and/or safer alternative than resistance training remains to be determined.
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