Although testosterone supplementation can counter some of the effects of aging, it doesn’t appear to improve functional mobility or muscle strength, according to a new Dutch study.A research team at the University of Utrecht evaluated the effects of testosterone supplementation on the aging process in 207 healthy men, 60-80 years old, with testosterone levels in the low to low-normal range (<13.7 nmol/L). The men were randomized to 80 mg of testosterone twice daily for six months or a matching placebo regimen. Lean body mass increased and fat mass decreased in the supplementation group, but these men showed no gains in muscle strength or functional mobility. The treated men also ended the study with greater insulin sensitivity and lower total cholesterol, but again there was a downside: lower levels of HDL. The drop in HDL ultimately led to a higher rate of metabolic syndrome in the testosterone group—from 34.5% at baseline to 47.8% six months later. This increase was greater than the 35.5% increase in metabolic syndrome seen in the placebo group, but not significantly so.Although some research suggests that testosterone can help protect cognitive function, the study revealed no such benefits. Bone mineral density was essentially unchanged as well. Other than an improvement in one hormone-related measure (toleration of stress) in the supplementation patients, quality of life did not differ significantly between the two groups. “The findings do not support a net benefit on several indicators of health and functional and cognitive performance within six months of modest testosterone supplementation in healthy men with circulating testosterone levels in the lower range,” conclude the investigators (JAMA. 2008;299: 39-52).