HOUSTON – A decline in testosterone is not an inevitable result of aging in men, according to a large population-based, longitudinal study.
"There’s an often-spoken-about concept that there is a decrease in testosterone with increasing age in men. Some people have even gone so far as to talk about an ‘andropause,’ or sudden drop in testosterone at some particular critical point in time reached in middle age. But we showed there’s almost no change in testosterone with age. At baseline, the mean serum total testosterone was 16.2 nmol/L, and at 5 years of follow-up it was 15.6. So essentially there is no age effect," declared Dr. Gary A. Wittert, professor of medicine at the University of Adelaide (South Australia).
Dr. Gary Wittert
He is director of the ongoing longitudinal MAILES (Male Adelaide Inflammation Lifestyle Environment Study). For this analysis of testosterone trends over time, he reported on 1,382 community-dwelling MAILES participants who averaged 54 years of age at entry. None was on medications that were known to affect hormones.
Although there was no significant change in testosterone over the course of 5 years in the overall group, some men did experience a significant decline in levels. A multivariate linear regression analysis identified several potent predictors of a progressive fall in testosterone (unmarried status, being depressed at baseline and at follow-up, cardiovascular disease, obesity, and weight gain during follow-up).
"It is critical that doctors understand that declining testosterone levels are not a natural part of aging and that they are most likely due to health-related behaviors or health status itself – particularly the burden of chronic disease, obesity, and depression," he said.
Counsel patients that the most important thing they can do to maintain their manhood, "or their mojo, is to prevent obesity. I think the most important target for preventing the decline in testosterone and all its consequences is to deal with the rapidly increasing obesity epidemic and maintain the healthiest possible lifestyle," Dr. Wittert said.
Men who maintained a normal weight had no change over time in testosterone. Those who lost weight showed a modest increase in the hormone. And men who transitioned from normal weight at baseline to obesity at follow-up showed a reduction in testosterone with no compensatory increase in luteinizing hormone levels, suggesting a central failure at the hypothalamic/pituitary level, he continued.
Dr. Wittert is the principal investigator in a six-center Australian prospective randomized trial that’s looking at whether testosterone replacement therapy plus a lifestyle intervention prevents progression from prediabetes to diabetes in hypogonadal men older than age 50 who are at increased risk. The control arm in the study, which is just beginning enrollment, will receive placebo plus the lifestyle intervention.
One of the hypotheses being tested is whether testosterone replacement improves motivation to engage in lifestyle change, a benefit that Dr. Wittert and others have observed anecdotally. Secondary end points in the study include the effect of testosterone replacement on cardiovascular disease risk and on bone health.
Testosterone levels tended to decline in smokers who quit. That’s clearly not a valid reason to continue smoking. Yet this intriguing relationship between smoking and testosterone is worthy of further investigation, in Dr. Wittert’s view.
The study is being funded by the National Health and Medical Research Council of Australia.