Obesity, illness speed testosterone decline

NEW YORK (Reuters Health) - Gaining too much weight can accelerate the decline in testosterone levels that accompanies aging, a new study shows.

"Although hormone declines appear to be an integral aspect of the aging process, rapid declines need not be dismissed as inevitable," the researchers conclude.

Men's testosterone levels fall as they get older, which may contribute to health problems such as diabetes, loss of bone and muscle mass, and sexual dysfunction, Dr. Thomas G. Travison of New England Research Institutes in Watertown, Massachusetts and colleagues note in a report in The Journal of Clinical Endocrinology and Metabolism.

To better understand how much of the decline in testosterone over time is due to aging and how much might be related to health and lifestyle changes, the researchers looked at data for 1,667 men 40 to 70 years old followed from 1987-1989 to 2002-2004. They were able to gather data for the entire time period on 35 percent, or 584, of the men.

Sharper declines in testosterone occurred among men who developed a chronic illness during the course of the study, those who lost a spouse, those who began taking six or more medications, and those who quit smoking, the researchers found.

And adding 4 to 5 points to one's body mass index (BMI) -- a tool used to determine how fat or thin a person is -- resulted in a drop in testosterone levels similar to that seen over 10 years of aging.

On average, the men experienced a 14.5 percent drop in total testosterone levels for every decade of life and a 27 percent reduction in free testosterone, but when the researchers looked at a subset of men who were completely healthy throughout the course of the study, declines in total and free testosterone were 10.5 percent and 22.8 percent, respectively. This suggests, the researchers say, that a "substantial proportion" of testosterone decline is due to changes in health.

"These results suggest the possibility that age-related hormone decline may be decelerated through the management of health and lifestyle factors," they conclude.

SOURCE: The Journal of Clinical Endocrinology and Metabolism, February 2007.