U. BUFFALO (US) — Obese adolescent boys have up to 50 percent less total testosterone than do normal-weight boys of the same age, significantly increasing the risk for impotency as adults.
“We were surprised to observe a 50 percent reduction in testosterone in this pediatric study because these obese males were young and were not diabetic,” says Paresh Dandona, professor of medicine and chief of the division of endocrinology, diabetes, and metabolism at the University at Buffalo.
“The implications of our findings are, frankly, horrendous because these boys are potentially impotent and infertile. The message is a grim one with massive epidemiological implications.”
Published online in the journal Clinical Endocrinology, the small study included boys between the ages of 14 and 20—25 boys who were obese and 25 who were lean—and was controlled for age and level of sexual maturity. Concentrations of total and free testosterone and estradiol, an estrogen hormone, were measured in morning fasting blood samples.
The researchers say the results now need to be confirmed with a larger number of subjects.
“These findings demonstrate that the effect of obesity is powerful, even in the young, and that lifestyle and nutritional intake starting in childhood have major repercussions throughout all stages of life,” Dandona says.
In addition to the reproductive consequences, the absence or low levels of testosterone that were found also will increase the tendency toward abdominal fat and reduced muscle, Dandona says, leading to insulin resistance, which contributes to diabetes.
“The good news is that we know that testosterone levels do return to normal in obese adult males who undergo gastric bypass surgery,” says Dandona. “It’s possible that levels also will return to normal through weight loss as a result of lifestyle change, although this needs to be confirmed by larger studies.”
The same authors reported in 2004 the presence of low testosterone levels, known as hypogonadism, in obese, type 2 diabetic adult males and confirmed it in 2010 in more than 2,000 obese men, both diabetic and nondiabetic. They now intend to study whether or not weight loss accomplished either through lifestyle changes or through pharmacological intervention will restore testosterone levels in obese teen males.
The research was funded by the National Institutes of Health.
Source: University at Buffalo