June 26, 2012 (Houston, Texas) — Prediabetic, overweight men with hypogonadism show improvements in testosterone levels after lifestyle modifications consisting of calorie and fat reductions and exercise, according to research presented here at ENDO 2012: The Endocrine Society 94th Annual Meeting.
Researchers evaluated 891 middle-aged men with impaired glucose tolerance and low testosterone levels who undertook a 1-year lifestyle modification program involving 150 minutes per week of exercise and calorie and fat reductions in their diets.
Participants had a nearly 50% increase in testosterone levels, researchers announced.
The men had participated in the now-complete Diabetes Prevention Program study, which showed that weight loss could help people at high risk for type 2 diabetes delay or even prevent onset of the disease.
Because obesity and type 2 diabetes are linked with low testosterone levels in men, the study also offered an opportunity to evaluate the effect of such changes on testosterone levels. Men with a known diagnosis of hypogonadism or who were taking medications that could interfere with testosterone levels were excluded from the study.
For the study, men with an average age of 54 years were randomly assigned into 3 groups: 293 were assigned to the diet and exercise lifestyle modification, 305 received the diabetes drug metformin, and 293 received placebo pills. At baseline, their mean body mass index was 31.9 kg/m2, and there were no significant differences in mean testosterone levels between the groups.
At baseline, 23.7% of men in all 3 groups had hypogonadal testosterone levels, defined as less than 300 ng/dL.
After 12 months of follow-up, the investigators found no significant differences in testosterone levels in the 3 groups as a whole (407 ± 5 ng/dL at baseline vs 417 ± 5 ng/dL at 12 months).
However, men in the diet and exercise lifestyle modification group showed a 15% increase in testosterone levels compared with baseline (417 ± 8 ng/dL vs 460 ± 7 ng/dL; P < .0001). There were no changes in luteinizing hormone (LH), which is involved in Leydig cell production of testosterone levels (3.1 ± 0.1 IU/L vs 3.1 ± 0.1 IU/L). The other 2 groups had no significant changes in testosterone levels.
By the 12-month follow-up, the overall prevalence of hypogonadal testosterone levels in the lifestyle modification group decreased from 20.4% to 11.1% (P < .05), representing about a 46% decrease. It was essentially unchanged in the metformin group (24.8% vs 23.8%) and in the placebo group (25.6% vs 24.6%).
The men in the lifestyle modification group had a reduction in body weight of about 17 pounds (7.8 kg) over the course of the study, which was greater than in the metformin group (−7.8 vs −2.8 kg; P < .0001).
The lifestyle modification group's decrease in insulin sensitivity (homeostatic model assessment) was also greater than that in the metformin group (decrease from 7.0 ± 0.3 to 5.2 ± 0.2 with lifestyle modification vs from 7.2 ± 0.2 to 6.0 ± 0.3 with metformin).
Correlations were observed between testosterone levels and changes in body weight (r, −0.32; P < .0001), waist circumference (r, −0.13; P = .001), and homeostasis model assessment-estimated insulin resistance (r, −0.13; P < .0001).
No relationship was seen between the change in testosterone level and physical activity.
"As many as 1 in 4 of this male Diabetes Prevention Program cohort with impaired glucose tolerance has low testosterone levels," the authors noted.
"Lifestyle modification increases endogenous testosterone levels and reduces the prevalence of hypogonadism by 46%."
The authors suggest that "an absence of an increase in LH suggests that enhanced Leydig cell responsiveness underlies the increase in testosterone."
The study is significant, according to session moderator David J. Handelsman, MD, professor of reproductive endocrinology and andrology at the University of Sydney, Australia.
"This is a relatively large, randomized controlled study, so that elevates it into the realm of important work," said Dr. Handelsman.
"The findings show modest but positive effects on blood testosterone of weight loss in men with diabesity who otherwise have lower blood testosterone levels than lean men of same age."
Although noting that the study reinforces existing knowledge of the effect obesity has on blood testosterone levels, and that reversing the excesses weight improves the effect, Dr. Handelsman cautioned that the remedy is not testosterone treatment.
"It is important to state clearly that the lower blood testosterone levels are not a true deficiency state; rather, they are a barometer of ill health, as opposed to a real deficiency state," he told Medscape Medical News.
"An important implication is that such men should not be treated with testosterone."
The study received research support from a Career Development Award from the American Diabetes Association that was awarded to the lead author.
ENDO 2012: The Endocrine Society 94th Annual Meeting: Abstract OR28-3. Presented June 25, 2012.
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