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December 9, 2015
“Low T” Treatment Increases Insulin Sensitivity, Reduces Fat in Diabetic Men

Buffalo, NY—Testosterone replacement therapy significantly benefits men with type 2 diabetes with low testosterone levels, according to a new study, although no declines in hemoglobin A1c were found in the 24-week trial.

That is the conclusion of the first randomized, double-blind, placebo-controlled study of testosterone treatment in type 2 diabetic men that comprehensively investigated the role of insulin resistance and inflammation, before and after treatment with testosterone. Results were published online before print recently in Diabetes Care.

“This is the first definitive evidence that testosterone is an insulin sensitizer and hence a metabolic hormone,” said senior author Paresh Dandona, MD, PhD, of the University of Buffalo.

Low testosterone levels were associated with significantly decreased insulin sensitivity, according to the researchers. When patients with low testosterone were administered a set concentration of insulin, they showed a 36% decrease in the rate at which glucose is taken up by tissues, the study points out.

Dandona and his coauthors first reported on the relationship between insulin sensitivity and testosterone in type 2 diabetic males in 2004, following up in 2010 with a study finding that 33% of males with type 2 diabetes—whether or not they were obese—and 25% of nondiabetic, obese males have low testosterone concentrations.

“We hypothesized that testosterone may be an anti-inflammatory and insulin sensitizing agent since it has been known for some time that testosterone reduces adiposity and increases skeletal muscle,” Dandona said in a University of Buffalo press release. “Our previous work has shown that obesity is associated with oxidative stress and inflammation, and inflammatory mediators are known to interfere with insulin signaling.”

For the current study, 94 men with Type 2 diabetes—44 of them with low testosterone levels who expressed significantly lower levels of insulin signaling genes and, thus, diminished insulin sensitivity—were randomized to receive a testosterone injection or a placebo every week for 24 weeks.

While no change in body weight was detected, testosterone treatment produced a reduction in total body fat of 3 kilograms while increasing muscle mass by the same amount.

“Most importantly, we saw a dramatic increase in insulin sensitivity, demonstrated by a 32% increase in the uptake of glucose by tissues in response to insulin,” Dandona said.

In this study, hemoglobin A1c (HbA1c) levels did not drop, which the study authors suggest is a necessary indicator that testosterone can help control diabetes. Noting that fasting glucose levels had diminished by 12 milligrams per deciliter, Dandona suggested that a significant improvement in HbA1c might have been detected in a longer term study.
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