The role of testosterone in diabetes and cardiovascular disease in men has been a hot topic in recent years, with a number of studies looking at the topic. Recently, we wrote about a study finding that exercise was superior to testosterone therapy at promoting blood vessel health in men with low-normal testosterone levels.
But testosterone appears to be helpful at preventing or even reversing type 2 diabetes in men with low-normal testosterone levels, according to a study published in the journal The Lancet Diabetes & Endocrinology.
Researchers at six healthcare locations in Australia recruited 1,007 men ages 50 to 74 to participate in the study, which aimed to evaluate the effects of testosterone therapy in combination with a community-based lifestyle intervention program. All participants had a waist circumference of at least 95 centimeters (37.4 inches) and a low-normal testosterone level of 6 to 14 nmol/L. They also had impaired glucose tolerance as measured by an oral glucose tolerance test (OGTT) or newly diagnosed type 2 diabetes.
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All participants took part in a lifestyle program from WW (formerly Weight watchers) focused on a healthy diet and physical activity, and they were randomly assigned to receive either a testosterone injection (1,000 milligrams) or a placebo (inactive) injection every three months for two years. Both groups were arranged to contain roughly the same number of participants overall, as well as a similar proportion of people who smoked, had a family history of type 2 diabetes, had various OGTT results or waist circumferences, and belonged to different age groups.
Testosterone’s effect on diabetes status
After two years, participants were given another OGTT to assess the effect of testosterone therapy on their diabetes status. A glucose level of 200 mg/dl or higher after two hours was used as the threshold for an OGTT result indicating diabetes, consistent with standard guidelines for diagnosing diabetes. In the placebo group, the rate of participants with diabetes based on these results was 21%, while in the testosterone group, it was only 12% — demonstrating that testosterone therapy reduced the risk of diabetes by 41%.
In the placebo group, compared with two years earlier, participants saw an average improvement in their OGTT results of 13.3 mg/dl, while the testosterone group saw a much greater average drop of 30.6 mg/dl. One important — and perhaps surprising — finding was that participants experienced an improvement in their OGTT results from testosterone therapy regardless of how high or low their testosterone was at the beginning of the study (within the range of 6 to 14 nmol/L). This would appear to show that the benefit from taking testosterone wasn’t gained simply from bringing participants closer to the normal range for testosterone, but that it was instead seen equally in those who were already close to the normal range and saw their testosterone boosted even higher.
To put the benefit from testosterone that this study found in perspective, the researchers wrote, “This effect compares favorably to that of metformin in the Diabetes Prevention Program and was accompanied by increased muscle mass, grip strength and, on average, small but sustained improvements in sexual function.” They pointed out, though, that testosterone carries certain safety risks, and that study participants overwhelmingly fell into a low risk category for them — something that may not be true for the broader population of men at high risk for type 2 diabetes.
“Although these data might inform decisions about testosterone as a pharmacotherapy for diabetes prevention, the minimum dose exposure, duration of treatment, durability of effect and long-term safety remain to be determined,” the researchers noted. “For now, we consider it premature to treat men who do not have pathological hypogonadism” — low testosterone, below 6 nmol/L — “with testosterone.”
Want to learn more about testosterone in type 2 diabetes? Read “Exercise Beats Testosterone for Blood Vessel Health in Men” and “Testosterone for Type 2 Diabetes?”