Testosterone Therapy Lowers Diabetes Risk in Men on Lifestyle Programs

Gary Wittert, MD

New evidence appears to bolster the case that men who have low serum testosterone levels can mitigate the related risk of type 2 diabetes by undergoing testosterone treatment.

The findings build upon earlier research suggesting potential benefits to the therapy.

Low testosterone levels have been linked with an increased risk of type 2 diabetes, and men who are overweight or obese often have low testosterone. In many cases, community-based lifestyle programs are a main strategy used to help reverse the risk.

Corresponding author Gary Wittert, MD, of the South Australian Health and Medical Research Institute, and colleagues wanted to find out whether pairing such a program with testosterone injection therapy might have the effect of either mitigating diabetes risk or even reversing early diabetes.

The authors designed a two-year, randomized, double-blind, placebo controlled phase 3b trial of men ages 50-74 who were enrolled in a community-based lifestyle program developed by WW (formerly known as Weight Watchers).

The men each had a waist circumference exceeding 95 cm, serum testosterone concentrations of 14.0 nmol/L or lower (but without pathological hypogonadism), and either impaired glucose tolerance or newly diagnosed type 2 diabetes.

Of more than 19,000 men pre-screened at 6 Australian tertiary care centers, a total of 1,007 were eventually enrolled in the study, between the years 2013 and 2017. The enrollees were evenly divided between those receiving placebo (503) and those who were given an intramuscular injection of testosterone undecanoate (1000 mg). Both the placebo and the testosterone injections were given for 6 weeks, then every 3 months for the next 2 years.

The primary outcome was type 2 diabetes based on the two-hour oral glucose tolerance test (2-h OGTT) and mean change from baseline 2-h OGTT glucose, assessed by intention to treat.

After 2 years, the data showed a marked difference in the glucose test results for patients in the 2 arms of the study. Of the 413 participants in the placebo group for whom data were available, 87 (21%) had 2-h glucose levels of 11.1 mmol or higher; in the testosterone group, just 12% of patients (55 of 443 participants) met that threshold. In terms of change from glucose baseline, the mean change in the placebo group was -0.95 mmol/L and in the placebo group the mean change was -1.70 mmol/L. Those data were independent of baseline serum testosterone levels.

Wittert told HCPLive that the most likely reason for the effect of testosterone treatment is that it impacts the patient’s body composition.

“It is most likely the effect is mostly mediated by a decrease in fat mass, however an increase in muscle mass and function may also be contributing,” he said.

Wittert and colleagues added a note of caution. The study included masked monitoring of hematocrit and prostate-specific antigen to assess safety. Six (1%) patients in the placebo group and 106 (22%) of patients in the testosterone group met the trigger of hematocrit greater than 54%. The prostate-specific antigen trigger of an increase of 0.75 μg/mL was met by 87 (19%) of patients in the placebo group and 109 (23%) of patients in the testosterone group.

Wittert and colleagues concluded that the increases in hematocrit might be treatment limiting, but they said longer-term studies would be needed to better understand the durability of the treatment as well as its longterm safety.

The study, "Testosterone treatment to prevent or revert type 2 diabetes in men enrolled in a lifestyle programme (T4DM): a randomised, double-blind, placebo-controlled, 2-year, phase 3b trial," was published online in The Lancet Diabetes & Endocrinology.