News release

From: Adelaide University

Long-term use of testosterone treatments may make older men stronger, but it alone is unlikely to help them in the battle against type two diabetes.

Adelaide University researchers led an Australian-based collaborative trial involving centres in Sydney, Melbourne, Perth and Brisbane, looking at the effects of testosterone treatment over four years to prevent type 2 diabetes in at risk men between the ages of 50 and 74.

This study was an extension of a previous trial involving more than 1000 men, which showed that when combined with a healthy lifestyle program, testosterone treatment resulted in a 40% reduction in diabetes after two years, compared to a placebo.

In the most recent study, a smaller group of 120 men volunteered to continue the trial, taking either the testosterone treatment or a placebo without the lifestyle program treatment, for another two years.

They found the treatment did help reduce body fat and improve muscle mass and strength, blood glucose, and sexual desire.

However, while most of these improvements occurred early on and were maintained for the duration of the study, the early benefits to blood sugar control diminished over time.

“In some older men, small benefits of testosterone did persist for up to four years,” said Adelaide University Professor Gary Wittert, Director of the Freemasons Centre for Men's Health and Wellbeing.

“However, when it came to blood sugar, the benefits were greatest early on, and by the four-year mark the proportion of men with diabetes in the testosterone treatment group increased and was similar to the placebo treatment group.”

“The most likely explanation for these findings is that testosterone is not a replacement for a healthy lifestyle and would need to be combined with a weight loss program for the best chance of preventing type two diabetes.”

The results of the study have been presented at the ENDO 2026 conference in Chicago.

Type two diabetes is a common, chronic condition linked to abdominal obesity, unhealthy diet and lack of physical activity.

More than 1.2 million Australians are living with the disease, with males more likely to be affected than females.

“Even with newer treatments for type two diabetes, like Ozempic, a healthy diet and both resistance and aerobic physical activity are necessary for the best overall health outcome,” said Professor Wittert.

“One of the important messages from this research is to routinely measure waist circumference and consider metabolic health. Optimising lifestyle related health behaviours can improve testosterone levels, reduce fat, increase muscle and improve sexual function.”