New research flips the script on male aging: it’s not just age or testosterone driving sexual decline, but subtle rises in blood sugar.
A long-term study of healthy men shows that even non-diabetic glucose levels can slow sperm, weaken erections, and reduce libido. The findings suggest that controlling blood sugar — not just hormone levels — could be key to preserving sexual and reproductive health in aging men.
Blood Sugar Drives Male Reproductive Changes
Changes in reproductive and sexual health among aging men are more strongly linked to metabolic factors, especially slight rises in blood sugar, than to age alone, according to findings shared at ENDO 2025, the Endocrine Society’s annual meeting in San Francisco, California.
“Although age and testosterone levels have long been considered an impetus for men’s declining sexual health, our research indicates that these changes more closely correlate with modest increases in blood sugar and other metabolic changes,” said Michael Zitzmann, M.D., Ph.D., professor and doctor of medicine at University Hospital in Muenster, Germany. “This means that men can take steps to preserve or revive their reproductive health with lifestyle choices and appropriate medical interventions.”
These insights are based on a multi-year study that began in 2014 and concluded in 2020, involving initially 200 healthy men (with no history of diabetes mellitus, heart disease, and/or cancer) between the ages of 18 and 85. By the end of the study, 117 participants remained. Researchers tracked gradual changes in semen quality, hormone levels, erectile function, and metabolic indicators such as body mass index (BMI) and HbA1c, a marker of blood sugar.
Subtle Sugar Rises Impact Sperm and Erections
Findings indicated that over time, hormone levels and semen parameters stayed largely within normal ranges. However, sperm movement and erectile function declined in men with minimally elevated blood sugar levels that were below the 6.5% HbA1c diabetes threshold. The study also found that while testosterone levels did not have a direct impact on erectile function, they did correlate with participants’ libido assessment.
“We’re hopeful that the information gleaned from this study will help doctors and their patients formulate effective male sexual health maintenance plans,” Zitzmann added. “We now know that it’s in our power to retain sexual and reproductive wellbeing in men, even as they age.”
This research was conducted as part of the FAME 2.0 study.
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1 Comment
I wonder how GLP-1 agonists and their like might help alleviate this?