Summary: A new study reveals that metabolic health, particularly modest increases in blood sugar, plays a bigger role than age or testosterone in declining sexual and reproductive function in men. Researchers tracked 117 healthy men over six years, assessing hormones, semen quality, erectile function, and blood sugar.
While hormone levels and semen parameters stayed normal, elevated blood sugar correlated with reduced sperm motility and erectile performance. These findings suggest lifestyle changes and medical interventions targeting metabolic health can help preserve male sexual wellbeing as men age.
Key Facts:
- Blood Sugar Impact: Even mild increases in blood sugar levels impaired sperm motility and erectile function, despite being below diabetic thresholds.
- Testosterone Insight: Testosterone influenced libido but was not directly linked to erectile performance.
- Actionable Prevention: Maintaining metabolic health may help men sustain sexual and reproductive health well into older age.
Source: Endocrine Society
Metabolic health factors, including small increases in blood sugar, are the main drivers of change in the reproductive systems and sexual functioning of aging men, according to a study being presented Saturday at ENDO 2025, the Endocrine Society’s annual meeting in San Francisco, Calif.
“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 conclusions follow a long-term study of healthy men (without diabetes mellitus, heart disease and/or cancer) aged 18-85 that began in 2014 with 200 participants and concluded in 2020 with 117 participants.
Researchers studied progressive changes in participants’ semen and hormonal profiles, erectile functioning and metabolic health (BMI and blood sugar levels marked by the HbA1c test).
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.”
Funding: This research was conducted as part of the FAME 2.0 study.
About this metabolism and sexual health research news
Author: Colleen Williams
Source: Endocrine Society
Contact: Colleen Williams – Endocrine Society
Image: The image is credited to Neuroscience News
Original Research: The findings will be presented at ENDO2025
