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 presented 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 well-being in men, even as they age.”
This research was conducted as part of the FAME 2.0 study.