Small increases in blood sugar and other metabolic factors may play a larger role than previously thought in the sexual health of aging men, according to research presented Saturday at ENDO 2025, the Endocrine Society’s annual meeting.
While age and declining testosterone have traditionally been considered the primary drivers of sexual dysfunction in men, the new study suggests that modest elevations in blood sugar and metabolic shifts are more closely associated with changes in reproductive function. ”
This means that men can take steps to preserve or revive their reproductive health through lifestyle choices and targeted medical interventions,” said Michael Zitzmann, M.D., Ph.D., a professor of medicine at University Hospital in Muenster, Germany.
The findings come from a long-term study tracking 200 healthy men, ages 18 to 85, over six years. Participants were free of diabetes, heart disease, and cancer. Researchers monitored hormonal and semen profiles, erectile function, and metabolic health, including BMI and HbA1c blood sugar levels. By the study’s conclusion in 2020, 117 participants remained in the cohort.
The study revealed that while hormone levels and semen quality largely remained within normal ranges, sperm motility and erectile function declined in men with slightly elevated blood sugar levels—still below the clinical diabetes threshold of 6.5% HbA1c. Notably, testosterone levels correlated with libido but did not directly impact erectile function.
Zitzmann emphasized the practical implications of the research: “We’re hopeful this information will help doctors and patients develop effective male sexual health maintenance strategies. Our findings show it is possible to maintain sexual and reproductive wellbeing, even as men age.”
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