Slight rises in blood sugar—not aging or testosterone levels—may be the biggest threat to men’s sexual health as they get older, new research suggests.
Scientists found that even small metabolic changes, such as mildly high blood sugar, can hurt sexual function more than age or hormone levels. The study was presented at ENDO 2025, the Endocrine Society’s annual meeting in San Francisco.
“Men often blame age or testosterone for sexual health problems,” said Dr. Michael Zitzmann, a professor at University Hospital in Muenster, Germany. “But our research shows that subtle increases in blood sugar and other metabolic issues are more closely tied to these changes.”
A Six-Year Study of Healthy Men
The study followed healthy men, aged 18 to 85, from 2014 to 2020. At the start, 200 men participated. By the end, 117 remained in the study. None had diabetes, heart disease, or cancer.
Researchers tracked the men’s sperm quality, hormone levels, and sexual health. They also looked at their metabolic health using body mass index (BMI) and a standard blood sugar test known as HbA1c.
Over time, most hormone and sperm levels remained normal. But even men whose blood sugar was slightly elevated—still below the diabetes cutoff of 6.5%—showed a clear drop in sperm movement and erectile function.
Blood Sugar, Not Testosterone, Affects Erections
Interestingly, testosterone did not directly impact erectile ability. However, it was linked to men’s sex drive.
Dr. Zitzmann said the findings offer hope. “This means men can take action. By managing blood sugar and improving metabolic health, they may preserve sexual and reproductive function with age.”
A Path Toward Better Sexual Health
The study, part of the FAME 2.0 project, suggests doctors should focus more on metabolic health—not just hormones—when helping men with sexual concerns.
“We now know that improving lifestyle and medical care can help aging men maintain their sexual well-being,” said Zitzmann.
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