Emerging evidence underscores that even slight elevations in blood sugar—still well below diabetic thresholds—may play a more critical role in age-related erectile dysfunction (ED) among men than previously thought, shifting the paradigm away from the traditional hormone-centric focus.
A pivotal study presented on July 13 at the Endocrine Society’s annual meeting in San Francisco tracked 200 initially healthy men, aged 18 to 85, from 2014 to 2020. Of those, 117 participants remained free from diabetes, heart disease, or cancer, allowing researchers to isolate the effects of metabolic and hormonal variables on sexual function.
Contrary to longstanding belief, testosterone levels and semen quality remained within normal ranges for most participants, even as erectile function noticeably declined. The decline was most strongly associated with modest increases in blood sugar (hemoglobin A1c or HbA1c) observed over the study period—still below the diagnostic threshold for type 2 diabetes.
Dr. Michael Zitzmann of the University Hospital in Muenster, who led the study, emphasized the importance of this finding: “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.”
While testosterone is undeniably linked with libido—men in the study with higher testosterone reported stronger sex drives—the study found no direct connection between testosterone levels and erectile function. This challenges the recent trend of using testosterone replacement therapy (TRT) as a go-to intervention for sexual aging.
With metabolic factors emerging as stronger predictors of erectile health, the findings come amid growing concern over TRT’s side effects—including cardiovascular risks—which has fueled debate about its increasing prescription.
The study revealed that, across the study period, testosterone and semen parameters stayed largely within normal limits for participants. Even subclinical increases in blood sugar (measured via HbA1c) correlated with reduced erectile function. Although testosterone levels didn’t predict erectile function, they were linked with libido, confirming their role in sexual motivation but not performance. Metabolic shifts—not hormonal decline—may be the driving factor behind midlife erectile decline, pointing to the importance of prevention. Addressing metabolic health through diet, exercise, weight control, and limiting alcohol and tobacco use may offer crucial leverage for preserving sexual health.
This study aligns with a broad body of research connecting metabolic syndrome—marked by high blood sugar, excess weight, high blood pressure, and adverse lipid profiles—with erectile dysfunction. A 2023 meta-analysis of over 12,000 men found metabolic syndrome was associated with a 2.6-fold increased risk of ED, with elevated fasting blood sugar specifically showing an odds ratio of 2.07. Analysis of national data (NHANES 2001–2004) showed men with metabolic syndrome were more than twice as likely to have ED, especially among smokers, older men, and those with abdominal obesity.
Collectively, the data highlight that metabolic components—not hormonal shifts alone—are pivotal determinants of erectile health.
For clinicians and patients, the implications are significant. Routinely checking HbA1c, fasting glucose, BMI, waist circumference, and lipid profiles in middle-aged men—even before symptoms arise—can be critical. Prioritizing interventions like exercise, balanced diet, weight management, and smoking or alcohol cessation can reverse or mitigate metabolic-driven ED. When necessary, clinicians may consider therapies that improve insulin sensitivity or support metabolic health, although more research is needed in the context of ED. Testosterone therapy should be reserved for men with clinically low testosterone and symptoms like diminished libido, fatigue, or mood disorders—not solely for erectile performance. ED should be treated as an integrated health issue—addressing metabolic, vascular, psychological, and lifestyle factors rather than focusing narrowly on hormones.
Dr. Zitzmann emphasized that the findings could revolutionize preventative strategies for men’s sexual health. “We now know that it’s in our power to retain sexual and reproductive wellbeing in men, even as they age,” he said.
Future directions include further research to establish causality and identify threshold levels of HbA1c that most strongly predict ED risk. Clinical trials testing whether improving metabolic markers can reverse ED symptoms, and public awareness campaigns framing healthy lifestyle habits as key to sexual health, may all play a role in reshaping the conversation around aging and men’s wellness.
The July 2025 study marks a fundamental shift in how erectile dysfunction is understood: not primarily as a consequence of hormone decline, but rather as a warning signal of broader metabolic dysfunction. For middle-aged and older men, monitoring blood sugar and metabolic health may be the missing key to preserving sexual vitality—not merely chasing testosterone levels. By integrating metabolic screening and lifestyle interventions into men’s health care, clinicians have a powerful opportunity to improve both sexual function and overall well-being.