Summary: New research shows that metabolic health—particularly modest rises in blood sugar—has a greater influence than age or testosterone on declines in men’s sexual and reproductive function. Over six years, researchers followed 117 healthy men and measured hormones, semen quality, erectile function, and blood glucose control to identify which factors best explain changes in sexual wellbeing.
The study found that, while most hormone levels and conventional semen parameters remained within normal ranges, small increases in blood sugar were linked with reduced sperm motility and poorer erectile performance. These results highlight metabolic health as a primary, modifiable contributor to male sexual and reproductive decline and suggest that lifestyle modification and targeted medical care may help preserve function as men grow older.
Key Findings
- Blood sugar impact: Even slight elevations in blood glucose—below the clinical diabetes threshold of 6.5% HbA1c—were associated with declines in sperm motility and erectile function.
- Role of testosterone: Testosterone levels correlated with libido but did not directly predict erectile performance in this group of healthy men.
- Prevention potential: Because metabolic factors are often modifiable, maintaining healthy weight, diet, and glucose control may help protect sexual and reproductive health with age.
Study details
The longitudinal investigation was conducted as part of the FAME 2.0 study. Beginning in 2014 with 200 participants, the research followed a group of healthy men aged 18 to 85 and concluded in 2020 with 117 men who completed the study. Participants had no diagnosis of diabetes, heart disease, or cancer at enrollment. Over the course of the study, researchers periodically assessed semen quality, hormone profiles (including testosterone), erectile function, body mass index (BMI), and blood glucose control as measured by HbA1c.
Over time, most measured hormone concentrations and basic semen parameters remained largely within normal limits. However, men who showed small but consistent increases in HbA1c experienced declines in sperm motility and reported worsening erectile function. The research team observed that testosterone concentrations were more closely linked to subjective measures of sexual desire rather than to objective measures of erectile function.
Clinical and practical implications
These findings shift attention toward metabolic health when addressing sexual dysfunction and reproductive decline in aging men. Because metabolic factors such as blood glucose levels and BMI can often be improved through lifestyle changes and clinical interventions, clinicians and patients have opportunities to reduce or delay deterioration in sexual health. Practical measures may include nutritional changes that support stable blood glucose, regular physical activity to improve insulin sensitivity and cardiovascular fitness, and medical evaluation of metabolic risk factors to guide individualized care.
The study’s authors emphasize that maintaining metabolic health is a proactive strategy: even modest improvements in blood sugar control and overall metabolic function may help preserve sperm quality and erectile performance as men age. The research encourages healthcare providers to consider metabolic assessment and management as part of routine sexual health care for middle-aged and older men.
Conclusions
In this long-term cohort of healthy men, modest elevations in blood sugar emerged as a stronger predictor of declines in sperm motility and erectile function than chronological age or testosterone levels. The results underline the importance of metabolic health in male sexual and reproductive wellbeing and support prevention strategies focused on glucose control, weight management, and overall metabolic fitness.
Funding and presentation
This research was conducted as part of the FAME 2.0 study and was presented at ENDO 2025, the annual meeting of the Endocrine Society.
About this metabolism and sexual health research news
Author: Colleen Williams
Source: Endocrine Society
Contact: Colleen Williams – Endocrine Society
Image credit: Neuroscience News
Original research: Findings presented at ENDO2025