Age-Related Testosterone Decline and Metabolic Determinants in 27,687 Korean Men Aged ≥40 Years: A Nationwide Population-Based Study.

PURPOSE: This study aimed to investigate age-related changes in serum testosterone levels and their associations with metabolic factors in a large, population-based cohort of Korean men. Although the age-related decline in testosterone has been established in Western populations, large-scale data in Asian men remain limited. Understanding regional differences is important for defining testosterone reference thresholds and associated health risks.

MATERIALS AND

METHODS

Data from 27,687 men aged ≥40 years who underwent routine health examinations at 20 hospitals across South Korea (2015-2024) were retrospectively analyzed. Clinical parameters included age, body mass index (BMI), fasting glucose, lipid profile, and prostate-specific antigen (PSA). Men receiving testosterone therapy or medications affecting androgen metabolism, or with a history of orchiectomy, chemotherapy, or testicular radiation, were excluded. Serum testosterone was measured from morning samples using chemiluminescent immunoassay, and biochemical hypogonadism was defined as total testosterone <2.5 ng/mL. Age-related trends were examined using ANOVA, and multivariable linear regression identified associations with metabolic variables.

RESULTS

The mean testosterone level was 4.8±1.8 ng/mL, showing a significant linear decline of approximately 0.021 ng/mL per year (p<0.001). The prevalence of biochemical hypogonadism increased from 5.5% (40-49 years) to 11.6% (≥70 years). In multivariable analysis, higher BMI, fasting glucose, and triglyceride levels were independently associated with lower testosterone, while PSA, high-density lipoprotein, and low-density lipoprotein were not significant.

CONCLUSIONS

This large nationwide study demonstrates a negative association between serum testosterone levels and age among Korean men. Obesity, hyperglycemia, and hypertriglyceridemia were additional contributors to reduced testosterone levels. Regular hormonal assessment and metabolic risk management are recommended for early detection and prevention of testosterone deficiency. Longitudinal studies are needed to clarify causal pathways and long-term outcomes.