Factors influencing testicular volume in young men: results of a community-based survey

Objective To investigate the factors influencing testicular volume in young men in the community. Subjects and methods Between May and November 2001, 2700 men aged 20 years and dwelling in the community were randomly selected at a 10% sampling fraction after a sampling process by census district; 2080 men agreed to participate in the study. All volunteers underwent a standard evaluation, including a detailed medical history and physical examination. After excluding those with testicular diseases the study comprised 1792 men. Results There were significant but weak correlations between testicular volumes and height, body weight and body mass index. In a multivariate model, high environmental temperature was associated with a decreased likelihood (odds ratio, OR, 0.42; 95% confidence interval, CI, 0.29-0.60; P < 0.001) of a paired testicular volume being below the 25th percentile of all participants. The likelihood of a low paired testicular volume varied by area, with a 1.6-fold greater risk in men dwelling in large rural areas than in those in major towns. Increasing height was associated with a decreased likelihood (OR 0.60; 95% CI 0.38-0.96; P = 0.032) and low body weight with an increased likelihood of a low paired testicular volume (OR 2.54; 95% CI 1.57-4.12; P < 0.001). Conclusion These results establish that demographic and environmental factors have an effect on testicular size and suggest that body size may be important in determining testicular size in late adolescents.