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.