Incidence and risk factors of low testosterone in infertile men with normal sperm concentration

Background Current guidelines recommend endocrine evaluation for infertile men; however, those with normal sperm concentration (≥15 million/mL) may be under-referred for comprehensive assessment. This study aimed to investigate the prevalence of low testosterone in infertile men with normal sperm concentration and to determine the proportion who remain endocrinologically unevaluated. Methods A retrospective review was conducted on infertile men with initial sperm concentration ≥15 million/mL evaluated at a single tertiary center from January 2013 to December 2020. Low testosterone was defined as serum total testosterone below 300 ng/dL. Multivariate logistic regression identified independent predictors of low testosterone. Results Of 3,147 men meeting inclusion criteria, 77.2% (n=2,429) did not undergo hormonal evaluation. Endocrine assessment rates varied significantly by specialty: 100% for male infertility fellowship-trained urologists, 23.2% for general urologists, and 1.2% for gynecologists. Among 718 men who underwent hormonal testing, 24.1% had low testosterone. Multivariate logistic regression identified higher BMI (OR 1.083, 95% CI 1.031–1.136, p=0.001) and lower estradiol (OR 0.956, 95% CI 0.937–0.976, p<0.001) as independent predictors. Obese men had significantly higher odds of low testosterone compared with normal-weight men (OR 1.725, 95% CI 1.010–2.943, p=0.046). Of 66 treated men, significant testosterone increases were observed at all follow-up time points (all p ≤ 0.001), and six achieved natural pregnancy. Conclusion Over three-quarters of normozoospermic infertile men did not receive hormonal evaluation. Among those evaluated, nearly one-quarter had low testosterone, with obesity identified as an independent risk factor. These findings highlight a critical screening gap and support routine endocrine screening regardless of sperm concentration, particularly in men with metabolic risk factors such as obesity, as low testosterone represents a treatable condition that may improve fertility outcomes.