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

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.

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.

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.

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.