Testicular volume (TV) is considered a good clinical marker of hormonal and spermatogenic function. Accurate reference values for TV measures in infertile and fertile men are lacking. We aimed to assess references values for TV in white-European infertile men and fertile controls. We analyzed clinical and laboratory data from 1940 (95.0%) infertile men and 102 (5.0%) fertile controls. Groups were matched by age using propensity score weighting. TV was assessed using a Prader orchidometer (PO). Circulating hormones and semen parameters were investigated in every male. Descriptive statistics, Spearman's correlation, and logistic regression models tested potential associations between PO-estimated TV values and clinical variables. Receiver operating characteristic (ROC) curves were used to find TV value cutoffs for oligoasthenoteratozoospermia (OAT) and nonobstructive azoospermia (NOA) status in infertile men. The median testicular volume was smaller in infertile than that of fertile men (15.0 ml vs 22.5 ml; P < 0.001). TV positively correlated with total testosterone, sperm concentration, and progressive sperm motility (all P ≤ 0.001) in infertile men. At multivariable logistic regression analysis, infertile status (P < 0.001) and the presence of left varicocele (P < 0.001) were associated with TV < 15 ml. Testicular volume thresholds of 15 ml and 12 ml had a good predictive ability for detecting OAT and NOA status, respectively. In conclusion, infertile men have smaller testicular volume than fertile controls. TV positively correlated with total testosterone, sperm concentration, and progressive motility in infertile men, which was not the case in the age-matched fertile counterparts.

Keywords: hypogonadism; male infertility; orchidometer; Prader; semen analysis; testicular volume

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