We sought to determine the role of sex hormone-binding globulin in patients with male infertility.Materials and Methods:
We retrospectively reviewed the records of 168 males seen at a fertility clinic from 2012 to 2014 to investigate the accuracy of total testosterone in the biochemical diagnosis of hypogonadism using calculated bioavailable testosterone as the reference value. We used multivariable analysis to assess sex hormone-binding globulin as an independent predictor of infertility.Results:
Computations using calculated bioavailable testosterone as a standard in the measurement of definitive biochemical hypogonadism (less than 156 ng/dl) revealed 81% sensitivity, 83% specificity, 81% positive predictive value and 82% negative predictive value for diagnosing hypogonadism with total testosterone alone. Of the 90 men with total testosterone greater than 300 ng/dl, 20% had low bioavailable testosterone less than 156 ng/dl, 52% had borderline low bioavailable testosterone less than 210 ng/dl and only 48% could be considered biochemically eugonadal according to calculated bioavailable testosterone. Of the 80 patients with total testosterone less than 300 ng/dl, 19% had free testosterone levels greater than 6.5 ng/dl and, thus, could be considered to be eugonadal. By a magnitude similar to that of follicle-stimulating hormone, sex hormone-binding globulin independently predicted decreased sperm concentration (p = 0.0027) and motility (p = 0.0447). After excluding men with azoospermia, only sex hormone-binding globulin levels differed significantly in classically hypogonadal men (group 1—total testosterone less than 300 ng/dl) and those missed but hypogonadal (group 2—calculated bioavailable testosterone less than 210 ng/dl) (p = 0.0001). At a more stringent cutoff of calculated bioavailable testosterone less than 156 ng/dl, sperm motility was significantly different for groups 1 and 2 (p = 0.014).Conclusions:
Adding sex hormone-binding globulin to total testosterone serum testing facilitates more accurate diagnosis with free testosterone and calculated bioavailable testosterone, and clinical implications of decreased semen parameters to a magnitude similar to that of follicle-stimulating hormone. This warrants further study of the role of sex hormone-binding globulin in male infertility.