Inhibin B: comparison with indexes of fertility among formerly cryptorchid and control men

Infertility may be a consequence of cryptorchidism. We previously reported, using a large study cohort, that 38% of formerly bilateral cryptorchid men, 10% of unilateral cryptorchid men, and 5% of the control group were infertile. Men from this cohort donated blood and semen samples for inhibin B, FSH, LH, testosterone, free testosterone, and semen analyses. Results are reported comparing the entire group; some comparisons are based on normal or low sperm density. Data are also presented for men who had fathered children or had unsuccessfully attempted paternity. Mean (+/-SD) inhibin B levels were lower for the cryptorchid men (109 +/- 59 pg/mL) than the control men (153 +/- 60; P < 0.001), and FSH levels were higher (7.4 +/- 6.2 and 4.0 +/- 3.2; P < 0.0001). Inhibin B levels correlated with all other parameters for the cryptorchid group; however, correlations for the control group were only found with gonadotropins. Among the cryptorchid men, levels were significantly greater among men with normal sperm counts than men with low sperm counts (124 +/- 47 vs. 75 +/- 48 pg/mL; P < 0.0001). No difference was present for the control group (155 +/- 61 vs. 149 +/- 63 pg/mL). When the fertile group (based on paternity) vs. the infertile group (based on attempted paternity) were compared, significant differences were found for the cryptorchid group (117 +/- 62 vs. 73 +/- 52 pg/mL; P < 0.03), but not the control group (163 +/- 62 vs. 146 +/- 73 pg/mL). These data reveal relationships not apparent among the control group of men, which includes infertile men. Inhibin B data suggest that a larger portion of formerly cryptorchid men have compromised testicular function than indicated by paternity data. Low levels of inhibin B among individuals are an indication of diminished seminiferous tubule function and thus compromised potential for fertility. Low inhibin B levels together with elevated FSH levels and decreased sperm density are indicative of a high risk of infertility.