Inhibin B reference data for fertile and infertile men in Northeast America

ObjectiveTo determine normative levels of inhibin B and examine levels in relationship to FSH, sperm count, and motility in a cohort of fertile and infertile men from the Northeast United States.DesignProspective comparative study of inhibin B levels in fertile and infertile patient groups.SettingTertiary academic referral center.Patient(s)Fertile men were recruited among those presenting for elective vasectomy. Men being evaluated for infertility were also recruited within the same practice.Intervention(s)Serum collection.Main Outcome Measure(s)FSH and inhibin B levels were measured in serum samples.Result(s)A total of 55 fertile and 85 presenting for infertility evaluations were recruited. The mean serum inhibin B level was significantly higher in the fertile (138 pg/mL) than infertile group (78 pg/mL). Inhibin B levels correlated positively (R2 = 0.27) and FSH correlated negatively (R2 = 0.33) with total sperm concentration. General linear model multiple regression demonstrated that the FSH and inhibin B were equally predictive of sperm concentration.Conclusion(s)Inhibin B levels in fertile men and infertile men in Northeast America were similar but not identical to those reported in other geographic regions. Both inhibin B and FSH are useful markers of spermatogenesis.