Distribution and Positive Predictive Value of Follicle Stimulating Hormone Among Nonazoospermic Men

PURPOSE: Our goal was to characterize the distribution of follicle stimulating hormone (FSH) in fertile and subfertile nonazoospermic men, and to determine the ability of various FSH thresholds to predict fertility status. MATERIALS AND METHODS: We performed a retrospective cohort study of 1389 nonazoospermic men who presented for fertility evaluation. Men with at least 2 semen analyses and 1 FSH level were included. Men were dichotomized into fertile and subfertile groups based on total motile sperm count. FSH was evaluated within a multivariable model, and positive predictive values (PPVs) for subfertility were used to assess the clinical utility of various FSH thresholds. RESULTS: One thousand fifteen (80%) men were classified as fertile and 274 (20%) as subfertile. Age, presence of varicocele, and testosterone levels were not statistically different between the groups. Median FSH was 4.0 vs 6.0 (P < .001) among fertile vs subfertile men. Multiple FSH thresholds ranging from 2.9 to 9.3 performed similarly in predicting fertility status (PPV 0.49-0.59). Only FSH thresholds above the 95th percentile (12.1) had PPVs greater than 0.7. The highest PPV (0.84) was seen at an FSH of 20.8 (99th percentile). CONCLUSIONS: While there were significant differences in FSH levels among fertile and subfertile nonazoospermic men, multiple FSH cutoffs between 2.2 and 9.3 performed poorly for prediction of fertility status as determined by total motile sperm count. It was not until the 95th percentile FSH value that a clinically useful level of predictability for subfertility was reached, indicating that FSH should not be used as a standalone test of fertility status. Nonetheless, FSH testing remains clinically useful and may be most informative in the setting of extreme values or discordant FSH and semen analysis results.