The Importance of Discordant Follicle Stimulating Hormone and Inhibin B Levels in Primary Infertile Men: Findings from a Cross-Sectional Study.

Purpose: We aimed to investigate the relationship between follicle stimulating hormone (FSH) and inhibin B (InhB).

Materials and methods: Data from 1,230 consecutive men presenting for primary couple's infertility were analyzed. Health-significant comorbidities were scored with Charlson comorbidity index. Quartiles of FSH and InhB were considered to determine threshold values. Descriptive statistics and logistic regression models tested association between FSH and InhB values.

Results: Overall, 1,080 (87.8%) men had concordant FSH and InhB values. Conversely, 150 patients (12.2%) had discrepancies in FSH and InhB, with 78 (6.3%) and 72 (5.9%) men reporting both low and high FSH and InhB values, respectively. Infertile men with discordant values were younger (median [interquartile range] 38.0 years [34-41 years] vs. 36.0 years [31-40 years]); had smaller testicular volume (TV) (12 mL [10-15 mL] vs. 15 mL [12-20 mL]); and, had more frequently a sperm DNA fragmentation test >30% (179 [59.1%] vs. 40 [78.4%]) than those with concordant values (all p<0.05). Moreover, a higher frequency of previous cryptorchidism (27.3% vs. 11.9%), lower sperm concentration (3.0 million/mL [0.9-11.0 million/mL] vs. 13.8 million/mL [3.1-36.0 million/mL]), lower progressive sperm motility rates (12.0% [5.0%-25.3%] vs. 20.0% [7.0%-36.0%]), and greater rates of non-obstructive azoospermia (36.4% vs. 23.9%) were found in men with discordant FSH and InhB values (all p≤0.005). At multivariable logistic regression analysis, higher body mass index (odds ratio [OR], 1.08; p=0.001), smaller TV (OR, 0.91; p<0.001), and a history of cryptorchidism (OR, 2.49; p<0.001) were associated with discordant FSH and InhB values.

Conclusions: More than one out of ten infertile men had discordant FSH and InhB values in the real-life setting showing worse clinical profiles than those with concordant levels. Smaller TV and history of cryptorchidism could be used as clinical markers to better tailor the need to test InhB.