Re-assessment of the close relationship between serum FSH levels and semen quality: a retrospective cohort study of 11,929 Chinese men.

PURPOSE

To establish a medically valuable normal reference interval of follicle-stimulating hormone (FSH) levels in males with normal semen and to assess the predictive value of FSH in males exhibiting semen abnormalities.

METHODS

The study involved male patients who underwent their initial serum sex hormone test and semen test between October 2013 and June 2023. The reference interval was identified as the 95% confidence interval (CI) of FSH values in the patients with normal semen parameters. Then, in the total study population, receiver operating characteristic (ROC) curves were performed to evaluate the discriminatory ability of FSH for oligozoospermia and non-obstructive azoospermia (NOA). Besides, multivariable logistic regression was performed to investigate the association of FSH with oligozoospermia and NOA adjusted by age.

RESULTS

A total of 11,929 patients were finally enrolled in the study. The normal reference interval of FSH ranged from 1.70 IU/L to 7.60 IU/L (median: 3.98 IU/L) based on 4595 patients with normal semen routine parameters. In the total patients, ROC curves showed FSH to have a "fair" discriminatory ability for oligozoospermia (area under receiver operating characteristic curve (AUC) 0.747, threshold 7.32 IU/L, accuracy 0.734, positive predictive value (PPV) 0.754, negative predictive value (NPV) 0.726), while ROC curves showed FSH to have a "excellent" discriminatory ability for NOA (AUC: 0.921, threshold 10.18 IU/L, accuracy 0.903, PPV 0.593, NPV 0.972). Besides, multivariable logistic regression showed that FSH ≥ 7.32 IU/L was associated with a 8.51-fold increase in the risk of oligozoospermia adjusted by age, while FSH ≥ 10.18 IU/L was associated with a 38.93-fold increase in the risk of NOA.

CONCLUSIONS

Our findings indicated that the reference interval for FSH in males with normal semen was 1.70-7.60 IU/L and found that FSH was capable of effectively discerning oligospermia and NOA.