This retrospective observational study evaluated the diagnostic and predictive value of serum Inhibin B (INHB), follicle-stimulating hormone (FSH), and the INHB/FSH ratio in differentiating histopathological subtypes of non-obstructive azoospermia (NOA) in men undergoing microdissection testicular sperm extraction (micro-TESE). Seventy-three patients treated at a single tertiary referral center between January 2023 and September 2025 were included. Hormonal parameters were assessed preoperatively, and histopathological findings were categorized into five groups (SCOS, EMA, LMA, HSG, NS). The INHB/FSH ratio demonstrated significant discriminative ability across histopathological patterns and showed strong predictive performance in ROC and regression analyses. These findings suggest that the INHB/FSH ratio may serve as a practical, non-invasive biomarker for estimating testicular pathology severity in NOA patients.

Non-obstructive azoospermia (NOA) represents a severe form of male infertility characterized by impaired spermatogenesis. Although microdissection testicular sperm extraction (micro-TESE) remains the gold standard for sperm retrieval in these patients, predicting underlying histopathology before surgery remains clinically challenging. Identifying reliable non-invasive biomarkers may improve patient counseling and optimize surgical decision-making.

This retrospective observational study was conducted at Elazığ Fethi Sekin City Hospital, Türkiye. Medical records of men diagnosed with NOA who underwent micro-TESE between January 2023 and September 2025 were reviewed. Patients with obstructive azoospermia, known endocrine disorders, or incomplete clinical data were excluded.

Preoperative serum levels of FSH, luteinizing hormone (LH), total testosterone, and Inhibin B were measured within three months prior to surgery using standardized immunoassay methods. The INHB/FSH ratio was calculated for each patient.

Histopathological evaluation of testicular tissue samples obtained during micro-TESE was performed by an experienced pathologist blinded to hormonal results. Patients were categorized into five histopathological groups: Sertoli Cell-Only Syndrome (SCOS), Early Maturation Arrest (EMA), Late Maturation Arrest (LMA), Hypospermatogenesis (HSG), and Normal Spermatogenesis (NS).

The primary outcome measure was the association between the INHB/FSH ratio and histopathological classification. Statistical analyses included descriptive statistics, non-parametric group comparisons, receiver operating characteristic (ROC) curve analysis to determine discriminative performance, and multivariable regression models to evaluate predictive relationships.

This study aimed to clarify whether the INHB/FSH ratio could serve as a clinically useful marker for estimating testicular pathology severity in men with NOA undergoing micro-TESE.

Inclusion Criteria:

• Male patients who underwent micro-TESE for non-obstructive azoospermia
• Available histopathological evaluation of testicular tissue
• Available preoperative serum hormone measurements (FSH, LH, testosterone, Inhibin B)

Exclusion Criteria:• Obstructive azoospermia

• Incomplete clinical, hormonal, or histopathological data
• Previous testicular malignancy
• History of chemotherapy or radiotherapy affecting spermatogenesis

Adult male patients diagnosed with non-obstructive azoospermia who underwent micro-TESE at a tertiary referral center and had available histopathological and hormonal evaluation data.