Serum total testosterone and testicular histology help predicting positive sperm retrieval in non-mosaic Klinefelter patients undergoing testicular sperm extraction: real-life data from a large multicenter cohort

Objective: To study real-life rates and predictors of sperm retrieval (SR) in men with non-mosaic Klinefelter syndrome (KS) seeking medical help for primary male factor couple's infertility. Design: Multicenter, retrospective, cohort study. Subjects: Data analysis from 383 non-Finnish, white-European, non-mosaic KS men with non-obstructive azoospermia (NOA) undergoing TESE between 2008 and 2024 at 12 tertiary referral centers in Italy. Exposure: All patients received a comprehensive diagnostic work-up, including hormonal/genetic tests and testicular ultrasound. Semen analysis followed 2021 World Health Organization criteria. Testicular histology was recorded. Either conventional testicular sperm extraction (cTESE) or microsurgical TESE (mTESE) was used, depending on surgeon preference. Descriptive statistics and logistic regression assessed predictors of positive SR (+SR). Main outcome measures: Positive sperm retrieval rate (+SRR) in non-mosaic KS men undergoing cTESE or mTESE for NOA, and the identification of clinical and histological predictors associated with +SR. Results: Median (IQR) age was 31 years (25-36) and testicular volume was 3.8 ml (3-5) ml. Baseline follicle-stimulating hormone and total testosterone (tT) levels were 31.2 mUI/mL (21.5-41.8) and 3.6 ng/mL (2.7-5.1), respectively. Of 383, 50 (13.1%) patients have been on continuous testosterone therapy (TTh) prior to surgery, which has been interrupted at least 6 months before c/mTESE. Of all, 246 (64.2%) men underwent cTESE and a bilateral c/mTESE procedure was carried out in 345 (90.1%) men. Histologic reports showed Sertoli cell-only syndrome (SCOS), maturation arrest (MA) and hypospermatogenesis (HS) in 350 (91.4%), 20 (5.2%) and 13 (3.4%) patients, respectively. Overall, +SR was found in 114 (29.8%) men. Patients with +SR had higher tT values (3.8 vs. 3.6 ng/ml, p=0.03) than those with -SR. SCOS histology was more frequently associated with -SR compared to both MA and HS (p<0.001). Multivariable logistic regression analysis confirmed that higher baseline tT values (OR 1.1, 95% CI 1.02-3.45, p=0.03) and HS histology (8.8, 95% CI 2.96-15.76, p<0.001) were independently associated with +SR. Conclusions: One third of non-mosaic KS men had +SR at c/mTESE. Higher preoperative tT and testicular histology emerged to be independently associated with SR outcomes. These findings can be clinically useful for a tailored counselling before c/mTESE in non-mosaic KS men with NOA.