OBJECTIVE: To evaluate the impact of varicocele repair on serum 17-OH progesterone (17-OHP) levels and investigate its relationship with semen parameters and pregnancy outcomes in hypogonadal and eugonadal patients. Additionally, to address the unclear association between varicocele and serum 17-OHP levels in male infertility. METHODS: This prospective study included 135 men who underwent microscopic subinguinal varicocelectomy. Preoperative and postoperative (3-6 months) hormone levels, including follicle-stimulating hormone (FSH), luteinizing hormone (LH), total testosterone (TT), and 17-OHP, and semen parameters, such as total motile sperm count (TMS) and sperm morphology, were analyzed. Patients were categorized as hypogonadal (TT <
300 ng/dL) or eugonadal (TT ≥300 ng/dL). Pregnancy outcomes were recorded over a 12-month follow-up period. RESULTS: Significant increases in TT and 17-OHP levels were observed only in hypogonadal men, while TMS and sperm morphology improved in both groups. In hypogonadal men, changes in serum 17-OHP levels (Δ-17-OHP) positively correlated with TMS improvement (r=0.388, p=0.009). Furthermore, in hypogonadal patients, although not statistically significant, Δ-17-OHP were higher in men whose partners achieved pregnancy compared to those whose partners did not. CONCLUSIONS: Varicocele repair improves semen parameters in both hypogonadal and eugonadal men. In hypogonadal men, increases in Δ-17-OHP are linked to TMS improvements, highlighting its potential as a clinical biomarker. Further studies are warranted to validate 17-OHP as a predictor of pregnancy outcomes.