<![CDATA[Background: Intravesical Bacillus Calmette–Guérin (BCG) is the current gold standard adjuvant therapy to reduce both recurrence and progression of non-muscle-invasive bladder cancer (NMIBC). On the other hand, there is a growing concern about its possible effect on male fertility. Objective: This narrative review provides an analysis of the recent evidence regarding the impact of intravesical BCG therapy on semen quality and overall male fertility parameters in reproductive-age NMIBC patients. Methods: A targeted literature review was performed for prospective clinical studies assessing semen parameters and reproductive hormones before and after intravesical therapy. A narrative review was conducted that included studies eligible for inclusion (up to date through October 2023) to describe comparative changes in semen quality and endocrine function by comparing BCG-treated men with matched cohorts following exposure. Results: Intravesical BCG was associated with decreased sperm concentration and motility, in some cases with progression to oligospermia and abnormal sperm morphology including "amorphous" heads, bent necks, and short tails—although results were inconsistent. Although early studies found stable hormonal profiles, recent data have shown increases in follicle-stimulating hormone and testosterone, indicating testicular stress with compensatory feedback mechanisms. Conversely, no adverse reproductive effects were observed with mitomycin C. Conclusions: Intravesical BCG may transiently interfere with spermatogenesis while endocrine function remains intact. These results underline the importance of fertility counseling and semen cryopreservation before intravesical therapy. This needs to be confirmed in larger studies with longer follow-up periods for reproductive outcomes.]]>
