Editorial Comment to the Change of Nocturnal Penile Tumescence During Dutasteride Administration

The widespread use of dutasteride, a dual 5 alpha-reductase inhibitor (5-ARI), for benign prostatic hyperplasia (BPH) necessitates a clear understanding of its common side effect: erectile dysfunction (ED). This prospective study makes a significant advancement by incorporating an objective assessment tool, the electrometer [1], to measure maximal penile circumferential change (MPCC) during nocturnal penile tumescence (NPT), unlike previous reports using self-assessment questionnaires such as SHIM and EHS, moving beyond the reliance on subjective questionnaires. The study's most critical finding is the discrepancy observed after 6 months of treatment [2]. The SHIM score, which reflects subjective sexual function and satisfaction, significantly declined, consistent with previous reports indicating an increased risk of self-reported sexual dysfunction with 5-ARIs. Conversely, MPCC, a measure of organic erectile capacity, showed no significant reduction. Discrepancies between NPT and questionnaire results are not uncommon [3]. This is because the NPT mainly reflects organic erectile function, while the SHIM evaluates subjective sexual function, including erectile function and satisfaction in real life, as well as psychosocial factors. However, the fact that EHS and MPCC are correlated, as reported by the authors, makes this discrepancy interesting [4]. The absence of significant changes from baseline in both EHS and MPCC at 6 months may be related to this. This maintenance of objective function is subject to several biological and methodological considerations. The study lacked measurement of serum androgens. Dutasteride inhibits the conversion of testosterone to dihydrotestosterone (DHT), often leading to a compensatory increase in testosterone levels. This elevated circulating testosterone, which supports the physiological process of NPT, may have protected or compensated for any potential immediate organic decline caused by DHT suppression. This highlights the crucial need for future studies to correlate androgen levels with objective NPT findings. Furthermore, the short observation period of 6 months may be insufficient to capture potential long-term, structural changes in penile tissue. The objective decline might manifest only after more prolonged exposure. The small sample size (n = 20) and the advanced age of the participants are also pertinent limitations, which the authors suggest may explain the lack of correlation between EHS and MPCC observed in this cohort. In conclusion, this research provides a valuable clinical distinction. While the patient's subjective experience and self-perception may deteriorate early in dutasteride treatment, their underlying organic erectile capacity appears to be preserved in the short term. Clinical guidance for patients should incorporate this understanding, utilizing objective assessment tools to accurately differentiate between psychosocial and organic components of 5-ARI-related ED. Large-scale, long-term studies integrating androgen profiling with NPT monitoring are necessary to fully map the temporal course of this critical side effect. The author takes full responsibility for this article. The author declares no conflicts of interest. This article is linked to Matsuki et al. papers. To view this article, visit https://doi.org/10.1111/iju.70291.