Associations between circulating sex hormones and anterior urethral stricture disease

Introduction

Anterior urethral stricture disease (aUSD) is a common urologic pathology that causes obstructive lower urinary tract symptoms (1). Most aUSD cases are classified as idiopathic (2). A better understanding of the molecular pathophysiology is needed to understand stricture development, progression, and recurrence after treatment to improve aUSD prevention and efficacy of non-urethroplasty surgical treatments.

Our group recently found an association between the presence of aUSD and higher serum levels of pro-fibrotic and pro-inflammatory cytokines (3). In addition, a higher-than-expected incidence of chronic inflammation within idiopathic strictures was noted. The causal association remains unclear, though emerging evidence suggests that circulating androgens may play a role, as testosterone is known to be instrumental for both in-utero male urethra development, the promotion of periurethral vasculogenesis, and in urethral wound healing (4-6). Low testosterone has been associated not only with states of increased inflammation and fibrosis, but also with male urethra-specific pathology. In addition, low testosterone is associated with the presence, length, and recurrence of urethral strictures and erosion of artificial urinary sphincter cuffs (7-12).

The purpose of the current study was to contribute to the growing body of literature addressing the relationship between circulating sex hormones (cSHs) and aUSD. Our overall hypothesis was that cSH levels would associate with the presence of aUSD, aUSD characteristics, and stricture inflammation. We present this article in accordance with the STROBE reporting checklist (available at https://tau.amegroups.com/article/view/10.21037/tau-2026-0268/rc).

Methods

Patient cohort

Stricture and control cohort information has previously been described by Gutierrez et al. in the primary study analyzing this data set (3). Briefly, patients were enrolled at 5 academic centers in a National Institute of Diabetes and Digestive and Kidney sponsored study (1R21DK115945-01) evaluating the role of inflammation in aUSD. Patients were included in the stricture cohort if they were males >18 years old with aUSD who were undergoing anterior urethroplasty. Their strictures were classified using the previously described Length, Segment, Etiology (LSE) system (13). Patients were excluded if the aUSD represented a recurrence at the site of a prior urethroplasty, the aUSD was associated with radiotherapy or hypospadias repair, or the surgeon suspected malignancy at time of urethroplasty. In addition, patients that were actively utilizing intermittent catheterization, we actively taking testosterone supplementation, or had a transurethral dilation/incisional procedure within 3 months of the urethroplasty date we excluded. A total of 154 males were included in the stricture cohort. A control group (n=9) of men without active urologic conditions not receiving testosterone supplementation undergoing vasectomy was recruited to provide blood and serum.

Study materials

Serum stored from the original aUSD inflammatory study was used for this secondary data analysis (3). The serum was obtained on the morning of surgery at the time of peripheral intravenous catheter placement (stricture cohort) or at the time of vasectomy (control cohort). All study patients had baseline demographic and stricture characteristics collected at the time of enrollment.

Serum sex hormones were analyzed using enzyme-linked immunosorbent assay (ELISA) kits from Eagle Biosciences (Amherst, New Hampshire, USA), including total testosterone (TT) (range, 0.08–16.7 ng/mL; TST31-K01), free testosterone (fT) (range, 0.1–60 pg/mL; TSF31-K01), total estrogen (range, 20–2,500 pg/mL; ESG31-K01), progesterone (Pr) (range, 0.3–60 ng/mL; PRG31-K01), and cortisol (Co) (range, 0.5–60 µg/dL; COR31-K01). Samples were processed per manufacturer instructions in duplicate.

Statistical analysis

The primary study cohorts were (I) patients with aUSD and (II) controls. Within the stricture cohort, subcohorts were created based on stricture etiology (idiopathic, lichen sclerosus, and trauma & iatrogenic), and by the presence of inflammation within the urethral stricture tissue obtained at the time of urethroplasty (3). Briefly, stricture specimens were stained with hematoxylin and eosin and graded by two pathologists for inflammation severity (none, minimal, mild, moderate, severe) based upon the volume of inflammatory cells and depth of epithelial penetration (14). The study questions were as follows: (I) do demographic features and cSH levels differ between control and stricture cohorts? Student’s t-tests were used for the analysis (Table 1); (II) is there a difference in the odds of stricture based on the levels of cSH levels? Univariate logistic regression was used for the analysis (Table 2); (III) do significant differences in the odds of stricture given cSH levels remain after adjusting for age, body mass index (BMI), and co-morbid diabetes? Multivariable logistic regression was used for the analysis (Table 3); (IV) do demographic features and cSH levels differ between strictures of different etiologies in the stricture cohort? One-way analysis of variance (ANOVA) was used for the analysis (idiopathic, lichen sclerosus, and trauma & iatrogenic) (Table 4); (V) do demographic features and cSH levels differ within the stricture cohort based on inflammation being present in the urethroplasty tissue specimen? Student’s t-tests were used for the analysis followed by multivariable logistic regression to control for potential confounding factors (Tables 5-7); (VI) do demographic features and cSH levels differ between strictures of different length in the stricture cohort? One-way ANOVA was used for the analysis (L1: ≤2 cm, L2: >2 cm, ≤7 cm, L3: >7 cm) (Table 8) (13,15). Tukey’s multiple comparisons of means was used for the post-hoc analysis of significant differences. Missing data, either because of insufficient serum collection or a faulty ELISA test, were excluded with listwise deletion. Pearson’s correlations coefficients were used for analysis (Table 9). All data were analyzed using R Statistical Software (v4.2.2) and GraphPad Prism 9.

Results

Age was the only demographic feature that significantly differed between stricture and control cohorts with the median age of stricture cohort males being 47.5 and 32 years in the controls (Table 1). Of the five types of cSHs analyzed, fT levels appreciably differed between the stricture and control cohorts (1.08 vs. 2.13 pg/dL, P=0.046) as shown in Figure 1 and Table 1.

Figure 1 Free testosterone is lower in the stricture cohort compared to the healthy control group. T-test was used to compare means.

There was a statistically significant decrease in odds of stricture as fT levels increase [odds ratio (OR): 0.29, 95% confidence interval (CI): 0.13–0.60, P<0.01]; a 1-unit increase in fT results in a 71% decrease in the odds of having stricture as determined by a univariate model Table 2. After adjusting for confounding factors (age, BMI, diabetes), the statistically significant relationship remained, with a 1-unit increase in fT associated with a 67% decrease in the adjusted odds of having stricture [adjusted OR (aOR): 0.33, 95% CI: 0.13–0.81, P=0.02] as shown in Table 3.

Charlson Comorbidity Index, BMI, and diabetes significantly differed within the cohort between stricture etiologies, with lichen sclerosus strictures associated with a higher median BMI than idiopathic or trauma & iatrogenic strictures (Table 4) (16,17). No differences were found in levels of cSHs between stricture etiologies (Table 4). Table 5 shows differences in demographics and cSH levels within the stricture cohort between the presence or absence of local inflammation. Cohort subjects with local stricture inflammation were significantly younger than those without inflammation (42 vs. 52 years, P=0.048). Strictures with inflammation were also associated with higher levels of TT (619 vs. 411 ng/dL, P=0.03) and Pr (0.450 vs. 0.350 ng/dL, P=0.049), but these associations were lost after adjusting for confounding variables (Tables 6,7).

Table 8 shows increasing stricture length associated with increasing age, comorbidities, and BMI. Increasing stricture length was also significantly associated with decreasing fT (Table 8). Longer strictures (L2, L3) had lower fT levels compared to L1 (≤2 cm) strictures (Table 9, Figure 2).

Figure 2 Free testosterone decreases with increasing stricture length. One-way ANOVA was used to compare means. L1: ≤2 cm, L2: >2, ≤7 cm, L3: >7 cm. ANOVA, analysis of variance.

Discussion

CSHs and aUSD

The main objective of our study was to assess the relationship between cSHs and aUSD. We hypothesized that cSH levels would be associated with the presence of aUSD and stricture etiology, length, and local inflammation. Our results revealed significant associations between lower fT and both adjusted odds of stricture and increased length of strictures. However, no other significant cSH associations were noted.

There have been three prior studies of significance that have examined the relationship between testosterone and aUSD. Mondal et al. compared 40 males with atraumatic aUSD with 40 age-matched controls and noted lower TT levels in the stricture group (9). Within the stricture cohort, low TT levels were also associated with longer strictures and urethroplasty recurrence. Spencer et al. retrospectively reviewed 115 men with aUSD and noted that 57% had clinically low TT levels versus 28% of age-matched controls (8). Hypogonadism was again associated with longer aUSD. The only study that specifically evaluated fT and strictures was conducted by Puche-Sanz et al., who found significantly lower TT in 149 males with urethral strictures compared to 67 males without strictures. Additionally, every 100-unit increase in TT associated with a 34% decrease in the adjusted odds of having urethral stricture (7). While they did not find a significant difference in fT or bioavailable testosterone, they did find that for every 1-unit increase in fT and 10-unit increase in bioavailable testosterone, there was an 18% and 10% decrease in the adjusted odds of having stricture, respectively.

Additional evidence for the relationship between urethral health and testosterone comes from the artificial urinary sphincter (AUS) literature. Hofer et al. evaluated 53 men undergoing AUS procedure, in which 20 men suffered cuff erosion (11). Of the men with eroded sphincters, mean time to erosion was 1.70 years and 90% of these cases had low testosterone. A follow-up study by Wolfe et al., confirmed this association in a retrospective study of 161 men with AUS, finding that 30 (71.4%) of the 42 men with cuff erosion had low testosterone (10). They concluded that men with low testosterone were nearly three times more likely to suffer AUS erosion.

The pathophysiology of this association between low testosterone and urethral pathology is unknown. However, histopathologic specimens from urethral strictures have demonstrated a paucity of androgen receptors, angiopoietin 1 receptors, and vessel density in men with low testosterone compared to men with normal testosterone levels and urethral strictures (4). Thus, what may link the associations between low testosterone and both AUS erosion and aUSD is an impaired ability to heal the urethra after an insult. In the AUS population, that insult may simply be the repetitive opening and closing of the cuff. The causative insult for urethral stricture disease may be more varied, including endourologic procedure (E3a—iatrogenic), external trauma (E1), or lichen sclerosus (E6), per the LSE aUSD Classification System (15). While a normally perfused and robust urethra may be expected to heal itself after an otherwise sub-clinical insult, a urethra in the setting of low testosterone, especially the active form of testosterone (fT), may heal with fibrosis, leading to stricture. This two-hit hypothesis—insult plus innate inability to regenerate damaged urethra—may explain some of the emerging evidence of aUSD being an inherited process (18).

As postulated by others, the clinical implications of our findings may mean that supplemental testosterone should be considered before urethroplasty in men with low testosterone. However, whether routine testosterone levels should be checked before urethroplasty is unknown. Furthermore, we do not yet understand if supplemental testosterone pre-urethroplasty will directly improve urethral health, or if supplemental testosterone might be used as an adjunct to urethroplasty to improve surgical success. Given the multitude of studies now supporting this association, further prospective work is warranted.

Limitations

Our study has limitations that deserve mentioning. First, this was a cross-sectional study which prevents the establishment of causal relationships between findings in cSH levels and stricture presence and features. Second, our small sample size may have prevented resolution of significant associations. For example, TT, fT, and estradiol (Es) levels are appreciably lower in lichen sclerosus compared to idiopathic strictures, however no significant difference was detected. Additionally, our small control cohort may have prevented our association between fT levels and No Stricture vs. Stricture from reaching statistical significance. Third, there was a significant difference in age between control and stricture groups, the former being significantly older (47.5 vs. 32 years old). While there is a well-established association between increasing age and decreasing testosterone, the significant association we found between the odds of stricture given lower fT held when we controlled for age as a confounding factor in our univariate and multivariable analysis (19). Fourth, while study serum was drawn in the morning prior to urethroplasty or at the time of surgery, the timing varied amongst institutions and was not standardized. Thus, while all blood draws were performed in the early morning, the exact timing of the blood draw was variable and not recorded, and thus, the known diurnal variation may be affecting the hormonal levels. Finally, the range of the ELISA we used to measure fT is lower than the range usually measured in the clinical setting (0.1–60 vs. 35–155 pg/mL). Thus, the specific hormonal values reported in our study are significantly lower than found with standardized, non-ELISA testing and the specific values can therefore, not be directly compared to prior studies.

Conclusions

In our study measuring cSHs of 154 patients undergoing anterior urethroplasty for aUSD, we observed a statistically significant decrease in the odds of stricture with increasing fT levels. Additionally, aUSD patients with lower fT presented with longer strictures. These findings contribute to the growing body of literature documenting the relationship between testosterone and aUSD, though the specific pathophysiology remains unknown. Further studies will be needed to determine the role that testosterone replacement and supplementation has on aUSD prevention, treatment and urethroplasty success.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://tau.amegroups.com/article/view/10.21037/tau-2026-0268/rc

Peer Review File: Available at https://tau.amegroups.com/article/view/10.21037/tau-2026-0268/prf

Funding: This work was supported by the National Institute of Diabetes and Digestive and Kidney Diseases (1R21DK115945-01), the University of Iowa Medical Scientist Training Program (T32 GM139776), and a University of Iowa Andrew Schulte Educational Grant.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tau.amegroups.com/article/view/10.21037/tau-2026-0268/coif). J.B.M. serves as an unpaid editorial board member of Translational Andrology and Urology from August 2024 to July 2026. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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