Penile prostheses harbor biofilms driven by individual variability and manufacturer even in the absence of clinical infection.

BACKGROUND: Culture-based studies have shown that penile prostheses harbor biofilms in the presence and absence of infection, but these findings have not been adequately validated using contemporary microbiome analytic techniques. AIM: The study sought to characterize microbial biofilms of indwelling penile prosthesis devices according to patient factors, device components, manufacturer, and infection status. METHODS: Upon penile prostheses surgical explantation, device biofilms were extracted, sonicated, and characterized using shotgun metagenomics and culture-based approaches. Device components were also analyzed using scanning electron microscopy. OUTCOMES: Outcomes included the presence or absence of biofilms, alpha and beta diversity, specific microbes identified and the presence of biofilm, and antibiotic resistance genes on each prosthesis component. RESULTS: The average age of participants from whom devices were explanted was 61 ± 11 years, and 9 (45%) of 20 had a diagnosis of diabetes mellitus. Seventeen devices were noninfected, and 3 were associated with clinical infection. Mean device indwelling time prior to explant was 5.1 ± 5.1 years. All analyzed components from 20 devices had detectable microbial biofilms, both in the presence and absence of infection. Scanning electron microscopy corroborated the presence of biofilms across device components. Significant differences between viruses, prokaryotes, and metabolic pathways were identified between individual patients, device manufacturers, and infection status. Mobiluncus curtisii was enriched in manufacturer A device biofilms relative to manufacturer B device biofilms. Bordetella bronchialis, Methylomicrobium alcaliphilum, Pseudoxanthomonas suwonensis, and Porphyrobacter sp. were enriched in manufacturer B devices relative to manufacturer A devices. The most abundant bacterial phyla were the Proteobacteria, Actinobacteria, and Firmicutes. Glycogenesis, the process of glycogen synthesis, was among the predominant metabolic pathways detected across device components. Beta diversity of bacteria, viruses, protozoa, and pathways did not differ among device components. CLINICAL IMPLICATIONS: All components of all penile prostheses removed from infected and noninfected patients have biofilms. The significance of biofilms on noninfected devices remains unknown and merits further investigation. STRENGTHS AND LIMITATIONS: Strengths include the multipronged approach to characterize biofilms and being the first study to include all components of penile prostheses in tandem. Limitations include the relatively few number of infected devices in the series, a relatively small subset of devices included in shotgun metagenomics analysis, and the lack of anaerobic and other expanded conditions for culture. CONCLUSION: Penile prosthesis biofilms are apparent in the presence and absence of infection, and the composition of biofilms was driven primarily by device manufacturer, individual variability, and infection, while being less impacted by device component.

Follicle-stimulating hormone modestly predicts improvement in semen parameters in men with infertility treated with clomiphene citrate.

Clomiphene citrate is a commonly prescribed empiric medical therapy for male infertility, but outcomes data and response rates remain incompletely understood. We retrospectively reviewed our single-institutional experience of infertile men prescribed clomiphene. Clomiphene treatment in the final cohort of 140 men was associated with a modest increase in median sperm concentration from 2.2 to 2.5 million/ml (p < 0.001). A total of 46/140 (33%) of men upgraded according to World Health Organization concentration categories. Clomiphene treatment in 26/113 (23%) of previously ineligible men became eligible for intrauterine insemination. Using both univariate and multivariable regression, pre-treatment follicle-stimulating hormone was inversely associated with change in semen concentration with clomiphene treatment. On binary logistic regression, follicle-stimulating hormone level was inversely related to World Health Organization concentration category upgrade (p = 0.01). Unfortunately, 17/140 (12%) of men paradoxically worsened on clomiphene, but no predictors for this could be identified. In summary, clomiphene citrate confers a clinically relevant but modest benefit in a subset (1/3rd ) of infertile men, particularly those with lower pre-treatment follicle-stimulating hormone levels. Men with elevated follicle-stimulating hormone over 15 IU/ml are less likely to benefit from treatment and should be counselled on other relevant treatment alternatives.

Prolactin-to-Testosterone Ratio Predicts Pituitary Abnormalities in Mildly Hyperprolactinemic Men with Symptoms of Hypogonadism.

PURPOSE: We aimed to identify predictor variables associated with pituitary abnormalities in hypogonadal men with mild hyperprolactinemia. We also sought to develop a decision-making aid to select patients for evaluation with pituitary magnetic resonance imaging. MATERIALS AND METHODS: We retrospectively examined men with mild hyperprolactinemia (15.1-50.0 ng/ml) who presented with symptoms of hypogonadism and underwent pituitary magnetic resonance imaging. Demographics, laboratory values and clinical data were obtained from the electronic medical record. Selected predictor variables were included in multivariable logistic regression and partitioning models. Cost avoidance analysis was performed on models achieving sensitivities ≥90%. RESULTS: A total of 141 men were included in the study, of whom 40 (28%) displayed abnormalities on pituitary magnetic resonance imaging. Patients with pituitary abnormalities exhibited higher prolactin (p=0.01), lower testosterone (p=0.0001) and lower luteinizing hormone (p=0.03) levels than those with normal anatomy, as well as higher prolactin-to-testosterone ratios (p <0.0001) and lower luteinizing hormone-to-follicle-stimulating hormone ratios (p=0.0001). These serological variables were identified as the best performing predictor variables. The partition incorporating a prolactin-to-testosterone ratio cutoff of 0.10 and prolactin cutoff of 25 ng/ml achieved 90% sensitivity and 48% specificity, and reduced diagnostic expenses by 28%. CONCLUSIONS: Hypogonadal men presenting with mild hyperprolactinemia and pituitary abnormalities declare themselves via endocrine studies routinely ordered to evaluate these conditions. The prolactin-to-testosterone ratio is the best independent predictor of finding a pituitary abnormality on magnetic resonance imaging, although sensitivity improves by referencing additional serological parameters. Significant cost avoidance may result from screening this population prior to ordering pituitary magnetic resonance imaging.

Pathophysiology and treatment options of varicocele: An overview.

Varicocele is the most common correctable cause for male infertility, but not all men with varicocele are affected equally by this condition. The pathophysiology of varicocele-induced fertility remains ill-defined. While evidence suggests that oxidative stress remains a central factor, other mechanisms likely include scrotal hyperthermia, reflux of metabolites, hypoxia and cadmium accumulation. Microsurgical varicocelectomy remains the gold standard treatment option for infertile men with a clinically palpable varicocele and abnormal semen parameters. Newer evidence suggests a potential role for antioxidant supplementation and a meaningful role of varicocelectomy for patients destined for ART to improve pregnancy outcomes.

Assessing online price transparency of sperm cryopreservation across the United States.

Although the lack of information on the costs and pricing of healthcare services prevails throughout the medical industry, empiric observations have demonstrated that pricing information is even more obscured in the sperm cryopreservation market. Thus, the objectives of our study are to assess and compare online price transparency and the price of sperm cryopreservation across various healthcare settings in the United States. This study examined online pricing published by facilities that have an active registration to store spermatozoa with the Food and Drug Administration. Less than one-fifth of registered facilities display any pricing information online. Price transparency also varies among census regions and facility types. Nationally, the median initial bank fee and annual price of storage are $350 and $385 respectively. Although there were no differences in the initial fee by facility type and census region, the annual price of storing spermatozoa is highest in the Northeast, which could be attributed to laboratory techniques, demographic patterns or insurance coverage. Guidelines from professional societies or different legislation and regulatory requirements across different US states can increase price transparency, which can promote consumer decision-making and decrease the barrier for men seeking fertility preservation.

The microbiome of the infertile male.

PURPOSE OF REVIEW: Contrary to historic dogma, many tissues and organs in the human body contain a resident population of bacteria, fungi, and viruses collectively known as the microbiome. The microbiome plays a role in both homeostatic symbiosis and also pathogenic dysbiosis in a wide array of diseases. Our understanding of the relationship between the microbiome and male factor infertility is in its infancy but is slowly evolving. RECENT FINDINGS: Recent literature indicates that semen (and likely the testis) is not sterile and contains a distinct microbiome, and these changes in its composition are associated with alterations in semen quality and fertility status. Preliminary investigation indicates that manipulating the human microbiome may have implications in improving semen parameters and fertility. SUMMARY: In this review, we describe relationships between the microbiome and the genitourinary system, discuss the prior work on the relationship among bacteriospermia, leukocytospermia and male factor infertility, and summarize the current literature utilizing 16s rRNA-based next-generation sequencing on the seminal and testicular microbiome. We explore the specific microbial taxa implicated in various aspects of spermatic dysfunction and introduce preliminary evidence for therapeutic approaches to alter the microbiome and improve fertility status.

The effect of trainee involvement on surgical outcomes and complications of male infertility surgical procedures.

In this study, we sought to determine the effect of trainee (resident or fellow physician) involvement in male infertility surgical procedures on patient surgical outcomes and complications. The American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database was retrospectively reviewed for fertility surgical procedures from 2006 to 2012. The procedures included were as follows: epididymectomy, spermatocelectomy, varicocelectomy ± hernia repair, ejaculatory duct resection, vasovasostomy, vasoepididymostomy and 'unlisted procedure male genital system' (to capture sperm retrieval procedures). A variety of peri- and post-operative outcomes were examined. Trainee and nontrainee-involved groups were compared by Wilcoxon rank sum tests, followed by logistic regression, univariate and multivariate analyses. 924 cases were included: 309 with trainees and 615 without. The median post-graduate trainee year was 3 (range: 0-10). Patients in the trainee-involved cohort had higher rates of chronic obstructive pulmonary disease, steroid usage and black race. Mean operative time was 42.5% longer in trainee-involved cases, even after controlling for other covariates (76.2 vs. 49.5 min, p = .00). Hospital stay length was also longer in trainee-involved cases (0.41 vs. 0.35 days, p = .02). There were no differences in superficial infections (p = 1.00), deep wound infections (p = 1.00), urinary tract infections (p = .26), or reoperations (p = .23) with or without trainee involvement.

The Evolving Landscape of Male Varicocele Pathophysiology in the Era of Multi-Omics: A Narrative Review of the Current Literature.

Male-factor infertility is implicated in over half of the millions of cases of infertility worldwide, and varicoceles are the most common correctable cause of male-factor infertility. The pathophysiologic mechanism for varicoceles is complex and next-generation technologies offer promising insights into the molecular underpinnings of this condition. In this narrative review, we highlight historical and contemporary paradigms associated with varicoceles, with an emphasis on the biological underpinnings of this disease. Specifically, we review the literature describing the underlying causes of varicoceles, discuss the molecular and cellular mechanisms causing pathological changes in some (but not all) men, and highlight key articles regarding the next-generation analyses (e.g., transcriptome, epigenome, proteome, and microbiome) being applied to better understand the condition and its treatment. These data demonstrate an ongoing evolution of the knowledge of varicoceles and the potential for improved personalized care in the future for men with this condition.

The effect of red blood cell disorders on male fertility and reproductive health.

Male infertility is defined as a failure to conceive after 12 months of unprotected intercourse owing to suspected male reproductive factors. Non-malignant red blood cell disorders are systemic conditions that have been associated with male infertility with varying severity and strength of evidence. Hereditary haemoglobinopathies and bone marrow failure syndromes have been associated with hypothalamic-pituitary-gonadal axis dysfunction, hypogonadism, and abnormal sperm parameters. Bone marrow transplantation is a potential cure for these conditions, but exposes patients to potentially gonadotoxic chemotherapy and/or radiation that could further impair fertility. Iron imbalance might also reduce male fertility. Thus, disorders of hereditary iron overload can cause iron deposition in tissues that might result in hypogonadism and impaired spermatogenesis, whereas severe iron deficiency can propagate anaemias that decrease gonadotropin release and sperm counts. Reproductive urologists should be included in the comprehensive care of patients with red blood cell disorders, especially when gonadotoxic treatments are being considered, to ensure fertility concerns are appropriately evaluated and managed.

Sperm chromatin dispersion assay reliability and assisted reproductive technology outcomes: Systematic review and meta-analysis.

OBJECTIVE: Elevated sperm DNA fragmentation has potential implications for semen quality and fertility. The commonly used sperm chromatin dispersion test offers an indirect estimation but has limitations in terms of bias and variability. This study aimed to assess the reliability of the sperm chromatin dispersion assay for predicting assisted reproductive technology outcomes. MATERIALS AND METHODS: This systematic review included studies published until December 2023 that adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. PubMed/MEDLINE, Scopus, and Google Scholar databases were searched. Various assisted reproductive technology outcomes in patients with high (≥ 30%) versus low (< 30%) sperm DNA fragmentation were compared using a sperm chromatin dispersion assay and including a sub-analysis of intracytoplasmic sperm injection versus in vitro fertilization. A comprehensive meta-analysis software facilitated quantitative analysis with statistical comparisons between cases and controls. Interstudy heterogeneity was assessed, and sensitivity and publication bias tests were performed. RESULTS: Of the 199 abstracts assessed, 64 full-text articles were screened, and 44 articles were qualitatively synthesized. Fourteen articles representing 5346 participants were quantitatively analyzed. Using the sperm chromatin dispersion assay, elevated sperm DNA fragmentation was associated with lower fertilization and embryo cleavage rates. Notably, high sperm DNA fragmentation levels did not affect the clinical pregnancy, implantation, miscarriage, or live birth outcomes. Sub-analysis revealed lower fertilization, embryo cleavage, clinical pregnancy, live birth rates, and higher miscarriage rates in the intracytoplasmic sperm injection subgroup only. CONCLUSIONS: The sperm chromatin dispersion assay did not show significant differences in pregnancy or live birth rates between the high- and low-sperm DNA fragmentation groups. Noteworthy, high sperm DNA fragmentation was associated with worse assisted reproductive technology outcomes in the intracytoplasmic sperm injection group. Given the current quality of the evidence, affected by the experimental design and the absence of correction for female factors of infertility, clinicians should be wary of the assay's limited predictive power for pregnancy and live birth outcomes.

Combination clomiphene citrate and anastrozole duotherapy improves semen parameters in a multi-institutional, retrospective cohort of infertile men.

In men with impaired semen parameters, empiric medical therapies such as clomiphene citrate, a selective estrogen receptor modulator (SERM), and anastrozole, a selective aromatase inhibitor, are often employed. The effects of jointly administering these agents on semen parameters are not well understood. Here, we describe the findings of our multi-center, retrospective cohort study of men with idiopathic primary or secondary infertility. Twenty-one men were treated with combination therapy (anastrozole and clomiphene) and 69 men were treated with monotherapy (anastrozole). Patients with pre-treatment normozoospermia and recent or current exogenous testosterone therapy were excluded. Baseline and post-treatment semen and sex hormone parameters were compared among groups. The median follow-up duration was 91 days [interquartile range (IQR), 64-117 days]. Following treatment, 43% of men in the combination therapy group demonstrated normozoospermia, compared to 25% in the monotherapy group. Furthermore, men in the combined group demonstrated marked improvements in total motile sperm count (TMSC) [11.3 vs. 2.1 million (M), P=0.03]. There were no significant differences in hormone levels among the two groups following treatment. Combination therapy with clomiphene citrate and anastrozole was associated with modest benefits in post-treatment semen parameters, when compared to anastrozole monotherapy. These benefits may contribute to improvements in pregnancy outcomes with less invasive assisted reproductive technologies, such as intrauterine insemination (IUI). Future investigations with larger sample sizes and prospective study designs are necessary.

Sperm Concentration Remains Stable Among Fertile American Men: A Systematic Review and Meta-Analysis.

IMPORTANCE: Findings from several high-profile meta-analyses have raised concerns about an ongoing global decline in sperm concentration and male fertility. However, these studies exhibit considerable heterogeneity in key variables including study population, methodology, fertility status, and geographic region. OBJECTIVE: To perform a systematic review and meta-analysis exploring temporal trends in sperm concentration among fertile men and men unselected for fertility status in the United States. DATA SOURCES: A literature search performed in Scopus and PubMed databases for studies published between 1970-2023. Additional studies were included from citations of prior global meta-analyses and reviews evaluating temporal trends in sperm count. Study selection and synthesis: Studies were included if they presented original data on sperm concentration in U.S. men without known infertility from 1970 to 2023. Aggregate data were assessed across all study populations, with additional subgroup analyses stratified by fertility status and U.S. region. MAIN OUTCOMES: Weighted generalized linear models were generated to evaluate the association between mean sperm concentration and sample collection year. RESULTS: A total of 874 articles were screened, with 58 meeting the inclusion criteria. These represented 75 unique study populations totaling 11,787 men in the U.S. Across all study populations, no change in sperm concentration was observed between 1970-2018 in unadjusted models (ß=0.14million/mL/year, p=0.42). When adjusting for U.S. region, no statistically significant decline in sperm concentration was seen. When adjusting for both region and fertility status, a modest annual decline was observed to meet statistical significance (ß=-0.35million/ml/year, p=0.04). Of the 49 study populations reporting adequate data to determine mean total sperm count, there was a significant increase in total sperm count of 2.9 million/year between 1970 and 2018 (p=0.03). Subgroup analysis found no statistically significant change in mean sperm concentration among any U.S. census region or fertility status cohort. CONCLUSION AND RELEVANCE: In contrast to prior global studies, this analysis suggests no clinically significant decline in sperm concentration among confirmed fertile men and the general male U.S. population without known infertility. While these findings provide some reassurance against a widespread rapid decline, further studies are necessary to better understand this important topic.

Rising vasectomy volume following reversal of federal protections for abortion rights in the United States.

In June 2022 the United States Supreme Court issued a ruling in the case Dobbs v. Jackson that overturned Roe v. Wade, the 1973 ruling establishing a federally protected right to abortion in the United States. Anecdotal reports suggested increased vasectomy volume following this event; however, no published data exist. We sought to describe trends in vasectomy consultation before and after the Dobbs v. Jackson ruling (referred to as pre- and post-Dobbs herein). Following IRB approval, we reviewed charts of all adults seeking vasectomy consultation in July-August 2021 and July-August 2022 at a large healthcare organization. We then aggregated vasectomy procedural billing data from 2018 to present. The primary outcome was volume of vasectomy consultation appointments and the secondary outcome was number of vasectomies performed. In July-August 2021 (Pre-Dobbs), 116 men attended vasectomy consultation versus 142 men in July-August 2022 (Post-Dobbs). Median age Post-Dobbs was significantly younger than Pre-Dobbs (35 vs 38 years, respectively, p = 0.01) with a significant increase in Post-Dobbs men under 30 seeking vasectomy (p = 0.005). A total of 16.9% (24/142) of Post-Dobbs men were childless, compared to 8.6% (10/116) of Pre-Dobbs men (p = 0.05). Of those with children, median number of offspring was unchanged at 2. Billing data showed a significant increase in vasectomy procedural volumes Post-Dobbs. While overturning Roe v Wade directly impacted female reproductive rights, number of vasectomy consultations and procedures increased significantly following this decision. Younger men, especially those under 30, as well as childless men were significantly more likely to seek consultation Post-Dobbs compared to the prior reproductive legal climate. While longer-term data are needed, findings indicate that men are invested in maintaining reproductive autonomy for themselves and their partners.

The Diversity of Vasectomy Reversal Providers and Their Web-based Advertising Habits in the United States.

OBJECTIVE: To better understand the internet advertising material published on clinician websites for the 30,000 men who undergo evaluation for vasectomy reversal (VR), which is a technically demanding procedure requiring microsurgical expertise. METHODS: Internet search trends for "vasectomy" and "vasectomy reversal" from 2004 to 2022 were assessed using Google Trends. Search engines were then queried on a state-by-state basis for physicians performing VR and the available information aggregated and analyzed using standard statistical approaches. RESULTS: VR search volume consistently represented roughly one-tenth of the search volume for vasectomy. One hundred and ninety reversal clinics were identified in 44 of 50 states with the highest number identified in the southeast region and an overall median price of $6500. Ninety percent of physicians were male and completed residencies in urology. Other specialties included obstetrics and gynecology, general surgery, family medicine and orthopedic surgery. Forty-two percent of urologists had completed infertility fellowships. Sixty percent of physicians utilized a microscope, and 4.7% of physicians explicitly stated they did not perform vasoepididymostomy even when indicated. Fifty two percent of clinics reported VR success rates as high as 100%, and 34% of clinics reported pregnancy outcomes. Twenty-five percent of clinics reported out-of-pocket VR pricing and 26% discussed possible complications. CONCLUSION: VR is a technically demanding cash-pay procedure being performed by physicians with a wide array of backgrounds and outcomes. Urologists should strive to lead by example and report their training, personal experiences, and expected outcomes to enable optimal medical decision making for each patient.

Discordant Bilateral Testicular Pathology Does not Affect Sperm Retrieval Rate in Bilateral Microdissection Testicular Sperm Extraction (mTESE).

OBJECTIVE: To assess the incidence of discordant testicular pathology in men undergoing bilateral microdissection testicular sperm extraction (mTESE) and association with sperm retrieval rate. METHODS: We performed a retrospective single-institutional review of all patients undergoing mTESE from 2007 to 2021 and aggregated clinical history, physical exam, semen analysis, and operative findings. Specimens with discordant pathology were re-reviewed by an experienced genitourinary.ßpathologist and categorized in a standardized fashion. Data were analyzed using SPSS. RESULTS: One hundred fourteen non-obstructive azoospermia.ßmen undergoing 132 mTESEs were identified within the study period. Eighty-five percent (112/132) of cases had pathology specimens available, and within this specific cohort the success rate was 41.9% (47/112). A total of 206 pathological reports resulted including 52.4% Sertoli cell only, 4.9% Leydig cell hyperplasia, 8.7% fibrosis, 16.5% maturation arrest, and 17.5% hypospermatogenesis. Twelve percent of testicles had more than 1 pathologic diagnosis. Sixty-six men had synchronous bilateral testicular pathology, and 11/66 (16.6%) had at least partially discordant pathology on initial review. Focused re-review by a genitourinary pathologist confirmed exclusively discordant pathology in 7/66 (10.6%) cases, with a sperm retrieval rate of 57% (4/7). The sperm retrieval rate.ßin men with discordant pathology was not significantly different from those with concordant pathology. CONCLUSION: Over 1 in 10 men undergoing mTESE may have discordant pathology between testicles, though this may not affect sperm retrieval rate.ßat the time of procedure. Clinicians should consider submitting bilateral testicular specimens for pathology to (1) clarify their outcomes data, and (2) assist with clinical decision-making and surgical planning if a repeat mTESE is indicated.

Novel sperm chromatin dispersion test with artificial intelligence-aided halo evaluation: A comparison study with existing modalities.

BACKGROUND: Sperm chromatin dispersion test is a common and inexpensive technique to assess sperm DNA fragmentation, but its subjectivity in assessing a small number of spermatozoa is a disadvantage. OBJECTIVES: To study the efficacy of a new sperm chromatin dispersion test kit (R10) combined with an artificial intelligence-aided halo-evaluation platform (X12) and compare the results to those of existing sperm DNA fragmentation testing methods. MATERIALS AND METHODS: Semen samples from normozoospermic donors (n = 10) and infertile men with abnormal semen parameters (n = 10) were enrolled. DNA fragmentation indices were examined by multiple assays, including R10, Halosperm G2 (G2), sperm chromatin structure assay, and terminal deoxynucleotidyl transferase deoxynucleotidyl transferase nick end labeling. In R10 assay, the DNA fragmentation indices were obtained both manually (manual R10) and by X12 (AI-R10). The obtained DNA fragmentation indices were analyzed by agreement analyses. RESULTS: The DNA fragmentation indices obtained by manual R10 and those obtained by AI-R10 showed a strong significant correlation (r = 0.97, p < 0.001) and agreement. The number of spermatozoa evaluated by AI-R10 was 2078 (680-5831). The DNA fragmentation indices obtained by manual R10 and AI-R10 both correlated with those of G2 (r = 0.90, p < 0.001; r = 0.88, p < 0.001). Between the AI-R10 and G2 results, Passing-Bablok regression showed no systematic or proportional difference, and Bland-Altman plots revealed overall agreement and a mean bias of 6.3% with an SD of 6.9% (95% limit of agreement: -7.2% to 19.9%). AI-R10 and sperm chromatin structure assays showed systematic differences with a mean bias of -1.9%, while AI-R10 and terminal deoxynucleotidyl transferase deoxynucleotidyl transferase nick end labeling revealed proportional differences with a mean bias of -10.7%. CONCLUSIONS: The novel sperm chromatin dispersion kit and artificial intelligence-aided platform demonstrated significant correlation and agreement with existing sperm chromatin dispersion methods by assessing greater number of spermatozoa. This technique has the potential to provide a rapid and accurate assessment of sperm DNA fragmentation without technical expertise or flow cytometry.

Testosterone and luteinizing hormone predict semen parameter improvement in infertile men treated with anastrozole.

OBJECTIVE: To identify patient factors associated with a clinically significant improvement in semen parameters among infertile men treated with the aromatase inhibitor anastrozole. DESIGN: Multi-institutional retrospective cohort study. SETTING: Two Tertiary Academic Medical Centers. PATIENTS: A total of 90 infertile men treated at 2 tertiary academic medical centers who met inclusion criteria and obtained pretreatment and posttreatment semen analyses. INTERVENTION: Prescription of anastrozole (median 3 mg/wk). MAIN OUTCOME MEASURES: Upgrade in the World Health Organization sperm concentration category (WHO-SCC). Univariate logistic regression, multivariable logistic regression, and partitioning analyses were performed to identify statistically significant patient factors capable of predicting treatment response. RESULTS: With anastrozole treatment, 46% (n = 41/90) of men responded favorably with a WHO-SCC upgrade, and 12% (n = 11/90) experienced a downgrade. Responders exhibited lower pretreatment levels of luteinizing hormone (LH, 4.7 vs. 8.3 IU/L) and follicle-stimulating hormone (4.7 vs. 6.7 IU/mL), higher pretreatment levels of testosterone (T, 356 vs. 265 ng/dL), and similar baseline level of estradiol (E2, 73% vs. 70% with detectible level). Baseline semen parameters differed, with anastrozole responders demonstrating higher baseline semen concentration (3.6 vs. 0.3 M/mL) and higher total motile sperm counts (3.7 vs. 0.1 M). Anastrozole therapy converted 29% (n = 26/90) of the cohort to normozoospermia and enabled intrauterine insemination access in 31% (n = 20/64) of previously ineligible patients. Interestingly, neither body mass index nor the baseline E2 level or E2-T ratio was associated with WHO-SCC upgrade. Multivariable logistic regression revealed the T-LH ratio (odds ratio: 1.02, 95% confidence interval: 1.00-1.03) and baseline nonazoospermia (odds ratio: 9.4, 95% confidence interval: 1.1-78.9) to be statistically significant predictors of WHO-SCC upgrade (area under receiver operating characteristic curve: 0.77). The final user-friendly partitioning model consisting of the T-LH ratio ≥100 and baseline non-azoospermia was 98% sensitive and 33% specific for WHO-SCC upgrades (area under the curve: 0.77). CONCLUSION: Anastrozole therapy decreases serum E2 levels, increases serum gonadotropins, and clinically improves semen parameters in half of men with idiopathic infertility. Nonazoospermic infertile men with T-LH ratios ≥100 are likely to benefit from anastrozole treatment irrespective of baseline E2 level or E2-T ratio. Men with azoospermia rarely respond to anastrozole and should be counseled on alternative treatments.