Erectile dysfunction is a multidimensional but common male sexual dysfunction that involves an alteration in any of the components of the erectile response, including organic, relational and psychological. Roles for nonendocrine (neurogenic, vasculogenic and iatrogenic) and endocrine pathways have been proposed. Owing to its strong association with metabolic syndrome and cardiovascular disease, cardiac assessment may be warranted in men with symptoms of erectile dysfunction. Minimally invasive interventions to relieve the symptoms of erectile dysfunction include lifestyle modifications, oral drugs, injected vasodilator agents and vacuum erection devices. Surgical therapies are reserved for the subset of patients who have contraindications to these nonsurgical interventions, those who experience adverse effects from (or are refractory to) medical therapy and those who also have penile fibrosis or penile vascular insufficiency. Erectile dysfunction can have deleterious effects on a man's quality of life; most patients have symptoms of depression and anxiety related to sexual performance. These symptoms, in turn, affect his partner's sexual experience and the couple's quality of life. This Primer highlights numerous aspects of erectile dysfunction, summarizes new treatment targets and ongoing preclinical studies that evaluate new pharmacotherapies, and covers the topic of regenerative medicine, which represents the future of sexual medicine.

Erectile dysfunction (ED) is an important health concern that can significantly affect a man's psychosocial well-being. ED has traditionally been considered a disease of old age; however, contemporary evidence suggests a growing incidence of ED in men younger than 40 years. The process of achieving an erection is multifaceted; there are many potential mechanisms that can be disrupted. It is critical to identify the specific causes of ED before proceeding with potentially costly and invasive therapeutic options. Advances in diagnostic and treatment modalities offer opportunities to identify and manage young men with ED. To provide an update on the prevalence and risk factors of ED in young men and to provide a framework to guide clinicians in identifying and managing the affected young man. Comprehensive review of the literature pertaining to ED in young men. ED in young men was assessed by outlining the prevalence according to recent epidemiologic studies. The pathophysiology, diagnostic considerations, risk factors, and etiologies were reviewed. Large multinational studies have estimated the prevalence of ED in young men to be as high as 30%. Several studies have stratified the etiologies of ED into psychogenic and organic causes. Psychogenic etiologies of ED include depression, anxiety, and partner-related difficulties. These patients tend to experience sudden onset of symptoms, with decreased libido and good quality of spontaneous or self-stimulated erections. Organic etiologies include vasculogenic, endocrinologic, neurogenic, iatrogenic, and structural components. These patients usually experience gradual onset of symptoms and a low to normal libido. Conservative treatments such as phosphodiesterase type 5 inhibitors continue to be the mainstay treatment. ED in young men is an increasingly common condition. A careful diagnostic evaluation should focus on the identification of any underlying etiology to ensure appropriate management of patients. Nguyen HMT, Gabrielson AT, Hellstrom WJG. Erectile Dysfunction in Young Men-A Review of the Prevalence and Risk Factors. Sex Med Rev 2017;5:508-520.

The etiologies of erectile dysfunction (ED) after nerve‐sparing radical prostatectomy have not been clearly elucidated. The aim of this study was to evaluate the effects of cavernous nerve injury on cavernous fibrosis, and to consider measures to prevent irreversible damage to the cavernous tissues. Twenty male Sprague‐Dawley rats constituted the study population. The animals were divided into 2 groups; group 1 consisted of sham‐operated rats (n = 10), and group 2 consisted of rats that underwent incision of both cavernous nerves (n = 10). Three months later, all rats underwent intracavernous papaverine injection (300 and 600 mg), and intracorporal pressures were recorded. Transforming growth factor‐β₁ (TGF‐β₁) messenger RNA (mRNA) expression from rat penile tissue was measured using reverse transcriptase‐polymerase chain reaction. Hypoxia‐inducible factor‐1α (HIF‐1α), TGF‐β₁, and collagen I and III protein expressions were determined by Western blot analysis and immunohistochemical staining. Erectile function as studied with intracavernosal papaverine injection and histological analysis of penile cross‐sections at 3 months was similar in both groups. TGF‐β₁ mRNA expression, HIF‐1α, TGF‐β₁, and collagen I and III protein expressions were significantly greater in the neurotomy group. Immunohistochemical staining for TGF‐β₁, HIF‐1α, and collagen III were qualitatively more positive in the neurotomy group, whereas collagen I staining was similar. This study demonstrates an increase in TGF‐β₁, HIF‐1α, and collagen III synthesis in rat cavernosal smooth musculature after cavernous neurotomies. In theory, cavernous fibrosis may be reduced by employing various vasoactive agents or interventions that increase oxygenation to the corporal tissues during the postoperative period.

We investigated the efficacy and safety of intralesional interferon alpha-2b for the treatment of Peyronie's disease. A total of 117 consecutive patients with a mean age of 55.1 years who had Peyronie's disease were enrolled in a single-blind, multicenter, placebo controlled, parallel study to determine the efficacy and safety of intralesional interferon alpha-2b therapy (Schering, Kenilworth, New Jersey), including 62 who received placebo and 55 who received interferon alpha-2b. Saline (10 ml) in controls and interferon alpha-2b (5 x 10(6) U) were administered biweekly for 12 weeks. Each patient was evaluated for penile curvature, plaque size and density, penile pain, erectile function and penile hemodynamics before and after study completion. Improvement in these parameters was statistically compared between the groups. A total of 53 patients in the control arm and 50 in the interferon alpha-2b arm completed the study. Improvement in penile curvature, plaque size and density, and pain resolution was significantly greater in patients treated with interferon alpha-2b vs placebo. The increase in mean International Index of Erectile Function scores was not significantly different between the groups. Penile blood flow improvement was observed in interferon alpha-2b treated patients but not in those who received placebo. The decrease in the number of penile vascular pathologies was significantly higher in interferon alpha-2b cases. Side effects, mostly flu-like symptoms, which were frequently noted in patients on interferon alpha-2b, were mild to moderate in degree and of short duration. This single-blind, multicenter, placebo controlled, parallel study demonstrates that intralesional interferon alpha-2b at a dose of 5 x 10(6) units biweekly for 12 weeks is effective and safe as minimally invasive therapy for Peyronie's disease.