Recent insights into androgen action on the anatomical and physiological substrate of penile erection

Narrative review: pathogenesis, diagnosis, and treatment of sleep-related painful erection

Objective

Through critical analysis and comprehensive review of the limited literature, this paper can help clinicians better identify the pathophysiology of sleep-related painful erections (SRPE) and provide direction for future treatment research.

Background

Patients with SRPE will be awakened by painful erections during sleep, which affects their sleep process and general health. At present, literatures of experimental and clinical research on SRPE disease are limited, as well as long-term reports on its pathogenesis and clinical management.

Methods

We use the PubMed database to obtain sleep-related peer erection literature. The search terms used include sleep, painful, penis and erection. After rigorous screening, the search returned 21 references published between 1987 and 2021.

Conclusions

The main cause of SRPE is obstructive sleep apnea (OSA) syndrome, psychological and spiritual factors, androgen elevation, neuroendocrine regulation and threshold of pain in the REM phase. The combination of multiple medications is the most effective approach to treat sleep-pain-related erections. The combination of CPAP, REM inhibitors and Baclofen has significant effect on SRPE caused by OSA syndrome. This article provides effective support and strategies for doctors to manage SRPE patients through a comprehensive analysis of the pathogenesis mechanism and clinical treatment strategies of SRPE.

Estradiol-Testosterone Imbalance Is Associated with Erectile Dysfunction in Patients with Klinefelter Syndrome

Erectile dysfunction (ED) is a frequent sexual disorder in adult men. Klinefelter syndrome (KS) is the most common sex chromosomal disorder and a frequent cause of male hypogonadism. Psychological and cognitive aspects are quite typical in KS and have been linked to ED, while the role of testosterone (T) levels in sexual function of KS subjects has not been fully elucidated. The purpose of the present study is to investigate the role of hormonal disturbances in erectile function of subjects with KS. We conducted a retrospective study involving 52 Klinefelter patients newly diagnosed who never received androgen replacing therapy. All the subjects underwent medical history, accurate physical examination, and blood tests. The International Index of Erectile Function questionnaire (IIEF-EF) score correlated negatively with estradiol/testosterone ratio (E2/T); this correlation remained statistically significant after correction for age (ρ −0.320 p = 0.018). A multiple linear regression analysis identified age and E2/T as the main predictors of IIEF-EF score (R2 0.169 F = 3.848 p = 0.008). Our findings corroborate previous KS data obtained in the general population showing an association between higher E2/T ratio and impaired erectile function. Larger studies are required to better elucidate the pathophysiology of ED in patients with KS.

Beneficial Effects of Human Umbilical Cord Blood Mononuclear Cells on Persistent Erectile Dysfunction After Treatment of 5-Alpha Reductase Inhibitor in Rats

BACKGROUND

Effects of human umbilical cord blood (HUCB) as a valuable source for stem cell-based therapies have not been studied in persistent post-5-alpha reductase inhibitors (5ARI) erectile dysfunction (PPED).

AIM

To determine the effect of intracavernosal injection of HUCB mononuclear cells (MNCs) on ED associated with dutasteride treatment.

METHODS

Twenty five adult male Sprague-Dawley rats were divided into 5 groups (n = 5 per group): (i) control, (ii) 8-week dutasteride (0.5 mg/kg/day, in drinking water), (iii) 12-week dutasteride, (iv) 8-week dutasteride+HUCB-MNCs (1 × 10⁶) and (v) 12-week dutasteride+HUCB-MNCs. HUCB-MNCs were administered intracavernosally after eight weeks of dutasteride treatment. Experiments were performed at 4 weeks following the injection of HUCB-MNCs. Erectile responses and isometric tension of corpus cavernosum (CC) were measured. The protein expressions of phosphodiesterase type 5 (PDE5), endothelial nitric oxide synthase (eNOS), neuronal NOS (nNOS), hypoxia-inducible factor (HIF)-1α and smooth muscle/collagen contents in penile tissue were evaluated by Western blotting, immunohistochemistry, and Masson's trichrome staining, respectively.

MAIN OUTCOME

In vivo erectile function, in vitro relaxant and contractile responses of CC, protein expression and localization of PDE5, eNOS, nNOS, HIF-1α, and smooth muscle content in penile tissue.

RESULTS

Erectile responses in the dutasteride-treated groups were significantly decreased compared with controls (P < .001), persisting after 4-wk of washout. HUCB-MNCs restored diminished intracavernosal pressure responses, acetylcholine-, sodium nitroprusside-, sildenafil-induced relaxations, and increased phenylephrine and electrical field stimulation (EFS)-induced contractions. Decreased EFS-induced relaxations in dutasteride-treated groups were not restored by HUCB-MNCs. Increased PDE5 and reduced nNOS expressions in dutasteride groups were restored by HUCB-MNCs in the 12-week dutasteride group. eNOS and HIF-1α protein expression and serum total and free testosterone  levels were similar among groups. HUCB-MNCs reversed the decreased smooth muscle/collagen ratio in dutasteride-treated tissues. There was a significant increase in PDE5 and HIF-1α staining in 8-week dutasteride animals.

CLINICAL TRANSLATION

This study demonstrates the corrective potential of HUCB-MNCs on some persistent structural and functional deterioration caused by 5ARI treatment in rats, which may encourage further evaluation of HUCB-MNCs in men with PPED.

STRENGTHS AND LIMITATIONS

Therapeutic application of intracavernosal HUCB-MNCs is a novel approach for the rat model of post-5ARI ED. Lack of serum and tissue dihydrotestosterone measurements, vehicle injections and characterization of the cells remain limitations of our study.

CONCLUSION

The persistent ED after prolonged administration of dutasteride in rats is reversed by HUCB-MNC treatment, which holds promise as a realistic therapeutic modality for this type of ED. Oztekin CV, Yilmaz-Oral D, Kaya-Sezginer E, et al. Beneficial Effects of Human Umbilical Cord Blood Mononuclear Cells on Persistent Erectile Dysfunction After Treatment of 5-Alpha Reductase Inhibitor in Rats. J Sex Med 2021;18:889-899.

Estradiol correlates with erectile dysfunction and its severity in type 2 diabetic patients

AIMS

Erectile dysfunction (ED) is a frequent microvascular complication of type 2 diabetes mellitus (T2DM). Hormonal derangements such as hypogonadism and hyperestrogenism are common in T2DM. Our aim was to investigate the relationship between estrogens and ED in diabetic patients.

METHODS

We performed a retrospective study on 57 patients with T2DM suffering from ED. ED was assessed with the International Index of Erectile Function questionnaire (IIEF-5) and penile color-doppler ultrasound (PCDU). Blood tests included glycated hemoglobin, lipid profile, total testosterone (T), and estradiol (E2).

RESULTS

E2 was negatively correlated with IIEF-5 score after correction for age, diabetes duration, BMI, HbA1c, LDL- and HDL-cholesterol, T and PSA (r = -0.457, p < 0.01). Patients in the higher E2 quartile, had statistically higher probability of severe ED (61.5%). In the same patients, the PCDU demonstrated a statistically longer Acceleration Time (120.0 ± 24.5, p = 0.048) indicating an impaired arterial flow.

CONCLUSIONS

In diabetic patients, higher E2 is associated with worse erectile function and impaired cavernous arterial flow. Diabetic patients with high E2 are more prone to severe ED. It could be suggested to include estradiol measurement in the hormonal assessment of ED in patients with T2DM.

Effect of tadalafil on penile nitric oxide synthase and corporal smooth muscle in rats under dutasteride treatment

Aim: To investigate the effect of tadalafil in rats administered with daily dutasteride.Methods: Twenty-four Sprague-Dawley male rats were allocated to three groups as control (group C), dutasteride (group D) and dutasteride plus tadalafil (group D + T). After a month of treatment, serum samples were obtained from rats to measure dihydrotestosterone and total testosterone. Nitric oxide (NO) synthase (NOS) immunoreactivity and levels of NOS enzyme isoforms, NO and cyclic guanosine monophosphate (cGMP) were evaluated in the harvested penile tissues. Also, corporal smooth muscle and collagen were examined.Results: Staining intensities of neuronal NOS and endothelial NOS were significantly lower in group D (p < .05). They were similar between group C and group D + T. Immunoreactivity of inducible NOS was observed higher in group D than group C (p  =  .01) whereas group D + T had the highest iNOS (p<.001). ELISA revealed similar outcomes in terms of NOS enzyme isoform levels. The mean of smooth muscle to collagen ratio was the lowest in group D (p < .001) and it was similar among group C and group D + T (p = .072). Group D had the lowest cGMP and NO levels (p  <  .05) and they did not differ between group C and group D + T (p>.05). Group D and group D + T had significantly decreased dihydrotestosterone and increased testosterone, compared to group C (p < .001). They were similar between group D and group D + T.Conclusion: Daily treatment with tadalafil improves dutasteride-induced changes in rat penis.

Importance of Different Grades of Abdominal Obesity on Testosterone Level, Erectile Dysfunction, and Clinical Coincidence

The aim of the current study was to investigate the influence of different grades of abdominal obesity (AO) on the prevalence of testosterone deficiency syndrome (TDS), erectile dysfunction (ED), and metabolic syndrome (MetS). In a cross-sectional descriptive study, a total of 216 males underwent a complete urological, internal, and hormonal evaluation. Males were divided according to waist circumference into five groups: less than 94 cm (Grade [G] 0), 94 to 101 cm (G1), 102 to 109 cm (G2), 110 to 119 cm (G3), and more than 120 cm (G4). Incidence of ED, TDS, and MetS was compared in these groups and in participants without AO. Some degree of ED was identified in 74.7% of males with AO. In G1, there were 61% of males with ED, in G2 68%, in G3 83%, and in G4 87%. A strong correlation between testosterone (TST) level and AO was identified. Ninety-eight out of 198 (49.5%) males with AO and 1/18 (5.5%) males without AO had TDS. There were significant differences between individual groups. In the group of males with AO G4 (more than 120 cm), 87.1% had TDS. MetS was diagnosed in 105/198 (53.0%) males with AO, but in G4, 83.9% of males with AO had MetS. Males older than 40 years of age with AO have a higher incidence of ED, TDS, and MetS. Dividing males into five groups according to waist circumference seems to be reasonable. With growing AO, there were significantly more males with ED, TDS, and MetS.

Impact of the association between elevated oestradiol and low testosterone levels on erectile dysfunction severity

Our aim was to assess the impact of the association between elevated oestradiol (E2) and low testosterone (T) levels on erectile dysfunction (ED) severity. A total of 614 male patients with ED and a normal or low T level in association with normal or elevated E2 levels were enrolled. Patients underwent routine laboratory investigations in addition to measurements of total T, total E2, follicle-stimulating hormone (FSH), luteinizing hormone (LH) and prolactin. We compared the responses to the erectile function domain, Q3 (achieving erection) and Q4 (maintaining erection) of the International Index for Erectile Function (IIEF) score in patients with the following: normal T and E2 levels; low T level; low T level and elevated E2 level; and elevated E2 level. Of the patients included, 449 (73.1%) had normal T and E2 levels, 110 (17.9%) had a low T level, 36 (5.9%) had a low T level and an elevated E2 level, and 19 (3.1%) had an elevated E2 level. Increased ED severity was significantly associated with low T levels, elevated E2 levels, and both a low T level and an elevated E2 level. Additionally, the mean values of the EF-domain, Q3 and Q4 were significantly lower in patients with both a low T level and an elevated E2 level compared to patients with any condition alone. In conclusion, a low T level had the primary effect on erectile function; however, a concomitantly elevated E2 level had an additive impairment effect.

Occurrence of erectile dysfunction, testosterone deficiency syndrome and metabolic syndrome in patients with abdominal obesity. Where is a sufficient level of testosterone?

AIM

The aim of this study was to determine the prevalence of erectile dysfunction (ED), testosterone deficiency syndrome (TDS), and metabolic syndrome in patients with abdominal obesity (AO) and the prevalence of morbidity at different levels of testosterone (TST).

BACKGROUND

Male sex hormones play an important role in ED and variety of TDS and may have influence on the development of metabolic syndrome. The number of men with AO which constitutes a serious health risk is continuously growing. Currently, there are different views that TST levels are already insufficient, and the patient should benefit from treatment.

OBJECTIVES

This study examined the association between ED, testosterone level and metabolic syndrome in men with AO.

DESIGN, SETTING, AND PARTICIPANTS

The study was carried out in an outpatient urology center of Urology Clinic and Obesity Center of the Clinic of Internal Medicine. There were 167 participants—men with AO which were examined as part of preventive examination.

METHODS

Hormonal, a complete urological and internal evaluation was carried out in every patient.

RESULTS AND LIMITATIONS

We found some degree of ED in 73% (122/167) in men with AO. The TST levels below 14 nmol/l had of these 122 patients 84 patients (68.9%) and 49 patients (40.2%) below 10 nmol/l. In this group of patients, we found 103/167 patients (61.7%) with metabolic syndrome. When we compared TST level and morbidity, we found significantly more patients with diabetes mellitus (DM), hypertension and dyslipidemia in group with TST below 10 nmol/l. We also found difference in the levels of HDL cholesterol and triglycerides in the group of patients with TST 10–14 and over 14 nmol/l.

CONCLUSION

Patients over 40 years of age with AO and ED should also be examined for TDS and metabolic syndrome. In this group of patients we found that 113/167 patients (67.6%) had total TST below 14 nmol/l, and sufficient level of TST seems to be above this level.

Incomplete recovery of erectile function in rat after discontinuation of dual 5-alpha reductase inhibitor therapy

AIM

The association of 5-alpha reductase inhibitor (5ARI) therapy and sexual dysfunction has been reported. Some patients claim persistent erectile dysfunction despite long-term discontinuation of 5ARI treatment. The aim of this study was to assess erectile function after cessation of 5ARI therapy using a rat model.

METHODS

Twenty-six adult male Sprague-Dawley rats were randomized into three groups: (i) control (N = 10); (ii) 8-week dutasteride treatment (0.5 mg/rat/day, in drinking water, N = 8); and (iii) 6-week dutasteride treatment followed by a 2-week washout period (N = 8). The experiments were performed after 8 weeks from the initiation of treatment in all groups. In vivo erectile activity and in vitro contractile and relaxant responses of cavernosal smooth muscle were investigated.

RESULTS

In vivo erectile activity (intracavernosal pressure [ICP]/mean arterial pressure [MAP] and total ICP) in treatment groups were significantly decreased compared with controls (ICP/MAP: P < 0.001 for 2.5 v, 5 v, and 7.5 v; total ICP: P < 0.001 for 5 v and P < 0.01 for 7.5 v). Acetylcholine-induced relaxations were diminished in treatment groups (P < 0.05). Relaxant responses to electrical field stimulation (EFS) were decreased in the 8-week treatment group (P < 0.05) but were similar to controls in the washout group. Sodium nitroprusside (SNP)-induced endothelium-independent relaxations were reduced in the 8-week dutasteride treatment group (P < 0.01), while these responses were restored in the washout group. The contractile responses to the alpha1-adrenergic agonist phenylephrine were decreased in treatment groups compared with controls (P < 0.01). Direct neurogenic contractile responses in the dutasteride groups were significantly lower than controls between 1 and 15 Hz frequencies (but not at 20 Hz) and washout partially restored the responses at 10 and 15 Hz.

CONCLUSION

Discontinuation of dutasteride improved the relaxant responses to EFS and SNP, while cholinergic and adrenergic responses remained depressed. Our findings suggest a time-dependent detriment of dutasteride on erectile function. The withdrawal/washout effect of 5ARIs on parameters of human sexual function warrants further investigation.

Effect of testosterone and frequent low-dose sildenafil/tadalafil on cavernous tissue oxidative stress of aged diabetic rats

This study aimed to assess the effect of testosterone (T) administration and chronic low-dose sildenafil/tadalafil on cavernous tissue oxidative stress (OS) of aged diabetic rats. In all, 140 Sprague-Dawley aged rats were subdivided into the following: controls; streptozotocin (STZ)-induced diabetic rats; diabetic rats injected with T every 4 weeks; diabetic rats on sildenafil orally daily; diabetic rats on T and daily sildenafil; diabetic rats on tadalafil orally every other day; diabetic rats on T and tadalafil; diabetic rats on alternate sildenafil/tadalafil; and diabetic rats on alternate sildenafil/tadalafil with T. After 12 weeks, the rats were euthanised where in dissected cavernous tissues malondialdehyde (MAD), glutathione peroxidase (GPx) and cGMP (cyclic guanosine monophosphate) were estimated. Compared with controls, aged diabetic rats demonstrated significant increase in cavernous tissue MDA and significant decrease in GPx and cGMP where diabetic rats injected with T had marked improvement of these parameters. Diabetic rats on sildenafil, tadalafil or alternate sildenafil/tadalafil demonstrated significant increased cavernous tissue GPx, cGMP and decreased cavernous MDA that was further improved when supplemented with T. It is concluded that frequent low-dose use of sildenafil and/or tadalafil supplemented with T has a marked impact on ameliorating cavernous OS in aged diabetic rats.

Mechanisms of penile erection and basis for pharmacological treatment of erectile dysfunction

Erection is basically a spinal reflex that can be initiated by recruitment of penile afferents, both autonomic and somatic, and supraspinal influences from visual, olfactory, and imaginary stimuli. Several central transmitters are involved in the erectile control. Dopamine, acetylcholine, nitric oxide (NO), and peptides, such as oxytocin and adrenocorticotropin/α-melanocyte-stimulating hormone, have a facilitatory role, whereas serotonin may be either facilitatory or inhibitory, and enkephalins are inhibitory. The balance between contractant and relaxant factors controls the degree of contraction of the smooth muscle of the corpora cavernosa (CC) and determines the functional state of the penis. Noradrenaline contracts both CC and penile vessels via stimulation of α₁-adrenoceptors. Neurogenic NO is considered the most important factor for relaxation of penile vessels and CC. The role of other mediators, released from nerves or endothelium, has not been definitely established. Erectile dysfunction (ED), defined as the "inability to achieve or maintain an erection adequate for sexual satisfaction," may have multiple causes and can be classified as psychogenic, vasculogenic or organic, neurologic, and endocrinologic. Many patients with ED respond well to the pharmacological treatments that are currently available, but there are still groups of patients in whom the response is unsatisfactory. The drugs used are able to substitute, partially or completely, the malfunctioning endogenous mechanisms that control penile erection. Most drugs have a direct action on penile tissue facilitating penile smooth muscle relaxation, including oral phosphodiesterase inhibitors and intracavernosal injections of prostaglandin E₁. Irrespective of the underlying cause, these drugs are effective in the majority of cases. Drugs with a central site of action have so far not been very successful. There is a need for therapeutic alternatives. This requires identification of new therapeutic targets and design of new approaches. Research in the field is expanding, and several promising new targets for future drugs have been identified.

Correlation between serum total testosterone and the AMS and IIEF questionnaires in patients with erectile dysfunction with testosterone deficiency syndrome

PURPOSE

This study was conducted to investigate the relationship between serum total testosterone levels and scores on the Aging Male's Symptom (AMS) scale and the International Index of Erectile Function (IIEF) in men with erectile dysfunction with testosterone deficiency syndrome (TDS).

MATERIALS AND METHODS

From January 2005 to July 2008, 134 patients who complained of sexual dysfunction such as erectile dysfunction or decreased libido as the main symptoms of TDS with serum total testosterone levels less than 3.5 ng/ml were evaluated by independent t-test and linear regression analysis, respectively. Patients with treated hypogonadism within 6 months, with a history of taking a PDE5 inhibitor or an antidepressant for a depressive disorder, or who had metabolic syndrome were excluded from this study.

RESULTS

The AMS scale and its 3 subdomain scores were not significantly correlated with the total testosterone level. By contrast, the total IIEF score and the score of each IIEF domain except sexual desire showed a weakly significantly positive correlation with serum total testosterone.

CONCLUSIONS

In TDS patients with erectile dysfunction, there was a low relationship between serum total testosterone levels and the AMS scale and a weakly positive correlation between total testosterone levels and all IIEF domains except sexual desire. There was a low relationship between the AMS scale, the sexual desire domain score of the IIEF, and total testosterone. We should understand these limitations when evaluating patients with erectile dysfunction with TDS. New scales should be developed for the evaluation of erectile dysfunction in these patients.

Testostérone et contrôle central de l’érection

La testostérone orchestre l’organisation périnatale et l’activation adulte des structures nerveuses cérébrales et spinales impliquées dans l’expression du comportement sexuel mâle. Cette revue décrit brièvement les différents effets de la testostérone dans la régulation de la motivation sexuelle et de l’érection, et les modèles génétiques générés, jusqu’à présent, dans le but d’élucider ses mécanismes d’action centraux.

Testosterone undecanoate in the treatment of male hypogonadism

IMPORTANCE OF THE FIELD

Testosterone undecanoate (TU) represents an exciting new testosterone replacement therapy for hypogonadal men due to its convenient dosing schedule and favorable pharmacokinetic and safety profiles.

AREAS COVERED IN THIS REVIEW

Clinical, pharmacokinetic and safety characteristics of TU will be reviewed. The characteristics of currently approved testosterone therapies will be reviewed and compared with those of TU in order to determine which therapy most appropriately meets the clinical objective of properly matching a patient with a therapy that is best able to deliver physiological levels of testosterone for prolonged periods of time, while at the same time being safe, effective, inexpensive, simple to use, and with few side effects.

WHAT THE READER WILL GAIN

TU represents the first long-acting injectable with an excellent safety profile that can be administered only four times annually to produce stable levels of testosterone. Long-term studies have validated the clinical efficacy of TU in maintaining therapeutic levels of testosterone. Patient preference for the convenient dosing schedule might also lead to better compliance and therapeutic benefit. No serious side effects have been noted with the use of TU, including long-term data on patients treated with TU over 8 years.

TAKE HOME MESSAGE

TU is both a desirable and safe option for the treatment of hypogonadal men. Patients will benefit from the stable testosterone levels and fewer required injections, while achieving the desired benefits of androgen replacement.

Short term testosterone replacement therapy improves libido and body composition

OBJECTIVE

To assess the efficacy and safety of testosterone replacement in males with late-onset hypogonadism compared to hypogonadal men without replacement, and controls, during six months.

METHODS

We assessed, through ADAM, AMS, IIEF-5 and SF-36 questionnaires, and through clinical and laboratory examinations, 62 patients divided into three groups: 17 hypogonadal males (HR) used intramuscular testosterone every three weeks; 14 hypogonadal males (HV) and 31 non-hypogonadal males (CV) used oral vitamins daily.

RESULTS

When compared to others, HR group obtained libido improvement assessed by ADAM 1 (p = 0.004), and borderline sexual potency improvement assessed by IIEF-5 (p = 0.053), besides a decrease in waist circumference after eight weeks (p = 0.018). The remaining parameters did not differ between the groups. PSA and hematocrit remained stable in those using testosterone.

CONCLUSION

Six months of testosterone replacement improved sexuality and body composition, with prostatic and hematological safety.

Testosterone and chronic sildenafil/tadalafil anti-apoptotic role in aged diabetic rats

This work aimed to assess the cavernous anti-apoptotic role of using chronic low-dose sildenafil/tadalafil with and without testosterone (T) in aged diabetic rats. In all, 140 Sprague-Dawley aged rats were divided into the following groups: controls; induced diabetic rats; diabetic rats that received intramuscular depot T once every 4 weeks; diabetic rats on sildenafil 2 mg kg(-1) orally daily; diabetic rats on T and daily sildenafil; diabetic rats on tadalafil 0.45 mg kg(-1) orally every other day; diabetic rats on every-other-day tadalafil and T; diabetic rats on alternate sildenafil and tadalafil; and diabetic rats on alternate sildenafil, tadalafil and T. After 12 weeks, Bax (apoptotic factor), Bcl(2) (B-cell lymphoma 2; anti-apoptotic factor), cGMP (cyclic guanosine monophosphate) were estimated in their cavernous tissues. Compared with the controls, aged diabetic rats showed significant increased cavernous tissue Bax and significant decreased Bcl(2), in which diabetic rats injected with T showed the reverse compared with the diabetic rats. Diabetic rats on sildenafil or tadalafil showed significant increased cavernous Bcl(2) and decreased Bax with upgraded Bcl(2)/Bax ratio that was improved being on T. Diabetic rats on alternate sildenafil/tadalafil with or without T showed further significant increased cavernous tissue Bcl(2) with upgraded Bcl(2)/Bax ratio. It is concluded that frequent low-dose use of sildenafil and/or tadalafil combined with T would be predicted to have a pronounced anti-apoptotic cavernous tissue effect on the cavernous tissues of aged diabetic rats.

Anatomy, physiology, and pathophysiology of erectile dysfunction

INTRODUCTION

Significant scientific advances during the past 3 decades have deepened our understanding of the physiology and pathophysiology of penile erection. A critical evaluation of the current state of knowledge is essential to provide perspective for future research and development of new therapies.

AIM

To develop an evidence-based, state-of-the-art consensus report on the anatomy, physiology, and pathophysiology of erectile dysfunction (ED).

METHODS

Consensus process over a period of 16 months, representing the opinions of 12 experts from seven countries.

MAIN OUTCOME MEASURE

Expert opinion was based on the grading of scientific and evidence-based medical literature, internal committee discussion, public presentation, and debate.

RESULTS

ED occurs from multifaceted, complex mechanisms that can involve disruptions in neural, vascular, and hormonal signaling. Research on central neural regulation of penile erection is progressing rapidly with the identification of key neurotransmitters and the association of neural structures with both spinal and supraspinal pathways that regulate sexual function. In parallel to advances in cardiovascular physiology, the most extensive efforts in the physiology of penile erection have focused on elucidating mechanisms that regulate the functions of the endothelium and vascular smooth muscle of the corpus cavernosum. Major health concerns such as atherosclerosis, hyperlipidemia, hypertension, diabetes, and metabolic syndrome (MetS) have become well integrated into the investigation of ED.

CONCLUSIONS

Despite the efficacy of current therapies, they remain insufficient to address growing patient populations, such as those with diabetes and MetS. In addition, increasing awareness of the adverse side effects of commonly prescribed medications on sexual function provides a rationale for developing new treatment strategies that minimize the likelihood of causing sexual dysfunction. Many basic questions with regard to erectile function remain unanswered and further laboratory and clinical studies are necessary.

The efficacy and safety of testosterone undecanoate (Nebido(®)) in testosterone deficiency syndrome in Korean: a multicenter prospective study

INTRODUCTION

Long-acting injectable testosterone undecanoate (TU, Nebido(®)), a new parenteral testosterone preparation, has recently been introduced to avoid frequent injections of the conventional injectable esters.

AIMS

To assess the efficacy and safety of long-acting injectable testosterone undecanoate (TU, Nebido(®)) in Korean patients with testosterone deficiency syndrome (TDS).

METHODS

One hundred thirty-three patients who complain of erectile dysfunction with serum testosterone level less than 3.5 ng/mL were injected with 1,000 mg of TU (4 mL/ample) on day 1, followed by another injection after 6 weeks and 18 weeks. For the safety profiles, serum hemoglobin (Hb), hematocrit (Hct), glucose, lipid profile, and prostate-specific antigen (PSA) were measured.

MAIN OUTCOME MEASURES

Body mass index (BMI) was measured at the time of the first visit and after 12, 24 weeks. Primary efficacy was evaluated according to changes in the International Index of Erectile Function (IIEF) from the initial visit to the final visit (24 weeks) and from the initial visit to each visit. Secondary efficacy was assessed with changes of the Aging Males' Symptoms (AMS) Scale and the Global Efficacy Question (GEQ) for improvement of erectile function.

RESULTS

Mean age of patients was 54 ± 9.6 years. Compared with pretreatment, no significant improvement in BMI was observed. Serum total testosterone and free testosterone were significantly increased at 12 weeks and were maintained until 24 weeks (P < 0.001). TU significantly decreased cholesterol (P < 0.0001). TU significantly improved total IIEF, all five domain scores of IIEF (P < 0.0001) and total AMS, all three domain scores of AMS (P < 0.0001). On GEQ, TU improved erectile function in 76.9% of subjects. On safety profile, TU significantly elevated Hb, Hct, and PSA at 24 weeks but within normal range. No serious adverse reactions were observed. Drop-out rate was 15.0%.

CONCLUSIONS

In this prospective multicenter study, TU was effective, safe, and tolerable until 24 weeks in Korean TDS patients. Further well-controlled, long-term study should follow.

Comparison of long-acting testosterone undecanoate formulation versus testosterone enanthate on sexual function and mood in hypogonadal men

OBJECTIVE

To compare the effects of two treatment modalities of testosterone on sexual functioning and mood. Design Forty men were randomized to receive either parenteral testosterone enanthate (TE) or long-acting parenteral testosterone undecanoate (TU) over a period of 30 weeks. Thereafter, 20 men who had received TU and 16 men who had received TE continued with TU and completed another 65 weeks to study longer-term effects of TU.

METHODS

The following variables of sexual functioning were studied: sexual thoughts and fantasy, sexual interest and desire, satisfaction with sex life, number of erections and ejaculations per week, and number of spontaneous morning erections per week. Also variables related to mood were analyzed.

RESULTS

Improvements in these variables were significant and were of a similar magnitude in the group treated with TU and TE for 30 weeks. Improvements were maintained at the same levels over a period of another 65 weeks when all men received TU. Effects on mood were recorded for 30 weeks, but were more difficult to establish in the study population. There were significant differences in baseline values between the two groups and scores showed wide s.d.

CONCLUSIONS

Both TE and TU were effective in improving sexual functions in hypogonadal men. An advantage of TU over TE is its lower frequency of administration and its better tolerability and safety profile.

Lower urinary tract symptoms and its potential relation with late-onset hypogonadism

The study of the health status of the aging male takes presently a more integrative approach and it appears that ailments typical of male aging, such as lower urinary tract symptoms (LUTS), (visceral) obesity, metabolic syndrome and erectile failure are significantly interrelated. A common denominator of the above ailments is lower-than-normal testosterone levels occurring in a significant proportion of elderly men. This review addresses the potential connections between LUTS and late-onset hypogonadism. In animal studies there appear to be androgen and estrogen receptors in the urothelium and smooth muscle cells of the urethra and bladder of the rat and rabbit, as well as in the neurons in the autonomic ganglia of the prostatic plexus of the male rat. Upon castration electrically evoked relaxations of the smooth muscle of the prostatic urethra were decreased. There is a Rho-kinase activation/endothelin pathway; possibly involved in the increased smooth muscle activity found in both LUTS/benign prostate hyperplasia. Nitric oxide (NO) appears to have a smooth muscle relaxing effect in the urogenital organs. Studies in humans have convincingly shown that phosphodiestererase inhibitors have a beneficial effect on LUTS. More intervention studies should be undertaken to test the clinical validity of the theoretically plausible interrelationship between LUTS and late-onset hypogonadism.

The triad of erectile dysfunction, hypogonadism and the metabolic syndrome

AIM

To identify the relationship of erectile dysfunction, hypogonadism and the metabolic syndrome in the context of men's health.

METHODS

An Expert Panel Meeting was held in December 2006 in Vienna, Austria. In addition a comprehensive literature search was conducted.

RESULTS

Men have a higher incidence of cardiovascular events than women of similar ages which has led to the belief that testosterone is a risk factor for cardiovascular disease in men. The latter hypothesis is no longer tenable. On the contrary, low testosterone levels are associated with (visceral) obesity, the metabolic syndrome, diabetes mellitus, cardiovascular disease and erectile dysfunction (ED). Testosterone therapy does not lead to an increased incidence of cardiovascular disease or events such as myocardial infarction, stroke or angina. Until recently (visceral) obesity, the metabolic syndrome, diabetes mellitus, cardiovascular disease and ED were viewed as more or less independent entities affecting the ageing male. It was not recognised that hypogonadism is a common denominator. With a more integrative approach to the health situation of middle-aged and elderly men, these conditions appear closely interrelated in their manifestations, hypothetically in their aetiology, diagnostic strategy and also their treatment.

CONCLUSION

Improving sexual health is a portal to identify health hazards and improving men's health. Appropriate diagnosis and medical work up of men presenting with sexual symptoms may have the benefit of the diagnosing and treating other important conditions, such as obesity, diabetes, hypertension and hyperlipidaemia.

Diagnosing and treating testosterone deficiency in different parts of the world. Results from global market research

AIM

This study analysed variations between different regions of the world in diagnosing and treating testosterone (T) deficiency.

METHODS

Physicians were interviewed in Germany, Spain and the United Kingdom, in Brazil, in Saudi Arabia and South Korea. Items in the survey: 1) reasons/motivation to use or not to use T; 2) what category of patients would not receive T on the basis of these concerns; 3) concerns about prostate pathology in the decision not to provide T treatment; 4) phosphodiesterase type 5 (PDE-5) inhibitors are efficacious, but T treatment makes a comeback.

RESULTS

Between 5% and 10% of consulting patients suffered from T deficiency. The fear to induce prostate cancer appeared very powerful. About 68% of physicians associate the use of T more with risks than benefits, more so in Europe than elsewhere. As a result about 35% of hypogonadal men do not receive treatment. The PDE-5 inhibitors are very prominent in the treatment of erectile dysfunction. Of patients suffering from erectile dysfunction, 18% to 29% have T deficiency which is not always diagnosed and treated.

CONCLUSION

World-wide physicians require more education on diagnosing T deficiency, on the role of T in erectile dysfunction and the relative safety of testosterone treatment.

The neurophysiology of sexual arousal

Our understanding of the process and initiation of sexual arousal is being enhanced by both animal and human studies, inclusive of basic science principles and research on clinical outcomes. Sexual arousal is dependent on neural (sensory and cognitive) factors, hormonal factors, genetic factors and, in the human case, the complex influences of culture and context. Sexual arousal activates the cognitive and physiologic processes that can eventually lead to sexual behavior. Sexual arousal comprises a particular subset of central nervous system arousal functions which depend on primitive, fundamental arousal mechanisms that cause generalized brain activity, but are manifest in a sociosexual context. The neurophysiology of sexual arousal is seen as a bidirectional system universal to all vertebrates. The following review includes known neural and genomic mechanisms of a hormone-dependent circuit for simple sex behavior. New information about hormone effects on causal steps related to sex hormones' nuclear receptor isoforms expressed by hypothalamic neurons continues to enrich our understanding of this neurophysiology.

More than eight years' hands-on experience with the novel long-acting parenteral testosterone undecanoate

Testosterone (T) as a compound for treatment of T deficiency has been available for almost 70 years, but the pharmaceutical formulations have been less than ideal. Traditionally, injectable T esters have been used for treatment, but they generate supranormal T levels shortly after the 2-3 weekly injection interval. T levels then decline very rapidly, becoming subnormal during the days preceding the next injection. The rapid fluctuations in plasma T are subjectively experienced as disagreeable. T undecanoate (TU) is a new injectable T preparation with a considerably better pharmacokinetic profile. After two initial injections separated by a 6-week interval, the following intervals between two injections are generally 12 weeks, eventually amounting to a total of four injections per year. Plasma T levels with this preparation are nearly always in the range of normal men, as are its metabolic products estradiol and dihydrotestosterone (DHT). It reverses the effects of hypogonadism on bone and muscle and metabolic parameters, and on sex functions. It is suitable for male contraception. Its safety profile is excellent because of the continuous normalcy of plasma T levels. No polycythemia has been observed and no adverse effects on lipid profiles. Prostate safety parameters are well within reference limits. TU is a valuable treatment option of androgen deficiency.

Effects of testosterone on erectile function: implications for the therapy of erectile dysfunction

Sexual potency declines with age, as does the efficiency of erection. Many studies show that different patterns of erectile dysfunction (ED), varying from occasional inability to obtain a full erection, impairment throughout intercourse and total absence of erectile response, might not be triggered by psychological factors only. Recent research indicates that ED relies on organic causes, and has challenged the development of new therapies. One therapeutic approach in patients who have testosterone deficiency is based on androgen therapy. Thus, we reviewed data on testosterone-induced effects relative to erectile function, summarizing the results from studies reported in 1991-2006 on testosterone therapy in patients with ED and hypogonadism, with a special focus on men not responding to phosphodiesterase-5 (PDE-5) inhibitors. We searched several computerized databases parallel with printed bibliographic references. Many studies have established animal models, which confirm that testosterone is important in modulating the central and peripheral regulation of ED. Testosterone deprivation has a strong negative impact on the structure of penile tissues and erectile nerves, which can be prevented by androgen administration. Combined therapy regimens with PDE-5 inhibitors and testosterone might improve ED in patients with hypogonadism of different causes. Thus, androgen treatment in hypogonadic patients, including those unresponsive to PDE-5 inhibitors, often results in an improvement of ED. Testosterone therapy is safe and convenient, while rapidly correcting low testosterone levels.

ORIGINAL RESEARCH—ENDOCRINOLOGY: Improvement of Sexual Function in Men with Late-Onset Hypogonadism Treated with Testosterone Only

AIM

Late-onset hypogonadism is associated with relatively mild testosterone deficiencies. This study investigated the effects of restoring testosterone levels to normal in men with complaints of low sexual desire and erectile dysfunction.

MAIN OUTCOME MEASURES

Sexual function was assessed with the International Index of Erectile Function (IIEF) at baseline and after 24 weeks of testosterone administration.

METHODS

Twenty-two hypogonadal men (mean age 58 years) with erectile dysfunction were studied. Fifteen patients had serum testosterone below 6.9 nmol/L, and seven between 7.2 and 11.7 nmol/L (reference values in our laboratory >/=12.0 nmol/L); there were considerable comorbidities. The duration of sexual complaints was on average 3.8 years. Patients received intramuscular long-acting testosterone undecanoate.

RESULTS

In all patients, serum testosterone levels were restored to normal within 6-8 weeks. Twelve patients reported a significant improvement in the sexual desire domain (from 4.5 to 8.4) and experienced an improvement in the erectile function domain (from 12 to 25 [Questions 1-5 plus 15)], following treatment with this long-acting testosterone; in 9 of 12 patients, this occurred only after at least 12-24 weeks. The remaining 10 patients reported an improvement of sexual desire (from 4.5 to 7.5), but no significant improvement in the erectile function domain (from 12 to 14). No changes in serum prostate-specific antigen or prostate volume were noticed while receiving this long-acting testosterone preparation.

CONCLUSION

Restoring testosterone levels to normal in men with proven subnormal testosterone levels improves libido in most subjects, and erectile function in more than 50% of these men. It may take 12-24 weeks before the effects of testosterone become manifest.

Testosterone and erectile function: from basic research to a new clinical paradigm for managing men with androgen insufficiency and erectile dysfunction

OBJECTIVES

Androgens are essential for the development and growth of the penis, and they regulate erectile physiology by multiple mechanisms. Our goal is to provide a concise overview of the basic research and how this knowledge can be translated into a new clinical paradigm for patient management. In addition, this new paradigm may serve as a basis for stimulating constructive debate regarding the use of testosterone in men, and to promote new, innovative basic and clinical research to further understand the underlying mechanisms of androgen action in restoring erectile physiology.

METHODS

A literature review was performed utilizing the US National Library of Medicine's PubMed database.

RESULTS

On the basis of evidence derived from laboratory animal studies and clinical data, we postulate that androgen insufficiency disrupts cellular-signaling pathways and produces pathologic alterations in penile tissues, leading to erectile dysfunction. In this review, we discuss androgen-dependent cellular, molecular, and physiologic mechanisms modulating erectile function in the animal model, and the implication of this knowledge in testosterone use in the clinical setting to treat erectile dysfunction. The new clinical paradigm incorporates many of the consensed points of view discussed in traditional consensed algorithms exclusively designed for men with androgen insufficiency. There are, however, novel and innovative differences with this new clinical paradigm. This paradigm represents a fresh effort to provide mandatory and optional management strategies for men with both androgen insufficiency and erectile dysfunction.

CONCLUSIONS

The new clinical paradigm is evidence-based and represents one of the first attempts to address a logical management plan for men with concomitant hormonal and sexual health concerns.

Gene therapy and erectile dysfunction: the current status

Current available treatment options for erectile dysfunction (ED) are effective but not without failure and/or side effects. Although the development of phosphodiesterase type 5 (PDE5) inhibitors (i.e. sildenafil, tadalafil and vardenafil) has revolutionized the treatment of ED, these oral medications require on-demand access and are not as effective in treating ED related to diabetic, post-prostatectomy and severe veno-occlusive disease states. Improvement in the treatment of ED is dependent on understanding the regulation of human corporal smooth muscle tone and on the identification of relevant molecular targets. Future ED therapies might consider the application of molecular technologies such as gene therapy. As a potential therapeutic tool, gene therapy might provide an effective and specific means for altering intracavernous pressure "on demand" without affecting resting penile function. However, the safety of gene therapy remains a major hurdle to overcome before being accepted as a mainstream treatment for ED. Gene therapy aims to cure the underlying conditions in ED, including fibrosis. Furthermore, gene therapy might help prolong the efficacy of the PDE5 inhibitors by improving penile nitric oxide bioactivity. It is feasible to apply gene therapy to the penis because of its location and accessibility, low penile circulatory flow in the flaccid state and the presence of endothelial lined (lacunar) spaces. This review provides a brief insight of the current role of gene therapy in the management of ED.

Different hemodynamic responses by color Doppler ultrasonography studies between sildenafil non-responders and responders

AIM

To determine if there are different penile hemodynamic patterns between sildenafil non-responders and responders by using color Doppler ultrasonography.

METHODS

A total of 69 erectile dysfunction (ED) patients aged 22-79 years were enrolled into the present study. Thirty-eight (55.1%) men with ED who did not respond to four attempts of treatment with 100 mg sildenafil after re-education were classified as sildenafil non-responders. A combination of three vasodilator drugs, 1.25 mg papaverine, 0.4 mg phentolamine and 5 mg prostaglandin E1, was given by intracavernous injection before penile Doppler ultrasonography was carried out. The erectile response to intracavernous injection and vascular parameters including peak systolic velocity (PSV), resistance index (RI), end diastolic velocity (EDV) and cavernosa artery diameter (CD) were measured and the results between sildenafil non-responders and responders were compared.

RESULTS

No statistical difference in vascular parameters measured by Doppler ultrasonography studies between non-responders and responders was noted. Sildenafil non-responders had a poorer penile rigidity response to intracavernous injection than responders (P < 0.05). Among patients with adequate PSV (>or=30 cm/s) and abnormal EDV (> 5 cm/s), individuals in the non-responder group had fewer positive responses to intracavernous vasodilator injection than in the responder group (35.3% vs. 72.2%, P < 0.05). Advanced age and comorbidity with diabetes mellitus were significantly associated with sildenafil non-response (P < 0.05).

CONCLUSION

Sildenafil non-responders were characterized by a poorer penile rigidity response to intracavernous injection and had an associated impaired veno-occlusive mechanism. Advanced age and comorbidity with diabetes mellitus were two common factors associated with non-response.

Treatment of sexual dysfunction of hypogonadal patients with long-acting testosterone undecanoate (Nebido®)

Recently, testosterone undecanoate (TU), a new parenteral testosterone (T) preparation has been introduced. Two of its distinctive features are (a) its prolonged action: after two initial loading injections 6 weeks apart, usually only one injection every 12 weeks is needed (b) over the full interval between two injections, plasma T levels are in the physiological range. New research presents convincing evidence that T has profound effects on tissues of the penis involved in the mechanism of erection and that testosterone deficiency impairs the anatomical and physiological substrate of erectile capacity, which is, at least, in part reversible upon androgen therapy. Our studies with TU demonstrated that venous leakage could be corrected with T treatment in a number of patients. We further could show that sexual functions, in a substantial number of elderly men, can be restored with treatment with T only. So, these results argue for determination of T levels in elderly men with sexual problems. If the levels are subnormal, T treatment is warranted.

Testosterone decreases adiponectin levels in female to male transsexuals

AIM

To evaluate the effect of testosterone (T) on adiponectin serum levels in transsexual female patients.

METHODS

We measured adiponectin, leptin, luteinizing hormone and follicle stimulating hormone, T, estradiol, lipid profile, biochemical parameters and body composition in 16 transsexual female patients at baseline and after 6 months of T treatment (100 mg Testoviron Depot /10 days, i.m.).

RESULTS

Adiponectin levels were 16.9 +/- 7.3 mg/mL at baseline and 13.5 +/- 7.4 mg/mL at month 6 of T treatment (P < 0.05). Leptin and high-density lipoprotein cholesterol decreased significantly, whereas body mass index, waist circumference and lean body mass increased significantly after 6 months of T treatment. No changes in insulin or Homeostasis Model Assessment were detected.

CONCLUSION

T can significantly reduce adiponectin serum levels in transsexual female patients.