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

Androgens modulate endothelial function and endothelial progenitor cells in erectile physiology

The incidence of erectile dysfunction (ED) increases with age and cardiovascular disease risk factors, such as hypertension, hyperlipidemia, insulin resistance, obesity, and diabetes. These risk factors are thought to contribute to endothelial dysfunction and atherosclerosis, thus contributing to the pathophysiology of ED. The role of the endothelium in regulating erectile physiology is well established. However, the role of androgens in modulating endothelial function and endothelial repair mechanisms subsequent to vascular injury in erectile tissue remains a subject of intensive research. The clinical and preclinical evidence discussed in this review suggests that androgens regulate endothelial function and also play an important role in the development and maturation of endothelial progenitor cells (EPCs), which are thought to play a critical role in repair of endothelial injury in vascular beds. In this review, we discuss the data available on the effects of androgens on endothelial function and EPCs in the repair of vascular injury. Indeed, more research is needed to fully understand the molecular and cellular basis of androgen action in regulating the development, differentiation, maturation, migration, and homing of EPCs to the site of injury. A better understanding of these processes will be critical to the development of new therapeutic approaches to the treatment of vascular ED.

Do testosterone declines during the transition to marriage and fatherhood relate to men's sexual behavior? Evidence from the Philippines

Testosterone (T) is thought to help facilitate trade-offs between mating and parenting in humans. Across diverse cultural settings married men and fathers have lower T than other men and couples' sexual activity often declines during the first years of marriage and after having children. It is unknown whether these behavioral and hormonal changes are related. Here we use longitudinal data from a large study in the Philippines (n=433) to test this model. We show that among unmarried non-fathers at baseline (n=153; age: 21.5 ± 0.3 years) who became newly married new fathers by follow-up (4.5 years later), those who experienced less pronounced longitudinal declines in T reported more frequent intercourse with their partners at follow-up (p<0.01) compared to men with larger declines in T. Controlling for duration of marriage, findings were similar for men transitioning from unmarried to married (without children) (p<0.05). Men who remained unmarried and childless throughout the study period did not show similar T-sexual activity outcomes. Among newly married new fathers, subjects who had frequent intercourse both before and after the transition to married fatherhood had more modest declines in T compared to peers who had less frequent sex (p<0.001). Our findings are generally consistent with theoretical expectations and cross-species empirical observations regarding the role of T in male life history trade-offs, particularly in species with bi-parental care, and add to evidence that T and sexual activity have bidirectional relationships in human males.

Energy restriction ameliorates metabolic syndrome-induced cavernous tissue structural modifications in aged rats

High-fat (HF) diet regular intake along life highly contributes to vascular dysfunction and to an increment in prevalence of metabolic syndrome (MetS) and erectile dysfunction (ED), a surrogate symptom of occult vascular disease, in the elderly. However, little is known about the effects of energy restriction (ER) alone/or after an HF-feeding period. We show here that in male Sprague-Dawley rats, 16 months of HF-diet consumption led to an increase in body adiposity, blood pressure, lipidemia, C-reactive protein, and insulin resistance and to hypoadiponectinemia, conditions that cluster in MetS. In addition, this treatment strongly favored collagen deposition in cavernous tissue and myocardium. Conversely, for the same time period, the ingestion of 75 % of ad libitum energy intake by controls (ER) extensively counteracted these outcomes. The impact of 6-month ER after 10-month HF period was also analyzed, and despite the decrease in body weight, adiposity, blood pressure, lipidemia, and C-reactive protein and improvement of insulin sensitivity, no differences were observed either in adiponectin blood levels or in retroperitoneal fat pad mass. Moreover, this treatment led to a reduction in cavernous tissue collagen deposition, but not in the myocardium, and evidenced differential mobilization of adipose tissue accretions. The data show the ability of HF diet to cause MetS and produce unwanted effects on myocardium and corpora vascular structure. They also indicate that these consequences are preventable upon ER diet starting early, but not later, in life.

A systematic review of the association between erectile dysfunction and cardiovascular disease

CONTEXT

Erectile dysfunction (ED) is considered a vascular impairment that shares many risk factors with cardiovascular disease (CVD). A correlation between ED and CVD has been hypothesized, and ED has been proposed as an early marker of symptomatic CVD.

OBJECTIVE

To analyze the relationship between ED and CVD, evaluating the pathophysiologic links between these conditions, and to identify which patients would benefit from cardiologic assessment when presenting with ED.

EVIDENCE ACQUISITION

A systematic literature review searching Medline, Embase, and Web of Science databases was performed. The search strategy included the terms erectile dysfunction, cardiovascular disease, coronary artery disease, risk factors, pathophysiology, atherosclerosis, low androgen levels, inflammation, screening, and phosphodiesterase type 5 inhibitors alone or in combination. We limited our search to studies published between January 2005 and May 2013.

EVIDENCE SYNTHESIS

Several studies reported an association between ED and CVD. The link between these conditions might reside in the interaction between androgens, chronic inflammation, and cardiovascular risk factors that determines endothelial dysfunction and atherosclerosis, resulting in disorders of penile and coronary circulation. Because penile artery size is smaller compared with coronary arteries, the same level of endothelial dysfunction causes a more significant reduction of blood flow in erectile tissues compared with that in coronary circulation. Thus ED could be an indicator of systemic endothelial dysfunction. From a clinical standpoint, because ED may precede CVD, it can be used as an early marker to identify men at higher risk of CVD events. ED patients at high risk of CVD should undergo detailed cardiologic assessment and receive intensive treatment of risk factors.

CONCLUSIONS

ED and CVD should be regarded as two different manifestations of the same systemic disorder. ED usually precedes CVD onset, and it might be considered an early marker of symptomatic CVD.

Long-term oral administration of 5α-reductase inhibitor attenuates erectile function by inhibiting autophagy and promoting apoptosis of smooth muscle cells in corpus cavernosum of aged rats

OBJECTIVE

To investigate the effects and mechanisms of long-term treatment of 5α-reductase inhibitors (5ARIs) on erectile organ structure and function in aged rats.

MATERIALS AND METHODS

Thirty 16-month-old male rats were assigned to 2 groups: untreated or treated with 5ARIs. After 16 weeks, the erectile function was measured after electrical stimulation of the cavernous nerve. The weights and histopathologic features of the corpus cavernosum were examined. The levels of autophagy, apoptosis, and protein expression were also recorded.

RESULTS

In the 5ARI-treatment group, the plasma and intraprostatic dihydrotestosterone concentration was lowered by 52.1% and 57.3%, respectively, and the weight of the corpus cavernosum and prostate had decreased by 22.4% and 35.6%, respectively. The in vivo erectile response to electrical stimulation of the cavernous nerve had decreased significantly in the 5ARI-treatment group (P <.001). Masson's staining, immunohistochemistry, and Western blot all demonstrated decreased smooth muscle and increased collagen deposition and decreased endothelial nitric oxide synthase and LC3-II protein expression in the corpus cavernosum of the 5ARI-treatment group. Using transmission electron microscopy and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling, decreased autophagy, aggravated ultrastructural injury of mitochondria, and increased apoptosis were observed in the cavernous smooth muscle cells from the rats in the 5ARI-treatment group.

CONCLUSION

Long-term 5ARI treatment did attenuate the erectile function of aged rats. The mechanisms might have been the decreased rate of autophagy and an increased rate of apoptosis in the cavernous smooth muscle cells, suggesting a new role for androgen in maintaining the structural and functional integrity of the erectile organ. Additional studies are necessary to demonstrate the mechanisms of dihydrotestosterone in regulating the autophagy and apoptosis of the cavernous smooth muscle cells.

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.

Androgen depletion in humans leads to cavernous tissue reorganization and upregulation of Sirt1-eNOS axis

Aging and physiological androgen decay leads to structural changes in corpus cavernosum (CC) that associate with erectile function impairment. There is evidence that such changes relate to nitric oxide (NO) bioavailability, an endothelial compound produced by the action of endothelial NO synthase (eNOS), and is regulated by sirtuin-1 (Sirt1), a NAD(+)-dependent protein deacetylase. Taking into account the reduced NO synthesis observed in aging and erectile dysfunction, we aimed to characterize human CC of androgen-deprived, young, and aged individuals postulating that androgen deprivation induces modifications similar to those observed in aging. Human penile fragments were collected from young individuals submitted to male-to-female sex reassignment procedure, who undergone an androgen deprivation chemical regimen, from young organ donors and from aged patients submitted to penile deviation surgery. They were processed for histomorphometric analysis of smooth muscle (SM) and connective tissues (CT), and dual-immunofluorescence of alpha-actin/vWf or Sirt1, and endothelin-1/eNOS. Estrogen receptors were analyzed by immunohistochemistry and semiquantification of Sirt1, eNOS, and phospho-Akt was assayed by Western blotting. Androgen withdrawal, similarly to aging, leads to a noteworthy reduction of SM-to-CT ratio in CC. However, in contrast to young and aged, a significant increase in penile Sirt1 expression accompanied by an increase in total eNOS expression was observed in androgen-depleted individuals. No changes were evidenced in phospho-Akt system and estrogen receptors were undetectable. These findings indicate that Sirt1 regulates the expression of eNOS in human CC employing mechanisms influenced by androgen depletion.

Low testosterone levels induce apoptosis via active 3-caspase dependent signaling in the bladder wall of male rats

OBJECTIVE

The bladder can be considered a target organ for testosterone action, and low testosterone levels possibly cause damage to bladder cells. We set out to study whether hypoandrogenism influences bladder wall cell damage in castrated and senile male rats.

METHODS

Thirty male Wistar rats were divided into three groups of 10 animals each: group I (3 months old), sham animals; group II (27 months old), senile animals; group III (3 months old), subjected to bilateral orchiectomy, and sacrificed 8 weeks after the procedure. Bladders were excised, weighed and sent for analysis. Stereological assays on collagen fibers and immunohistochemical analysis with active 3-caspase were performed on bladder cells.

RESULTS

Bladder weights were greater in the senile group than in the others. Stereological collagen fiber analysis demonstrated higher density in group III than in groups I and II (p < 0.05). The absolute density was 4.15 mm(3) in group I, 22.3 mm(3) in group II and 19.3 mm(3) in group III. Semiquantitative active 3-caspase analysis showed greater percentages in the senile group II than in groups I and III.

CONCLUSIONS

We can state that low plasma testosterone levels are related to higher collagen fiber density and active 3-caspase percentages in the bladder walls of orchiectomized and senile rats, respectively.

Synergetic effect of testosterone and phophodiesterase-5 inhibitors in hypogonadal men with erectile dysfunction: A systematic review

Testosterone deficiency seems to impair the clinical response to phophodiesterase-5 (PDE-5) inhibitors in patients with erectile dysfunction (ED). In hypogonadal men, testosterone repletion was associated with enhanced sexual function in patients who failed initial treatment with sildenafil or tadalafil. We conducted a systematic review of studies that evaluated combination therapy of testosterone and PDE-5 inhibitors in patients with ED and low, low-normal testosterone levels who failed monotherapy. The studies we examine are heterogeneous with several methodological drawbacks and that, overall, the addition of testosterone to PDE-5 inhibitors might benefit patients with ED associated with testosterone <300 ng/dL (10.4 nmol/L) who failed monotherapy. Further studies, with a randomized placebo-controlled and double blind design, are needed to describe the appropriate target patient group, testosterone cut-off and to define the optimal dose and duration of combination therapy.

Testosterone is associated with erectile dysfunction: a cross-sectional study in Chinese men

BACKGROUND

Testosterone is essential for the regulation of erectile physiology, but the relationship between low testosterone and erectile dysfunction (ED) has not been firmly established.

PURPOSE

To examine the association between serum total, free and bio-available testosterone and ED in a population-based sample.

METHODS

A consecutive series of 1776 men aged 20-77 participated in the routine physical examination from September 2009 to December 2009 in Guangxi, China. ED was assessed using the five-item International Index of Erectile Function (IIEF-5) questionnaire. Total testosterone (TT), sex hormone binding globulin (SHBG) and other biochemical profiles were measured. Free testosterone (FT) and bio-available testosterone (BT) were calculated based on Vermeulen's formula. Data were collected with regard to smoking, alcoholic drinking, physical activity and metabolic syndrome.

RESULTS

The prevalence of ED (IIEF-5<22) was 47.6%. Men with ED were significantly older, and more prone to smoke cigarettes (≥20 cigarettes/day) or drink alcohol (≥3 drinks/week), and more likely to have elevated blood pressure (P = 0.036) or hyperglycemia (P<0.001) compared with those without ED. The significant increase in SHBG with age was parallel to its increase with increasing severity of ED (P<0.001). The obscure increase in TT across the ED status was detected without significance (P = 0.418), but TT was positively associated with ED after adjustment for age [odds ratio (OR)  = 1.02, 95% CI (confidence internal): 1.00-1.04]. FT and BT were inversely associated with ED (OR = 0.14, 95%CI: 0.06-0.33; OR = 0.92 (95%CI: 0.89-0.96, respectively) in the univariate analysis, and this inverse association appeared to be independent of smoking status, alcoholic drinking, physical activity, hyper-triglyceridemia and hyperglycemia.

CONCLUSIONS

FT and BT are inversely related to worsening ED, whereas the positive association between TT and ED is most likely due to the increase in SHBG.

Androgen deprivation induces bladder histological abnormalities and dysfunction via TGF-β in orchiectomized mature rats

Symptomatic late-onset hypogonadism, one of the most common elder diseases, is defined as a syndrome associated with a deficiency in serum testosterone. Recent studies have indicated that androgen deficiency in men is also associated with lower urinary tract symptoms and bladder dysfunction. To determine the pathologic consequences of androgen deprivation in bladder histology and function, we addressed the underlying mechanism. Male rats were divided into 4 groups: emasculated rats (EMR), emasculated rats treated with testosterone, emasculated rats treated with anti- transforming growth factor-β (TGF-β) neutralizing antibody, and sham surgery rats. TGF-β is a common profibrotic factor that mediates the pathologic process of fibrosis in multiple organs. Two months later, urodynamic evaluations were employed to determine the bladder function in vivo. And then rats were sacrificed, and the bladder tissues were collected. Histological studies were employed to determine the degree of bladder fibrosis. Real time PCR was used to evaluate the mRNA level of pro-collagen I, a fibrotic marker. We demonstrate here that androgen deficiency induces bladder fibrosis and decreases the bladder maximal volume and compliance. Androgen replacement treatment completely prevented the histological and functional abnormalities induced by androgen deficiency. Subsequently, we identified that androgen deprivation induced the induction of TGF-β mRNA level. Importantly, treatment with anti-TGF-β antibody abolished androgen deprivation-induced bladder fibrosis and dysfunction. Our study reveals an essential role of TGF-β in the pathogenesis of androgen deprivation-induced bladder fibrosis and dysfunction and offers a potential target for prevention and treatment of bladder dysfunction associated with androgen deficiency.

Impact of androgen deprivation therapy on sexual function

Many patients with prostate cancer for whom androgen deprivation therapy (ADT) is indicated are young and desire to remain sexually active. In such patients, the side effects of androgen therapy on sexual function can be a source of serious reduction in overall quality of life. Providing the appropriate treatment options in this patient population is therefore essential. Nevertheless, treating such patients is challenging and an understanding of the underlying mechanisms of sexual physiology and pathophysiology is crucial to optimal patient care. In this paper, we reviewed what was known regarding the effects of ADT on sexual function in animal models and we also provided a detailed review on the effects of ADT on sexual health in humans and its treatment.

Testosterone, endothelial health, and erectile function

Experimental and clinical studies have reported that testosterone has a critical role in the maintenance of homeostatic and morphologic corpus cavernosum components, essential for normal erectile physiology. Although the exact mechanisms mediated by testosterone in erectile function are still under investigation, recent research has suggested an important role in the regulation of endothelial cell (EC) biological functions. Besides stimulating the production of EC mediators, testosterone is also thought to promote the vasculogenic reendothelialization process, mediated by bone marrow-derived endothelial progenitor cells. Additionally, testosterone seems to modulate other erectile tissue components, including trabecular smooth muscle cells, nerve fibers, and tunica albuginea structure, all essential for the erectile process. This paper summarizes current data regarding testosterone-induced cellular and molecular mechanisms that regulate penile tissue components, focusing particularly on the role of testosterone in endothelial health and erectile function.

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.

The association of testosterone, sleep, and sexual function in men and women

Testosterone has been the focus of several investigations and review studies in males, but few have addressed its effects on sleep and sexual function, despite evidence of its androgenic effects on circadian activity in both sexes. Studies have been conducted to understand how sleeping increases (and how waking decreases) testosterone levels and how this rhythm can be related to sexual function. This review addresses the inter-relationships among testosterone, sexual function and sleep, including sleep-disordered breathing in both sexes, specifically its effects related to sleep deprivation. In addition, hormonal changes in testosterone that occur in the gonadal and adrenal axis with obstructive sleep apnea and other conditions of chronic sleep deprivation, and which consequently affect sexual life, have also been explored. Nevertheless, hormone-associated sleep disruptions occur across a lifetime, particularly in women. The association between endogenous testosterone and sex, sleep and sleep disturbances is discussed, including the results of clinical trials as well as animal model studies. Evidence of possible pathophysiological mechanisms underlying this relationship is also described. Unraveling the associations of sex steroid hormone concentrations with sleep and sexual function may have clinical implications, as sleep loss reduces testosterone levels in males, and low sex steroid hormone concentrations have been associated with sexual dysfunction.

Symptomatic therapy in multiple sclerosis

Multiple sclerosis is the most common disabling neurological disease of young adults. The ability to impact the quality of life of patients with multiple sclerosis should not only incorporate therapies that are disease modifying, but should also include a course of action for the global multidisciplinary management focused on quality of life and functional capabilities.

Hypogonadal men nonresponders to the PDE5 inhibitor tadalafil benefit from normalization of testosterone levels with a 1% hydroalcoholic testosterone gel in the treatment of erectile dysfunction (TADTEST study)

INTRODUCTION

Addition of testosterone (T) may improve the action of phosphodiesterase type 5 inhibitors (PDE5-Is) in patients with erectile dysfunction not responding to PDE5-Is with low or low-normal T levels.

AIMS

To confirm this add-on effect of T in men optimally treated with PDE5-Is and to specify the baseline T levels at which such an effect becomes significant.

METHODS

A multicenter, multinational, double-blind, placebo-controlled study of 173 men, 45-80 years, nonresponders to treatment with different PDE5-Is, with baseline total T levels ≤ 4 ng/mL or bioavailable T ≤ 1 ng/mL. Men were first treated with tadalafil 10 mg once a day (OAD) for 4 weeks; if not successful, they were randomized in a double-blind, placebo-controlled design to receive placebo or a 1% hydroalcoholic T gel (50 mg/5 g gel), to be increased to 10 mg T if results were clinically unsatisfactory. Main Outcomes Measures.  Mean change from baseline in the Erectile Function Domain Score of the International Index of Erectile Function and rate of successful intercourses (Sexual Encounter Profile 3 question).

RESULTS

Erectile function progressively improved over a period of at least 12 weeks in both the placebo and T treatment groups. In the overall population with a mean baseline T level of 3.37 ± 1.48 ng/mL, no additional effect of T administration to men optimally treated with PDE5-Is was encountered. The differences between the T and placebo groups were significant for both criteria only in the men with baseline T ≤ 3 ng/mL.

CONCLUSIONS

The maximal beneficial effects of OAD dosing with 10 mg tadalafil may occur only after as many as 12 weeks. Furthermore, addition of T to this PDE5-I regimen is beneficial, but only in hypogonadal men with baseline T levels ≤ 3 ng/mL.

Reversion of penile fibrosis: Current information and a new horizon

Ageing has a detrimental effect on cavernous tissue and the tunica albuginea of the penis. Furthermore, atherosclerosis of the penile vessels that occurs with ageing causes a decrease in penile oxygen tension. A reduction in smooth muscle cells (SMCs) was shown in relation to diminution of oxygen tension. Chronic ischaemia is therefore not only associated with fibrosis but also with nitric oxide-cyclic guanosine monophosphate reduction. The sensitivity of the α-adrenoceptors on the SMCs increases with ageing. The decrease in penile elasticity and compliance are explained by the changes in the ratio of penile collagen that occur with ageing. Contradictory to the view that testosterone is only necessary for sexual desire, numerous recent studies showed that androgen deprivation produces penile tissue atrophy, alterations in dorsal nerve structure, alterations in endothelial morphology, reduction in trabecular SM content, increase in deposition of extracellular matrix and accumulation of fat-containing cells (adipocytes) in the subtunical region of corpus cavernosum. The aim of the current review is to shed some light on the underlying aetiology of corporal fibrosis especially ageing, cavernous nerve damage, androgen deprivation and tunical fibrosis. Ultimately I will address the proposed prevention of erectile dysfunction associated with penile fibrosis.

Testosterone Replacement Therapy in Males With Erectile Dysfunction

Erectile dysfunction (ED) is defined as the inability to achieve or maintain an erection sufficient for satisfactory sexual performance. Endogenous testosterone is critical for normal libido; however, studies have also demonstrated a potentially important role with respect to the erectile process. The prevalence of testosterone deficiency ranges from 1.7% to 35% in patients with ED, and age is a common factor linking ED and testosterone deficiency. By 2025, global estimates are that there will be 356 million men >65 years. Age-associated testosterone deficiency is characterized by symptoms such as ED, and low serum testosterone. Randomized, placebo controlled studies have established the utility of testosterone replacement therapy (TRT) for the restoration of serum testosterone levels to the normal range in hypogonadal males; however, well designed studies are limited with respect to specific evaluation of the role of TRT as monotherapy in improving erectile function. In addition, recent literature suggests a possible role for TRT in combination with phosphodiesterase-5 (PDE-5) inhibitors for men with ED. The following review describes the potential roles of testosterone in erectile physiology, examines the relationship between testosterone deficiency and ED, and reviews published literature evaluating the use of TRT in hypogonadal males with a diagnosis of ED.

Androgen replacement therapy contributes to improving lower urinary tract symptoms in patients with hypogonadism and benign prostate hypertrophy: a randomised controlled study

PURPOSE

We performed a randomised controlled study regarding the effects of androgen replacement therapy (ART) on lower urinary tract symptoms (LUTS) in hypogonadal men with benign prostate hypertrophy (BPH).

METHODS

Fifty-two patients with hypogonadism and BPH were randomly assigned to receive testosterone (ART group) as 250 mg of testosterone enanthate every 4 weeks or to the untreated control group. We compared International Prostate Symptom Score (IPSS), uroflowmetry data, post-voiding residual volume (PVR) and systemic muscle volume at baseline and 12 months after treatment.

RESULTS

Forty-six patients (ART group, n=23; control, n=23) were included in the analysis. At the 12-month visit, IPSS showed a significant decrease compared with baseline in the ART group (15.7 +/- 8.7 vs. 12.5 +/- 9.5; p<0.05). No significant changes were observed in the control group. The ART group also showed improvement in maximum flow rate and voided volume (p<0.05), whereas no significant improvements were observed in the controls. PVR showed no significant changes in either group. In addition, the ART group showed significant enhancement of mean muscle volume (p<0.05), whereas no significant changes were seen in the controls.

CONCLUSION

ART improved LUTS in hypogonadal men with mild BPH.

Update on corpus cavernosum smooth muscle contractile pathways in erectile function: a role for testosterone?

INTRODUCTION

Normal erectile function (EF) involves a coordinated relaxation of the arteries that supply the penis and the corpus cavernosum smooth muscle (CCSM), resulting in expansion of the sinusoids and increased intracavernous pressure. But the CCSM spends the majority of its time in the contracted state which is mediated by norepinephrine released from nerve endings and other vasoconstrictors like endothelins released from the endothelium. These agents cause smooth muscle myosin (SMM) phosphorylation by elevating intracellular calcium. When calcium returns to basal levels, the calcium sensitivity increases and prevents myosin dephosphorylation, which involves the RhoA/Rho-kinase (ROK) mechanism, thus maintaining force. Although mounting evidences demonstrate that androgens have a major influence on EF that is not just centrally mediated, this notion remains quite controversial.

AIM

To summarize the current knowledge on CCSM contractile pathways, the role they play in modulating EF, and the influence of androgens.

METHODS

The article reviews the literature and contains some previously unpublished data on CCSM contraction signaling including the role that androgens are known to play in modulating these pathways.

MAIN OUTCOME MEASURES

Data from peer-reviewed publications and previously unpublished observations.

RESULTS

In addition to downregulation of many pro-erectile molecular mechanisms, decreased testosterone (T) levels upregulate CCSM contractility, including hyperresponsiveness to α-adrenergic agonists, increased SMM phosphorylation, alteration of SMM isoform composition, activation of RhoA/ROK signaling and modulation of sphingosine-1-phosphate regulation of CCSM tone.

CONCLUSIONS

Decreased T levels upregulate CCSM contractile signaling. Meanwhile, it downregulates CCSM relaxation pathways synergizing to produce erectile dysfunction (ED). Although some urologists and researchers are still skeptical of the influence of androgens on penile erection, understanding these molecular control mechanisms as well as the influence that androgens have on these pathways should provide new evidence supporting the roles of androgens in EF and enhance the discovery of novel targets for drug development to treat ED.

Quality of life, self-esteem, fatigue, and sexual function in young men after cancer: a controlled cross-sectional study

BACKGROUND

Androgen deficiency is increasingly recognized in young male cancer survivors; however, its impact on quality of life (QOL) is not established. The authors investigated the relationship between androgen levels, QOL, self-esteem, fatigue, and sexual function in young male cancer survivors compared with control subjects.

METHODS

A cross-sectional, observational study of 176 male cancer survivors and 213 male controls aged 25 to 45 years was performed. Subjects completed 3 QOL scales (Medical Outcomes Study 36-Item Short-Form Health Survey version 2, the 12-item General Health Questionnaire [GHQ-12], and Aging Male Scale), and measures of self-esteem (Rosenberg Self-Esteem Scale), fatigue (Functional Assessment of Chronic Illness Therapy-Fatigue), and sexual function (Derogatis Interview for Sexual Functioning-II Self-Report-Male).

RESULTS

Cancer survivors had lower scores for all components of the Short-Form Health Survey, Aging Male Scale, and Functional Assessment of Chronic Illness Therapy-Fatigue, and for 4 of 5 subsections of the Derogatis Interview for Sexual Functioning than controls. The majority of these differences remained after adjusting by linear regression analysis. Levels of psychiatric disorder or self-esteem did not differ between the 2 groups. In cancer survivors, those with androgen deficiency (serum testosterone < or = 10 nmol/L) had lower scores than those without for all components of the Short-Form Health Survey, the General Health Questionnaire, Functional Assessment of Chronic Illness Therapy-Fatigue, and the Derogatis Interview for Sexual Functioning. Serum testosterone only weakly correlated with health measures.

CONCLUSIONS

Young male cancer survivors self-report a marked impairment in QOL, energy levels, and quality of sexual functioning, and this was exacerbated in those with androgen deficiency. However, psychological distress was not elevated, self-esteem was normal, and sexual relationships were not impaired. The relationship with testosterone is complex, and appears dependent on a threshold level rather than direct correlation. Interventional trials are needed to determine whether testosterone replacement would improve QOL in young male cancer survivors.

Androgens and male aging: Current evidence of safety and efficacy

Many signs of aging, such as sexual dysfunction, visceral obesity, impaired bone and muscle strength, bear a close resemblance to features of hypogonadism in younger men. The statistical decline of serum testosterone in aging men is solidly documented. It has been presumed that the above features of aging are related to the concurrent decline of androgens, and that correction of the lower-than-normal circulating levels of testosterone will lead to improvement of symptoms of aging. But in essence, the pivotal question whether the age-related decline of testosterone must be viewed as hypogonadism, in the best case reversed by testosterone treatment, has not been definitively resolved. Studies in elderly men with lower-than-normal testosterone report improvement of features of the metabolic syndrome, bone mineral density, of mood and of sexual functioning. But as yet there is no definitive proof of the beneficial effects of restoring testosterone levels to normal in elderly men on clinical parameters. Few of these studies meet as yet rigorous standards of scientific enquiry: double-blind, placebo-controlled design of the study. The above applies also to the assessment of safety of testosterone administration to elderly men. There is so far no convincing evidence that testosterone is a main factor in the development of prostate cancer in elderly men and guidelines for monitoring the development of prostate disease have been developed. It is of note that there are presently no long-term safety data with regard to the prostate. Polycythemia is another potential complication of testosterone treatment. It is dose dependent and can be managed with dose adjustment.

Sexual dysfunction in the older man

Age is strongly associated with risk of sexual dysfunction in both men and women. For many years it was assumed that such a loss of sexuality was natural and inevitable, and therefore little attention was given to sexual behaviour and treatment in this population. However, more recent data have suggested that sexuality remains important into later life for many individuals. Although appreciation of sexuality persists, a decline in sexual activity is typical with advancing age, which is in part attributable to both general health problems and specific sexual dysfunctions, both becoming more prevalent with ageing. The principle sexual health issues in older men include erectile dysfunction and late onset hypogonadism. Although premature ejaculation is prevalent in older men, the bother from this disorder is generally lower in older men. This manuscript consists of a review of the contemporary peer-reviewed literature and attempts to provide insights for the physician treating the geriatric population. We discuss sexual behaviour at older age, and address erectile and androgen biology in older men and the prevalence and aetiology of sexual dysfunction in this population. Furthermore, an overview of contemporary pharmacological treatments for older men's sexual problems is provided.

Timetable of effects of testosterone administration to hypogonadal men on variables of sex and mood

INTRODUCTION

The effects of testosterone have been extensively characterized, but little attention has been given to the timetable of occurrence of the various effects of testosterone.

METHODS

The timetables of effects on sexual and psychological variables in 40 hypogonadal men receiving treatment with either parenteral testosterone enanthate (TE) or undecanoate (TU).

RESULTS

Sexual thoughts/fantasies and sexual interest/desire/spontaneous morning erections emerged quickly and plateaued after 3 weeks. Total erections rose to a maximum over 9 weeks and then plateaued. Ejaculations per week/satisfaction with sex life rose over the first 3 weeks, increasing steadily to a plateau at 12 weeks. Depression scores decreased to reach a plateau after 6 weeks. Aggressiveness did not change. Scores of concentration improved and reached a plateau after 3 weeks in the group treated with TE and after 9 weeks in the group treated with TU. Good mood improved after 6-9 weeks. Positive effects on self-confidence appeared between 3-6 weeks and on fatigue after 9-12 weeks.

CONCLUSION

Insight into the emergence of effects may be useful information for the patient and for the attending physician in monitoring clinical effects of testosterone treatment of hypogonadal men.

Pharmacogenetics and pharmacogenomics of sexual dysfunction: current status, gaps and potential applications

Although treatment of different types of sexual dysfunction has improved in the past decade with the introduction of phosphodiesterase type 5 inhibitors and selective serotonin reuptake inhibitors, response rates to these targeted therapies are variable. There are a number of studies in the published literature that provide proof-of-concept that genetic variation contributes to the variable response. Pharmacogenomics will most likely be one part of our therapeutic armamentarium in the future and will provide a stronger scientific basis for optimizing drug therapy on the basis of each patient’s genetic constitution. This article will review English language medical literature on the state-of-the-art genetic polymorphisms of drug targets, transporters and signaling molecules as well as pharmacogenetic studies of sexual dysfunction and suggested possible applications. Collectively, the data demonstrate that pharmacogenomics in the field of sexual medicine is still in its infancy. More research will provide further intriguing new discoveries in years to come.

The effect of regular exercise on penile nitric oxide synthase expression in rats

Erectile dysfunction (ED) is a major public health problem that seriously affects the quality of life of patients and their partners and its prevalence increases significantly with ageing. In this study, we tested the hypothesis that age-associated decrease in penile endothelial (eNOS) and neuronal nitric oxide synthase (nNOS) activity in aged rats may be increased by regular exercise. A total of 28 young (4 m) and aged (24 m) male rats were divided into four equal groups: group 1 - young control; group 2 - young trained; group 3 - old control and group 4 - old trained group. Groups 2 and 4 rats were trained to swim for 30 min a day and 5 days a week, which lasted 8 weeks. At the end of 8 weeks, rats were sacrificed and penile tissues evaluated for eNOS and nNOS activities. eNOS and nNOS activities were evaluated by immunohistochemistry in paraffinized penile tissues and results assessed semiquantitatively. Results also were compared with healthy age-matched and adult (4 m) controls. Serum level of testosterone (T) was determined using ELISA kits (Beckman Coulter, Fullerton, CA, USA). In penile tissues of aged control rats, eNOS and nNOS staining were weakly positive; however in trained groups, eNOS and nNOS immunoreactivity were increased. In young control group, eNOS and nNOS activities were more intense than aged control. eNOS and nNOS activities were higher in adult trained group than control. Serum T concentrations were significantly higher in young and aged trained group than in control groups. We can suggest that regular exercise upregulates eNOS and nNOS expressions in the aged and young rat penis. Regular exercise may improve penile erection by increasing penile neurotransmitter in both young and aged rats.

Ginsenoside Rg1 improves male copulatory behavior via nitric oxide/cyclic guanosine monophosphate pathway

INTRODUCTION

Ginsenoside Rg1 is the purified ingredient from ginseng, there has been little research on the effect of Rg1 on male copulatory behavior and its mechanism of action.

AIM

The purpose of this study was to investigate the effect of ginsenoside Rg1 on copulatory behavior of male mice and the mechanism of its action.

METHODS

Male mice were treated with Rg1 intraperitoneally; three elements of copulatory behavior (mounting, intromission, pelvic thrusting) were assessed. After final treatment and behavior determination, nitric oxide (NO) concentration were determined by spectrophotometry method. Plasma testosterone, cyclic guanosine monophosphate (cGMP) in corpus cavernosum both in vivo and in vitro were measured by radioimmunoassay. Rabbit corpus cavernosum segments were incubated with Rg1 (0.05, 0.5 and 5 microM) in the presence of exogenous NO donor sodium nitroprusside (SNP) (10 microM), and the cGMP level was measured. The half maximal inhibitory concentration (IC50) of Rg1 for phosphodiesterase type 5 (PDE5) inhibitors was determined by measuring the conversion of cGMP to 5'-mononucleotides. Sildenafil was set as a positive control. MAIN COME OUT MEASURES: Mounting and intromission frequency, pelvic thrusts, serum testosterone, NO level, cGMP accumulation, IC50 for PDE5.

RESULTS

Rg1 (10 mg/kg) significantly increased mounting and pelvic thrusting frequency and numbers of intromission of male mice from d16 to d20. Rg1 increased serum testosterone concentration, enhanced NO release, and cGMP accumulation in corpus cavernosum both in vivo and in vitro. The IC50 of sildenafil and Rg1 for PDE5 were 4.24 +/- 0.78 and 12.47 +/- 2.31 nmol/L.

CONCLUSIONS

Ginsenoside Rg1 improved copulatory behavior of male mice and this may attribute to its actions at both testosterone level and signal transduction pathway in corpus cavernosum. NO/cGMP pathway appeared to play a key role in mediating the effect of Rg1 on male sexual function. These experimental data provide evidence that Rg1 could be a promising new drug for erectile dysfunction and low libido.