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.     

The relationship between hypogonadism and erectile dysfunction

It is well known that testosterone enhances sexual interest leading to an increased frequency of sexual acts and an increase in the frequency of sleep-related erections. However, it has little effect on fantasy- or visually induced erections. Exact contribution to erection from testosterone in men remains unclear. Animal studies have well demonstrated that testosterone plays critical physiological (activity of nitric oxide synthases and phosphodiesterases), biochemical (through an endothelial-independent pathway and adrenergic tonicity) and structural (change of fibroelasticity and hollow cell accumulation) roles in erectile function. The supplementation of testosterone to castrated animals can restore erectile function. Clinically, reports of patients with erectile dysfunction (ED) combined with hypogonadism who receive testosterone therapy have inconsistent results. However, testosterone may ameliorate the expression of the phosphodiesterase-5 (PDE5) inhibitor, and the use of testosterone in conjunction with the PDE5 inhibitor revealed convincing results. Because of potential risks in clinical use, testosterone therapy should be individualized, carefully considered and closely monitored, especially, in patients with possible occult prostate cancer, and large benign prostatic hyperplasia. Lower urinary tract symptoms might be worsened by this treatment, since the prostate is an androgen-dependent tissue.     

Prevalence of late-onset hypogonadism in men with type 2 diabetes mellitus

Late-onset hypogonadism (LOH) or age-associated testosterone deficiency syndrome is defined as a clinical and biochemical syndrome associated with advancing age and characterised by symptoms and a deficiency in serum testosterone levels. This condition may result in significant detriment in the quality of life and adversely affect the function of multiple organ systems. It has been suggested that sex steroid hormones may play a causal role in the development of insulin resistance and type II diabetes. This comparative study was aimed at determining the prevalence of LOH in diabetic men with erectile dysfunction and investigating the effect of testosterone replacement therapy on erectile function and on glycaemic control.     

Testosterone levels in men with erectile dysfunction

OBJECTIVE: To investigate the frequency of hypogonadism in men with erectile dysfunction (ED) and to assess which factors are related with low testosterone levels. PATIENTS AND METHODS: In all, 165 men with ED were assessed; the evaluation included: hormonal profiles, serum total and free testosterone (using Vermeulen's formula) levels, and self-reported questionnaires on erectile function and desire domains of the International Index of Erectile Function. The frequency of hypogonadism was established using total and free testosterone levels as diagnostic criteria. The factors that might influence testosterone levels were evaluated by univariate and multivariate statistical analysis, and a logistic regression was used to determine which factors can predict free testosterone levels below normal limits (biochemical hypogonadism). RESULTS: Using the total testosterone levels, 4.8% of the men were hypogonadal, whereas when using the free testosterone levels, 17.6% were hypogonadal. In the univariate analyses, not smoking and hypertension were associated with lower total and free testosterone levels. Ageing, absence of nocturnal erections and a lower erectile function score were only associated with lower free testosterone serum levels. There was no association between total and free testosterone levels and desire. In the multivariate analysis, only total testosterone levels were related to hypertension, while free testosterone levels were related to age and nocturnal erections. For biochemical hypogonadism, simple logistic regression analysis selected age, erectile function score and aetiological diagnosis of ED as predictors. In the multivariate analysis only the erectile function score had significant independent prognostic value. CONCLUSIONS: The frequency of hypogonadism is higher when free testosterone levels are used for diagnosis. The total and free testosterone levels were not related to the level of sexual desire in men with ED. The free testosterone levels could be related to the quality and frequency of nocturnal erections, and when ED is more severe, it is more probable that free testosterone levels are below the 'normal' limit.     

Androgen deficiency in the etiology and treatment of erectile dysfunction

The evaluation and management of erectile dysfunction (ED) has evolved dramatically following the introduction of oral phosphodiesterase-5 inhibitors. Despite the limited role of directed diagnostic testing in the evaluation of the impotent patient, routine de-termination of a serum testosterone likely is indicated based on evidence that testosterone modulates erectile function, that hypogonadism is prevalent among elderly men and men with ED, and that symptomatology alone rarely detects hypogonadism. Forms of testosterone commonly used include oral, parenteral, transdermal, and implantable preparations, each with significant advantages and disadvantages. The risks and benefits of testosterone supplementation have been characterized incompletely and will require further validation before widespread use of testosterone as hormone replacement therapy in aging men.     

Testosterone and erectile dysfunction

Aging is associated with a decline in several important health factors in men, including libido. Serum testosterone concentrations also decrease with age, and many age-related clinical features are closely associated with androgen deficiency, including erectile function (ED). Approximately 70% of ED is of organic origin, with the major risk factors being diabetes mellitus, hypercholesterolemia, smoking and chronic medical illnesses. These are also established risk factors for atherosclerosis, which is the predominant predisposing factor of vasculogenic ED. The introduction of phosphodiasterase-5 (PDE-5) inhibitors for the treatment of ED made a significant impact both in terms of clinical efficacy, and increasing the awareness of the condition. In spite of this, some patients fail to respond to PDE-5 inhibitors alone. Both animal and clinical studies indicate that testosterone therapy improves both erectile function and the response to PDE-5 inhibitors in patients with ED and hypogonadism. Indeed, interventional studies demonstrate that testosterone replacement therapy improves erectile function in hypogonadal men who have previously failed to respond to PDE-5 inhibitors alone. Furthermore, it has been demonstrated that the full therapeutic potential of PDE5 inhibitors will only become manifest in a eugonadal state. Recent studies have demonstrated a close relationship between testosterone and ED and suggest that testosterone therapy may be a valuable option for an increasing number of affected men. European guidelines recommend that all men presenting with ED should have their testosterone concentrations measured.     

Testosterone and Erection: Practical Management for the Patient with Erectile Dysfunction

Although erectile dysfunction (ED) and testosterone deficiency syndrome are two independently distributed disorders, there is a degree of overlap between them. Testosterone replacement therapy, either alone or combined with other treatments such as a phosphodiesterase type 5 (PDE5) inhibitor, may therefore be useful in some men with ED. Corrective treatment of ED includes sex therapy, risk factor modification, chronic usage of PDE5 inhibitors, and testosterone replacement. Studies have shown that testosterone replacement in men with hypogonadism improves libido and erectile function in a significant proportion of cases. If corrective treatment fails or is not indicated, symptomatic treatments such as oral PDE5 inhibitors or intraurethral/intracavernous therapy are available. PDE5 inhibitors are an excellent first-line choice, although a significant proportion of men still fail to respond to monotherapy. Testosterone deficiency may be overlooked in some men with ED and, because this may be associated with lower expression of PDE5 in the penis, it could result in failure of PDE5 inhibitor therapy. Recent recommendations, therefore, suggest the need for combination therapy in some patients. In conclusion, all men presenting with ED should have their testosterone levels checked, and testosterone replacement should be considered in those with low levels. Testosterone replacement should also be considered in hypogonadal men with ED not responding to PDE5 inhibitors. If erections remain insufficient after 3 mo, a combination of testosterone and a PDE5 inhibitor may be beneficial.     

Therapie des „Aging male“

Serum testosterone levels decline in men with increasing age. Late-onset hypogonadism with its characteristic symptoms can occur in men as they age. Typical symptoms of late-onset hypogonadism are decreased libido and sexual function, osteoporosis, altered distribution of body fat, overall reduction in physical strength, and alterations in general mood. Late-onset hypogonadism can be treated with testosterone, and different forms of testosterone have become available for this indication.The aim of testosterone replacement therapy is to produce serum testosterone levels within the physiological range avoiding levels above and below this range. Although hormone replacement therapy has become accepted in aging males, careful consideration of the indications and therapy monitoring are still required since there are major concerns about the long-term outcome of this therapy and particularly its effects on the prostate gland.     

Can testosterone level be a good predictor of late‐onset hypogonadism?

Androgens are essential for the development and growth of the genitalia. They regulate the erectile physiology by multiple mechanisms. Several studies have examined associations among sex hormones' serum levels, erectile function and sex drive. We sought to identify a protocol for using testosterone in men with erectile dysfunction and late‐onset hypogonadism (LOH). During a 16‐month period, men with erectile dysfunction who presented to the andrology clinic were selected. They underwent a complete physical examination and filled out the International Index of Erectile Function‐5 questionnaire. Serum luteinising hormone (LH) and testosterone levels were evaluated. Patients received a single intramuscular injection of 250 mg testosterone. Thereafter, serum levels of LH and testosterone were measured 3 weeks later. The mean age was 53 years old. After treating patients with testosterone, 45 (94%) showed improvement in LOH symptoms including libido, loss of energy, irritability and quality of life. The mean International Index of Erectile Function was 9 and 13.1, prior to and after treatment respectively. Mean serum testosterone levels before and after treatment were 4.2 and 4.1 ng ml^?1 respectively (P = 0.849). Mean serum LH revealed a significant decrease after the study (P = 0.004) (6.12 and 5.1 ng ml^?1, before and after the study respectively). Our findings suggested that testosterone replacement therapy improves libido and LOH symptoms in individuals with almost normal or lower limit normal value of serum testosterone levels.     

Testosterone replacement therapy for late-onset hypogonadism: current trends in Korea

Testosterone levels in men older than 40 years can decrease at a rate of 1%-2% per year, and reports show that more than 50% of 80-year-old men have testosterone levels consistent with hypogonadism. Late-onset hypogonadism (LOH) is a clinical and biochemical syndrome associated with advancing age and characterized by typical symptoms of serum testosterone deficiency. In recent decades, the concept of LOH in ageing men has become familiar in European countries and the United States. It is also a topic of interest and debate throughout Korea. However, most of the data regarding advantages or disadvantages of testosterone replacement therapy (TRT) as treatment for LOH have been primarily obtained from studies on Western populations; therefore, studies of the effects of TRT in Asian men, who may have different serum testosterone compared to Western men, are needed. TRT is commonly prescribed in Korea, despite the paucity of studies on the effects of TRT in Asian populations. Data from various TRT studies based on Korean have shown its efficacy in increasing serum testosterone levels and improving subjective symptoms as assessed by questionnaires. Currently, patches and short-acting intramuscular injections are displaced by gels and long-acting formulations. However, to prevent overdiagnosis and overtreatment, indication for TRT should include both low testosterone levels and symptoms and signs of hypogonadism.     

Testosteronsubstitutionstherapie beim Prostatakarzinom

After the fourth decade of life the total testosterone level in men decreases continually. If clinical symptoms, such as decreased libido or erectile dysfunction are combined with a decreased serum testosterone level this is known as late onset hypogonadism (LOH) or partial androgen deficiency in the aging male (PADAM). In such cases testosterone substitution therapy is indicated. One important question is how to treat patients suffering from LOH but also have prostate cancer which was treated curatively in the past? Only relatively little data are available with small numbers of patients which show that testosterone substitution therapy is possible without an increased risk of a relapse in cases of cured prostate cancer. If the patient was cured it does not matter if radical prostatectomy or radiation therapy was used. It is mandatory that patients are well-informed about substitution therapy and that regular surveillance and controls are carried out during the therapy. For patients who still have prostate cancer which has not yet been treated or not yet cured decisions on whether the benefit of the testosterone replacement is greater than the potential risk of a progress of the disease have to be made on an individual case-specific basis.     

Hypogonadism is associated with overt depression symptoms in men with erectile dysfunction

Depression and hypogonadism are associated with erectile dysfunction (ED). We evaluated the prevalence of both conditions in men presenting to an ED specialty clinic, and tested whether hypogonadism correlated with the presence of depressive symptoms using a validated questionnaire. From July 2001 to June 2003, 157 men referred to an ED specialty clinic prospectively filled the Center for Epidemiologic Studies Depression Scale (CES-D), the abbreviated International Index of Erectile Function (IIEF-5) and had testosterone serum levels drawn. Median age was 53 (range=21-85 years). Hypogonadism, defined as serum T (testosterone)<300 mg/dl, was present in 36% of patients. This proportion was higher in men over the median age compared to younger patients (45 and 26%, respectively, P=0.002). Overt depression symptoms, defined as a CES-D> or =22, were found in 24% of men. Mean age of men with overt depression was 49.9+/-10.1 years vs 55.1+/-15.8 years for those with CES-D<22 (P=0.02). Hypogonadal men were more likely to have overt depression scores compared to eugonadal counterparts (35 vs 18%, P=0.02). This association was statistically stronger after correcting for age in a multivariate linear model (P=0.005). The relative risk of having overt depression was 1.94 times higher in men with hypogonadal testosterone level (95% confidence interval: 1.13 to 3.7). We conclude that in an ED referral population, symptoms of hypogonadism and depression symptoms are fairly prevalent, and that overt depression symptoms are strongly associated with hypogonadism. Clinicians should consider testosterone measurements in all men with high depression symptom scores.     

Significance of hypogonadism in erectile dysfunction

To review the role and significance of hypogonadism, defined as a low testosterone (T) level, in erectile dysfunction (ED). Review of literature. Serum T is below 3 ng/ml in 12% of ED patients, including 4% before and 15% after the age of 50. Replacement studies in men with severe hypogonadism demonstrate that sexual desire and arousal, as well as the frequency of sexual activity and spontaneous erections are clearly T-dependant. Psychic erections are partly T-dependant. The effects of T upon sexual function are dose-dependant up to a threshold level that is consistent within an individual, but markedly variable between individuals, ranging from 2 to 4.5 ng/ml. More evidence is required to confirm a significant impact of T on the intrapenile vascular mechanisms of erections in men as it is the case in animals. No convincing association of T with ED has been found in epidemiological studies. As concerns clinical experience, although a meta-analysis of the randomized controlled trials established that T therapy consistently restores erectile function in young hypogonadal patients with T below 3.46 ng/ml, the effects of this treatment have been mostly disappointing when used alone in older patients consulting for ED who are subsequently diagnosed to have hypogonadism following routine T measurement. These poor results may probably be explained by the high prevalence of co-morbidities, and by the fact that ED itself may induce hypogonadism. Combination therapy with T and PDE5 inhibitor (PDE5I) may be effective in the hypogonadal ED patients when T therapy alone fails. However, more evidence is required to confirm the hypothesis that a minimum level of T is required for a complete effect of PDE5I in certain men, since a PDE5I was able to restore complete erections in severely hypogonadal men. Though a low T level is not always the only cause of ED in hypogonadal ED patients, there are important benefits in screening for hypogonadism in ED. A low T level justifies a 3 month trial of T therapy, before combining a PDE5I if T therapy alone fails     

Diagnosis of hypogonadism in patients treated with low energy shock wave therapy for erectile dysfunction: a narrative review

Several methods of treatment of erectile dysfunction (ED) are offered with low energy shock-wave therapy (LESWT) gaining increasing attention. Reports have documented that LESWT stimulates tissue neovascularization, proliferation and differentiation of endothelial cells, and production of nitric oxide - all can improve the condition of erectile tissue. However, the overall and sexual condition of men deteriorates with age which is linked with a constant decrease in testosterone concentration. A higher risk of sexual health disorders and reduced physical fitness correlates with a testosterone concentration of <12 nmol/L. Such patients may require testosterone replacement therapy. We conducted a target literature review to investigate whether testosterone concentration is taken into account in studies on the use of LESWT in the treatment of ED. We found that most studies did not provide any information on testosterone status. Only 8 of 25 studies examined showed values of testosterone concentrations. Only one of these analyses checked the relationship between the efficacy of LESWT and testosterone concentration. As a result, meta-analyses published to date may not show the full value of LESWT in the treatment of ED. We conclude that in the light of the significant role testosterone plays in the process of an erection and the mechanism of LESWT action, it can be recommended to examine testosterone concentration and to diagnose hypogonadism during the qualification of patients to studies on LESWT efficacy. Moreover, the effectiveness of LESWT in relation to the current testosterone concentration should also be further investigated.     

Hypogonadism in the man with erectile dysfunction: What to look for and when to treat

Hypogonadism (low serum testosterone) is commonly associated with erectile dysfunction (ED). However, many urologists may lack appreciation of the relative merits of treating hypogonadism compared with oral phosphodiesterase inhibitors for sexual dysfunction. Testosterone-replacement therapy (TRT) may be the best treatment for men with ED when the presentation includes diminished libido or other sexual symptoms or when non-sexual symptoms such as depressed mood, decreased sense of vitality, and increased fatigue also exist. The health benefits of TRT also include improvements in body composition, bone density, cognition, and sense of well-being. Thus, there may be good reasons to use TRT as first-line therapy for the man with ED. Concerns regarding prostatic and cardiovascular risks of TRT have not been supported by the literature. Nevertheless, men receiving TRT must be monitored at regular intervals with digital rectal examination and blood testing for prostate-specific antigen. Hematocrit or hemoglobin also should be obtained regularly due to the risk of erythrocytosis. Awareness of the benefits of TRT in the man with ED may improve clinical outcomes.     

Prevalence and management of mild hypogonadism: introduction

Although male hypogonadism can adversely affect the well-being of otherwise healthy men, physicians sometimes overlook it as a possible contributing factor to decreased libido, erectile dysfunction (ED), irritability, osteoporosis, and decreased muscle mass. However, hypogonadism is easily treated by testosterone replacement therapy, which may provide benefits such as mood improvement, increased bone density, and possibly reduced risk of type II diabetes. Articles in this supplement focus on populations that may benefit from testosterone replacement therapy (eg, men with type II diabetes, HIV, and ED). An overview of male 'andropause' is also provided. The authors discuss the surprisingly high prevalence of hypogonadism in certain patient populations and its impact on quality of life. Although testosterone has been used therapeutically for years, much remains to be learn about this hormone and its positive effects.     

Sexual functions of men with obstructive sleep apnoea syndrome and hypogonadism may improve upon testosterone administration: a pilot study

This study examined 72 patients with obstructive sleep apnoea syndrome (OSAS), confirmed by polysomnography. Thirty-two patients were suffering from erectile dysfunction (ED) assessed by IIEF-5 questionnaires and confirmed by nocturnal penile tumescence examination. Their testosterone levels were measured. Eight patients had normal testosterone levels and were treated with a PDE-5 inhibitor (vardenafil) only; after 6 months of treatment, 6 of these patients (75%) showed significant improvement in erectile function. The remaining 24 patients with OSAS, ED and hypogonadism (total testosterone <12 nmol l⁻¹), were divided into two groups based on the indication for continuous positive airway pressure (CPAP) therapy: five patients received CPAP therapy (group 1) and 19 patients did not (group 2). The patients of group 2 received only a PDE-5 inhibitor (vardenafil 20 mg) for ED; and eight patients (42%) showed an improvement after 3 months of treatment. The five patients receiving CPAP therapy were treated with a combination of parenteral testosterone undecanoate and a PDE-5 inhibitor (vardenafil) and all had normal erectile function after 3 months of therapy. The results suggest positive effects of addition of testosterone to treatment with PDE-5 inhibitors in hypogonadal men with OSAS, which should be confirmed in larger controlled studies.     

Testosteronsubstitutionstherapie beim Prostatakarzinom

During the male 40s total testosterone levels decrease continuously. If clinical symptoms like decreasing libido, erectile dysfunction, osteoporosis, altered distribution of body fat, reduction in physical strength, or alterations in psychological mood are combined with a decreased serum testosterone level late-onset hypogonadism (LOH) is obvious. Before the substitution of testosterone is initiated, it is essential to exclude prostate cancer because the progress of prostate cancer depends on androgens. The question is now how to treat patients who suffer from androgen deficiency but have cured prostate cancer in their history? Concerning this there are only a few studies with a small number of patients which show that testosterone substitution therapy is possible without an increased risk for recurrence of prostate cancer. As long as the patient was cured it does not matter if he underwent a radical prostatectomy or brachytherapy. Absolutely necessary is that the patient is well informed about the therapy and regularly controlled during the therapy.     

Obesity, low testosterone levels and erectile dysfunction

Obesity is an important risk factor for many common diseases including cardiovascular disease (CVD), type 2 diabetes, cancer and erectile dysfunction (ED). Adipose tissues produce a number of adipokines and cytokines, which affect endothelial and metabolic function resulting in insulin resistance and the metabolic syndrome (risks factors for CVD). Both ED and metabolic syndrome improve with a reduction in body mass index (BMI). The relationships among obesity, metabolic syndrome, ED, sex hormone-binding globulin (SHBG) and serum total and free testosterone levels are complex and often confusing to the physician. It is known that BMI is inversely proportional to serum total testosterone concentrations; low serum SHBG levels in obesity contribute to the low serum total testosterone. Recent studies show that BMI is also inversely proportional to free testosterone concentration. The characteristic low serum testosterone concentrations observed in obese men are also present in men with the metabolic syndrome and type 2 diabetes mellitus. A small proportion of men with ED have hypogonadism; however, the proportion increases if these men are obese with manifestations of the metabolic syndrome or type 2 diabetes mellitus. ED is a common symptom in patients with type 2 diabetes who also have low testosterone levels. This review describes the relationships between low serum testosterone concentrations and ED in obese patients and those with metabolic syndrome and type 2 diabetes mellitus.     

Following the common association between testosterone deficiency and diabetes mellitus, can testosterone be regarded as a new therapy for diabetes?

Type 2 diabetes mellitus (T2DM) is increasing at epidemic proportions worldwide, representing a risk factor for cardiovascular diseases. Nowadays, hypogonadism and erectile dysfunction (ED) are considered frequent, although often under-diagnosed, complications of T2DM. Recent evidence suggests that in a diabetic population ED itself is an efficient predictor of silent coronary heart diseases. Patients with T2DM have an impaired sexual life, which is worsened by hypogonadism. Low T in T2DM is in fact associated with more severe ED, hypoactive sexual desire and low intercourse frequency. Testosterone replacement therapy (TRT) has been proven to improve sexual function in hypogonadal men. In addition, TRT improves adiposity, insulin resistance and total cholesterol. Specific studies on the effect of TRT in T2DM are scanty. This review will evaluate the contribution of low testosterone in diabetic subjects with sexual dysfunction. In addition, we have also reviewed available evidence on potential metabolic benefits of testosterone supplementation in T2DM patients.