Parasympathetic input allows erection by relaxation of trabecular smooth muscle and dilation of the helicine arteries of the penis. This leads to expansion of the lacunar spaces and entrapment of blood by compressing venules against the tunica albuginea, a process referred to as the corporal veno-occlusive mechanism. The tunica albuginea must have sufficient stiffness to compress the venules penetrating it so that venous outflow is blocked and sufficient tumescence and rigidity can occur.
The association between low testosterone and ED is not entirely clear. Although these 2 processes certainly overlap in some instances, they are distinct entities. Some 2-21% of men have both hypogonadism and ED; however, it is unclear to what degree treating the former will improve erectile function.  About 35-40% of men with low testosterone see an improvement in their erections with testosterone replacement; however, almost 65% of these men see no improvement. 
The penis contains three cylinders, the two corpora cavernosa, which are on the top of the penis (see figure 1 below). These two cylinders are involved in erections. The third cylinder contains the urethra, the tube that the urine and ejaculate passes through, runs along the underside of the penis. The corpus spongiosum surrounds the urethra. Spongy tissue that has muscles, fibrous tissues, veins, and arteries within it makes up the corpora cavernosa. The inside of the corpora cavernosa is like a sponge, with potential spaces that can fill with blood and distend (known as sinusoids). A layer of tissue that is like Saran Wrap, called the tunica albuginea, surrounds the corpora. Veins located just under the tunica albuginea drain blood out of the penis.
I have no idea why your boyfriend's junk is stuck in the junkyard. He's just 25, in the prime of his penis. It's fairly rare for a guy that young to go from instant erection to shy willy. One study found that just 2 percent of men experienced erectile dysfunction before the age of 40. If it's a short-term thing, it could be simple: Maybe he just needs to get more sleep or have fewer drinks.
The observation that TRT enhances the efficacy of PDE5 inhibitors in hypogonadal men taking these therapies with suboptimal response to the PDE5 inhibitors alone has been reported.33 In addition, investigators have demonstrated that TRT in hypogonadal men can improve erectile function even without the benefit of PDE5 inhibitors.33 In addition, guidelines for managing ED in hypogonadal men by the European Association of Urology recommend controlling the man to a eugonadal state prior to initiation of PDE5 inhibitor therapy.36 Testosterone measurement consists of a serum specimen which should be ideally obtained in the morning because of the normal diurnal variation of testosterone which is at its peak in the morning. Since TRT is relatively safe, and men can potentially see an improvement in erectile function, it seems prudent to consider this issue when presented with a patient suffering from ED.
In one study, 9.6% reported ‘occasional’ erectile dysfunction, 8.9% reported erectile dysfunction occurring ‘often’, and 18.6% reported erectile dysfunction occurring ‘all the time’. Of these, only 11.6% had received treatment.In another study, only 14.1% of men reported that they had received treatment, despite experiencing erectile dysfunction for longer than 12 months.
Physical examination should include the assessment of male secondary sex characteristics, femoral and lower extremity pulses, and a focused neurologic examination including perianal sensation, anal sphincter tone, and bulbocavernosus reflex. More extensive neurologic tests, including dorsal nerve conduction latencies, evoked potential measurements, and corpora cavernosal electromyography lack normative (control) data and appear at this time to be of limited clinical value. Examination of the genitalia includes evaluation of testis size and consistency, palpation of the shaft of the penis to determine the presence of Peyronie's plaques, and a digital rectal examination of the prostate with assessment of anal sphincter tone.
Impotence: A common problem among men characterized by the consistent inability to sustain an erection sufficient for sexual intercourse or the inability to achieve ejaculation, or both. Impotence can vary. It can involve a total inability to achieve an erection or ejaculation, an inconsistent ability to do so, or a tendency to sustain only very brief erections.
Uncooperative boners might be related to low testosterone, which could be caused by anything from being overweight or stressed to having a chronic health condition, says Paduch. And in men who have taken anabolic steroids, it's not uncommon for them to end up suppressing their natural testosterone production. If you abuse it over a long period of time, you can really mess with your natural testosterone levels, as well as your fertility and erectile function, he says.
Penile blood flow is measured using a Doppler probe and a 2.5 cm blood pressure cuff. Systolic pressures in the right and left corpora cavernosa are measured and the penile–brachial index is calculated taking a ratio of penile systolic pressure to brachial systolic pressure. These measures should be repeated before and after 3 minutes of exercising the pelvic and leg muscles. In normal men, the PBI should be 0.9 or greater. Ratios between 0.7 and 0.9 suggest vascular impotence; a ratio below 0.6 is diagnostic. Pelvic arteriography can be done if revascularization is considered.
In the majority of patients the impotence is organic, though not endocrinologic, and there is no easily remedied cause. These patients require physiologic testing and urologic consultation for specific diagnosis. Likely causes of impotence in this group include vascular and neurologic diseases. These patients are candidates for penile prostheses or, in special cases, for revascularization. Patients interested in surgical approaches should be referred for further testing. There is little to be gained by continuing the work-up of patients who prefer not to have an operation.
An analysis of 14 studies involving more than 90,000 patients with ED confirmed the relation between ED and an increased risk of cardiovascular events and mortality.  Compared with patients without ED, those with ED had a 44% increased risk of cardiovascular events, a 25% increased risk of all-cause mortality, a 62% increased risk of MI, and a 39% increased risk of cerebrovascular events. Treatment of ED, either through lifestyle interventions or by pharmacologic means, may improve prognosis and reduce risk.
Treatment. prostatitis or another acute infection affecting the genitalia can cause temporary impotence that clears up in response to antibiotics. The smooth muscle relaxant sildenafil (viagra) was introduced in 1998 as a treatment for organic impotence. Administration of testosterone may be indicated if low levels of this hormone are found in a blood sample. If impotence is organic and does not respond to other therapies, a penile prosthesis can be implanted; this is usually done surgically by a urologist. Other therapies include the use of vacuum tumescence devices and penile injection of pharmacologic agents that cause dilation.
Sexual functioning involves a complex interaction among biologic, sociocultural, and psychological factors, and the complexity of this interaction makes it difficult to ascertain the clinical etiology of sexual dysfunction. Before any diagnosis of sexual dysfunction is made, problems that are explained by a nonsexual mental disorder or other stressors must first be addressed. Thus, in addition to the criteria for erectile disorder, the following must be considered:
In their extensive review, Bassil and coworkers summarise the benefits and risks, with benefits such as improvement of sexual function, bone density, muscle strength, cognition and overall improvement in quality of life. Among the risks that have been suggested include erythrocytosis, liver toxicity, worsening of sleep apnoea and cardiac function, possibly increasing symptoms of benign prostatic hyperplasia (BPH). They also note that although a possibility of stimulation of prostate cancer has been hypothesised, no scientific or clinical evidence exists to this possible risk.38
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Stress is another factor that can be a cause or effect of ED. If you're stressed at work, at home, and in your relationships, it's going to take a toll on your sexual function. Your mind is elsewhere, and relaxing when you finally make it between the sheets is a long shot. Now you’re stressed because you can’t get it up (talk about the ultimate catch-22), so you're stuck in this sad, frustrating cycle. “ED really affects the psyche of a guy, regardless of the etiology, Gittens says. “If you have a problem getting an erection one night, you’re probably going to be anxious and worried your partner might see you as less of a man the next time you try to get an erection.” There's a pill that will help with this, and it's not promoted on television with middle-aged men in sports cars. It's a damn chill pill.
Erectile dysfunction (ED) affects 50% of men older than 40 years,  exerting substantial effects on quality of life.  This common problem is complex and involves multiple pathways. Penile erections are produced by an integration of physiologic processes involving the central nervous, peripheral nervous, hormonal, and vascular systems. Any abnormality in these systems, whether from medication or disease, has a significant impact on the ability to develop and sustain an erection, ejaculate, and experience orgasm.
The causes of erectile dysfunction include aging, high blood pressure, diabetes mellitus, cigarette smoking, atherosclerosis (hardening of the arteries), depression, nerve or spinal cord damage, medication side effects, alcoholism or other substance (drug) abuse, pelvic surgery including radical prostatectomy, pelvic radiation, penile/perineal/pelvic trauma such as pelvic fracture, Peyronie's disease (a disorder that causes curvature of the penis and sometimes painful erections), and low testosterone levels.
"One couple came to see me, and when I asked the man how long he'd had erectile dysfunction, he told me it had been happening for five years. His wife looked at him and said: 'But this is the first I've heard of this.'" He adds that Viagra-type drugs can mask the problem, and many men still buy them online to avoid talking to their doctor about their difficulties in the bedroom. As a result, their risk of heart attack is never picked up.
Psychosocial problems are important and may cause erectile dysfunction by themselves or together with other causes of erectile dysfunction, such as diabetes and heart disease. Relationships are complicated and many factors cause tensions, which can affect sexual relations. For some men, these problems can become ongoing and it can help to talk through the issue with a skilled counsellor. It is important to know that the longer erectile dysfunction is left untreated, the greater the effect on relationships. This is another reason why early treatment of erectile dysfunction is important.
Many common medications for treating hypertension, depression, and high blood lipids (high cholesterol) can contribute to erectile dysfunction (see above). Treatment of hypertension is an example. There are many different types (classes) of medications for high blood pressure; these include beta-blockers, calcium channel blockers, diuretics (medications that increase urine volume), angiotensin converting enzyme inhibitors (ACE inhibitors), and angiotensin receptor blockers (ARBs). Patients may use these medications alone or in combination to control blood pressure. Some of these medications can cause troubles with erections. For example, Inderal (a beta-blocker) and hydrochlorothiazide (a diuretic) cause erectile dysfunction, while calcium channel blockers and ACE inhibitors do not seem to affect erectile function. On the other hand, other medications (such as angiotensin receptor blockers [ARB] including losartan [Cozaar] and valsartan [Diovan]) may actually help with erections. Therefore, if possible, you may benefit from changing your medications, but this requires approval by your prescribing health care provider.
Conditions associated with reduced nerve and endothelium function (eg, aging, hypertension, smoking, hypercholesterolemia, and diabetes) alter the balance between contraction and relaxation factors (see Pathophysiology). These conditions cause circulatory and structural changes in penile tissues, resulting in arterial insufficiency and defective smooth muscle relaxation. In some patients, sexual dysfunction may be the presenting symptom of these disorders.
A useful and simple way to distinguish between physiological and psychological impotence is to determine whether the patient ever has an erection. If never, the problem is likely to be physiological; if sometimes (however rarely), it could be physiological or psychological. The current diagnostic and statistical manual of mental diseases (DSM-IV) has included a listing for impotence.
Surgery to repair arteries (penile arterial reconstructive surgery) can reduce impotence caused by obstructions that block the flow of blood to the penis. The best candidates for such surgery are young men with discrete blockage of an artery because of a physical injury to the pubic area or a fracture of the pelvis. The procedure is less successful in older men with widespread blockage of arteries.
Vijay Bhat, MD is a board certified internal medicine physician who is passionate about providing quality medical care that’s affordable for patients. He believes that integrating technology and medicine can make healthcare efficient and more accessible. Throughout his training Dr. Bhat was involved with global health initiatives, providing care to underprivileged communities locally and overseas. He’s also been a strong proponent of quality improvement in the medical field. Dr. Bhat graduated with a BS from the University of California Berkeley, and received his medical degree from Stony Brook University in New York. He completed his residency in Internal Medicine at Rutgers Robert Wood Johnson.
Medical conditions, such as hypertension, diabetes mellitus, and cardiovascular disease (CVD), and psychological conditions, such as depression and anxiety, also contribute to sexual dysfunction in middle-aged or elderly men. CVD and hypertension cause a narrowing and hardening of the arteries, leading to reduced blood flow to the corporal bodies, which is essential for achieving an erection. Diabetes is a common aetiology of sexual dysfunction, because it can affect both the blood vessels and the nerves that supply the penis. Men with diabetes are four times more likely to experience ED, and on average, experience ED 15 years earlier than men without diabetes.7 Obesity is also correlated to the development of several types of dysfunction, including a decrease in sex drive and an increase in episodes of ED.8
A lot of guys don’t want to admit it, but not being able to get or keep an erection happens more often than you’d think. Guys usually have trouble getting or keeping an erection when they’re nervous, scared or worried about something. They might be worried about how they’ll “perform,” or they could be feeling guilty about having sex. They might be afraid of getting a sexually transmitted disease (STD), or, if they are with a girl, getting their partner pregnant. Drugs (including some anti-depressants) and alcohol can also prevent you from getting and/or maintaining an erection.
You may already know that lots of hard drugs — like cocaine, heroin, or Oxycontin — can cause sexual problems (though, quite frankly, if you're on cocaine, heroin, or Oxycontin, you have many more pressing concerns to deal with than getting dirrrty). But did you know that sometimes, even pot can inhibit erections? And you thought weed was just a harmless way to enjoy the musical stylings of Pink Floyd. Who knew it could actually mess with one's own pink floyd?
The National Institutes of Health Consensus Development Conference on Impotence was convened to address (1) the prevalence and clinical, psychological, and social impact of erectile dysfunction; (2) the risk factors for erectile dysfunction and how they might be used in preventing its development; (3) the need for and appropriate diagnostic assessment and evaluation of patients with erectile dysfunction; (4) the efficacies and risks of behavioral, pharmacological, surgical, and other treatments for erectile dysfunction; (5) strategies for improving public and professional awareness and knowledge of erectile dysfunction; and (6) future directions for research in prevention, diagnosis, and management of erectile dysfunction. Following 2 days of presentations by experts and discussion by the audience, a consensus panel weighed the evidence and prepared their consensus statement.
Injection therapy involves injecting a substance into the penis to enhance blood flow and cause an erection. The Food and Drug Administration (FDA) approved a drug called alprostadil (Caverject) for this purpose in July of 1995. Alprostadil relaxes smooth muscle tissue to enhance blood flow into the penis. It must be injected shortly before intercourse. Another, similar drug that is sometimes used is papaverine—not yet been approved by the FDA for this use. Either drug may sometimes cause painful erections or priapism (uncomfortable, prolonged erections) that must be treated with a shot of epinephrine.
This consensus development conference on male erectile dysfunction has provided an overview of current knowledge on the prevalence, etiology, pathophysiology, diagnosis, and management of this condition. The growing individual and societal awareness and open acknowledgment of the problem have led to increased interest and resultant explosion of knowledge in each of these areas. Research on this condition has produced many controversies, which also were expressed at this conference. Numerous questions were identified that may serve as foci for future research directions. These will depend on the development of precise agreement among investigators and clinicians in this field on the definition of what constitutes erectile dysfunction, and what factors in its multifaceted nature contribute to its expression. In addition, further investigation of these issues will require collaborative efforts of basic science investigators and clinicians from the spectrum of relevant disciplines and the rigorous application of appropriate research principles in designing studies to obtain further knowledge and to promote understanding of the various aspects of this condition.
Another study compared the response of surgically and medically castrated rabbits to vardenafil with that of control rabbits.  Castrated rabbits did not respond to vardenafil, whereas noncastrated rabbits did respond appropriately. This result suggests that a minimum amount of testosterone is necessary for PDE5 inhibitors to produce an erection.
For the past few months I’ve been dating a lovely man but our relationship is at risk because he can’t get it up. He says he fancies me and always seems turned on. Sometimes he gets hard - but when we try for sex he loses his erection. On the few occasions he has got hard, he doesn’t orgasm. I’ve always been a very sexual person and would like a lot of sex. We’re hardly having any. I find it difficult to orgasm even if he tries other things because I keep thinking. Why can’t he have proper sex with me?
So here’s something that’s really fascinating. Healthy eating is a way to reduce anxiety and stress. Now how, you may be asking, right? Well, think about it. We live in a world where there are so many variables and where we don’t have control over our lives. But now, with healthy eating, we have control over what goes into our body. And now having that control empowers us to be even healthier, to be more directive in what we do. And certainly, that begins then to reduce the anxiety and the stress. So all in one, you have a healthier body, but certainly a healthier mind.