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Inside the cell, NOS catalyzes the oxidation of L-arginine to NO and L-citrulline. Endogenous blockers of this pathway have been identified. The gaseous NO that is produced acts as a neurotransmitter or paracrine messenger. Its biologic half-life is only 5 seconds. NO may act within the cell or diffuse and interact with nearby target cells. In the corpora cavernosa, NO activates guanylate cyclase, which in turn increases cyclic guanosine monophosphate (cGMP). Relaxation of vascular smooth muscles by cGMP leads to vasodilation and increased blood flow.
A good indicator that "everything is in working order" and that it is probably a psychological cause is if a “morning erection” is still experienced. Feelings like fear, anger, distress and anxiety cause part of the nervous system to come into play which directly blocks the action of another part of the system involved in creating an erection. This is a natural reaction – our ancestors would find it more difficult to run from a predator with an erection in the way!
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.
Stress is your body responding to your environment. And it’s a good thing—in limited doses. When you get stressed out your body makes chemicals like adrenaline that make you stronger, faster, fitter, and even able to think more clearly. Most people call this reaction the “fight-or-flight” response, and it’s a life-saver in dangerous situations. In a very real sense, adrenaline makes you a part-time superhero. The problems happen when your body deals with constant stress.
Since endothelial dysfunction, CVD and ED are closely associated in epidemiological studies, the question for clinicians is whether to recommend the man presenting with ED undergo a cardiovascular (CV) evaluation. Clearly, based on numerous studies, ED can be considered at least a ‘marker’ for possible further vascular disease or CVD.15 In their report, Vlachopoulos and coworkers make the point that the man presenting with ED, the clinician, is offered an opportunity to attempt to improve the health of the man by addressing lifestyle modification, and consider further vascular evaluation owing to the clear relationship between endothelial dysfunction, ED and CVD.19
Aging: There are two reasons why older men are more likely to experience erectile dysfunction than younger men. First, older men are more likely to develop diseases (such as heart attacks, angina, cardiovascular disease, strokes, diabetes mellitus, and high blood pressure) that are associated with erectile dysfunction. Second, the aging process alone can cause erectile dysfunction in some men by causing changes in the muscle and tissue within the penis.
Conditions that may be associated with ED include diabetes, [25, 26, 27] hypertension,  , and CAD, as well as neurologic disorders, endocrinopathies, benign prostatic hyperplasia,  , sleep apnea  , COPD,  and depression (see Table 1 below). [32, 33, 34, 35] In fact, almost any disease may affect erectile function by altering the nervous, vascular, or hormonal systems. Various diseases may produce changes in the smooth muscle tissue of the corpora cavernosa or influence the patient’s psychological mood and behavior.
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.
I think that a very powerful argument to young men who want to perform at the highest level is to point out the destructive nature of what they’re doing. If they’re having 18 drinks per week, if they’re having three, four, five drinks at any one time, they’re going to guarantee that their erections are not going to be at the highest level. I can’t tell you the number of men who come in saying, they went out, they had a date, they had a big dinner– which, by the way, is also not a great thing for erections, because all the blood is now going to your gut instead of to the genital area. And how important lifestyle changes are to improving your performance, as well, if not better, than the medications. So make certain that you exercise modestly, not excessively. Make certain that you have a smaller meal on an evening or a day that you want to have a sexual encounter, because you want the blood to go, once again, to the penile area and not to your gut. And really, the whole idea of stress– if you’re stressed out, if you’re worried about a lot of things, if you’re distracted, you can’t initiate that psychic stimulus to your spinal cord and then ultimately to your penis. So stress management is incredibly important.
The role of the endothelium in erectile function became clearer with the observation that the phosphodiesterase type 5 (PDE5) inhibitor, sildenafil, enhanced erectile function. Erection occurs with the release of nitric oxide (NO) from the vascular endothelial cells.17 The reduction in endothelial cell production of NO results in the negative impact on the smooth muscles in the corporal bodies and results in less relaxation of the smooth muscle cells with decrease in blood supply and resulting ED. A similar phenomenon is well known to impact the coronary arterial system resulting in CVD.
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 health care provider will ask about the firmness and duration of erections at different times (e.g., sex with partners, erections after sleep). Discussing sexual dysfunction with a health care provider is very important because many conditions causing it can be successfully treated. If a man has no diseases that cause ED and can have an erection with masturbation or early morning awakening, he likely has ED due to psychological causes.
The appropriate evaluation of all men with erectile dysfunction should include a medical and detailed sexual history (including practices and techniques), a physical examination, a psycho-social evaluation, and basic laboratory studies. When available, a multidisciplinary approach to this evaluation may be desirable. In selected patients, further physiologic or invasive studies may be indicated. A sensitive sexual history, including expectations and motivations, should be obtained from the patient (and sexual partner whenever possible) in an interview conducted by an interested physician or another specially trained professional. A written patient questionnaire may be helpful but is not a substitute for the interview. The sexual history is needed to accurately define the patient's specific complaint and to distinguish between true erectile dysfunction, changes in sexual desire, and orgasmic or ejaculatory disturbances. The patient should be asked specifically about perceptions of his erectile dysfunction, including the nature of onset, frequency, quality, and duration of erections; the presence of nocturnal or morning erections; and his ability to achieve sexual satisfaction. Psychosocial factors related to erectile dysfunction should be probed, including specific situational circumstances, performance anxiety, the nature of sexual relationships, details of current sexual techniques, expectations, motivation for treatment, and the presence of specific discord in the patient's relationship with his sexual partner. The sexual partner's own expectations and perceptions should also be sought since they may have important bearing on diagnosis and treatment recommendations.
Surgery: If neither drugs nor the vacuum pump works, your doctor may suggest surgery. With surgery, the doctor can place a device in your penis that will cause enough hardness for intercourse. In a few cases, infections may develop after the operation, and the doctor may have to remove the device. Another operation that may help you is rebuilding the blood vessels in the penis to increase blood flow into the penis or decrease blood flow out of the penis. These procedures can help you to get and maintain an erection.
#4 You’re just plain turned off. It happens. Whether it’s the weight your partner has put on, the realization that you’re having period sex, or you’re just not getting what you need in the bedroom, at some point in your life, you’re going to be turned off enough to lose *or be unable to attain* your hard-on. [Read: Not attracted to your girlfriend anymore? The why and the fixes]
The pathogenesis of organic ED is related to dysfunction of the endothelium. Endothelial cells can become injured through a variety of mechanisms, most of which cause oxidative stress on the tissues. Many of these causes of oxidative stress are related to lifestyle issues which lead to hypertension, diabetes and dyslipidaemia (figure 1). Endothelial cell dysfunction results in reduction of endothelium-dependent vasorelaxation as well as increased adhesion of leukocytes to the endothelium. Endothelial cell injury then leads to a variety of sequelae, including ED, other types of vasoconstriction, atherosclerosis and thrombus formation.18
So what can you do to help things along a little? Well, chances are it may sort itself out as you settle in to your relationship. But if it keeps happening and you see a future in the relationship, you need to talk about it, or it will soon become the elephant in the bedroom. Pick a time with no distractions and where nobody can overhear you. Tell them that you care about them and that you don’t need to rush things sexually. This can take the pressure off the need to perform.
In men, erectile dysfunction can be defined as being a persistent inability to get or keep an erection that is firm enough to attain sexual satisfaction. It should not be confused with the occasional incident when this occurs, which is an experience common to the vast majority of men for various reasons. These can include having had too much alcohol to drink, being overly-anxious about a new sexual partner, or being worried about current events in your life. The issue would only be classed as Erectile Dysfunction if it keeps happening again and again. Again, an erection once attained should be hard enough and last long enough to be satisfactory. Other conditions, like premature ejaculation, may interfere in this process but these are different problems, and would be treated differently.
In most healthy men, some of the drug will remain in the body for more than two days after a single dose of tadalafil. Metabolism (clearing of the drug from the body) of tadalafil can be slowed by liver disease, kidney disease, and concurrent use of certain medications (such as erythromycin, ketoconazole, and protease inhibitors). Slowed breakdown allows tadalafil to stay in the body longer and potentially increase the risk for side effects. Therefore, doctors have to lower the dose and frequency of tadalafil in the following examples:
The most common inflatable prosthesis is the three-piece penile prosthesis. It is composed of paired cylinders, which doctors surgically insert inside the penis. Patients can expand the cylinders using pressurized fluid (see figure 3). Tubes connect the cylinders to a fluid reservoir and pump, which doctors also surgically implant. The reservoir is usually in the pelvis. A doctor places the pump in the scrotum. By pressing on the pump, sterile fluid transfers from the reservoir into the cylinders in the penis. An erection is produced primarily by expansion of the width of the penis, however, one model can increase in length a small amount also. Lock-out valves in the tubing prevent the fluid from leaving the cylinder until a release valve is pressed. By pressing the relief valve and gently squeezing the penis, the fluid within the cylinders transfers back into the reservoir.
The Latin term impotentia coeundi describes simple inability to insert the penis into the vagina; it is now mostly replaced by more precise terms, such as erectile dysfunction (ED). The study of erectile dysfunction within medicine is covered by andrology, a sub-field within urology. Research indicates that erectile dysfunction is common, and it is suggested that approximately 40% of males with erectile dysfunction or impotence, at least occasionally. The condition is also on occasion called phallic impotence. Its antonym or opposite condition is priapism.
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
All NOS subtypes produce NO, but each may play a different biologic role in various tissues. nNOS and eNOS are considered constitutive forms because they share biochemical features: They are calcium-dependent, they require calmodulin and reduced nicotinamide adenine dinucleotide phosphate for catalytic activity, and they are competitively inhibited by arginine derivatives. nNOS is involved in the regulation of neurotransmission, and eNOS is involved in the regulation of blood flow.
How’s this for a win-win: The more sex you have, the less likely you are to suffer from erectile dysfunction, according to a 2008 study published in The American Journal of Medicine. Men aged 55-75 who reported having sex less than once per week had twice the incidence of erectile dysfunction (there were 79 cases of ED per 1,000) as men who have sex once a week (32 cases of ED per 1,000). But if you really want to up your odds, shoot for three times per week (only 16 cases of ED per 1,000). Can you really argue with science, or a perscription to have more sex?
The most important organic causes of impotence are cardiovascular disease and diabetes, neurological problems (for example, trauma from prostatectomy surgery), hormonal insufficiencies (hypogonadism) and drug side effects. Psychological impotence is where erection or penetration fails due to thoughts or feelings (psychological reasons) rather than physical impossibility; this is somewhat less frequent but can often be helped. In psychological impotence, there is a strong response to placebo treatment.
Healthy lifestyle minimizes risk of ED. Erection depends on blood flow through the penis. Anything that impairs it increases ED risk: smoking, diabetes, high cholesterol, high blood pressure, heart disease, being overweight, sedentary lifestyle, more than two alcoholic drinks a day, and fewer than five daily servings of fruits and vegetables. Avoiding these risk factors does not prevent post-50 erection changes, but it preserves erection function and helps prevent ED.
Tests such as the bulbocavernosus reflex test are used to determine if there is sufficient nerve sensation in the penis. The physician squeezes the glans (head) of the penis, which immediately causes the anus to contract if nerve function is normal. A physician measures the latency between squeeze and contraction by observing the anal sphincter or by feeling it with a gloved finger inserted past the anus.
My fear of this happening has prevented me from getting with girls who aren't randoms in fear that they'll tell people about it. I've been thinking that maybe I should pop a Viagra or something the next time I think I'm gonna get lucky, just to build my confidence a bit, but that's really my last resort. Is there any advice you guys might be able to give me here?
In addition, a man affected by lower testosterone may feel less sexually inclined, less interested in viewing sexual material, and less interested in physical activities. To add to this, a man dealing with less testosterone may also become less assertive, more inclined to stay in, and more likely to seek out medical help for his erectile dysfunction.
Impotence can have emotional causes but most often it is due to a physical problem. The physical causes of impotence include diseases (such as diabetes and hypertension), injuries (such as from prostate surgery), side-effects of drugs (such as the protease inhibitors used in HIV therapy), and disorders (such as atherosclerosis) that impair blood flow in the penis. Impotence is treatable in all age groups. Treatments include psychotherapy, vacuum devices, surgery and, most often today, drug therapy.
There are also alternative treatments, such as using a penis pump or a penile injection. Penis pumps work by creating a vacuum and thereby causing more blood to flow to your penis. Penile injections need to be used shortly before intercourse. They contain a medication which widens your blood vessels. A doctor’s prescription is needed for the injections.
By contrast, psychogenic impotence typically is abrupt in onset, often in relation to psychological trauma, and may wax and wane. Patients with psychogenic impotence may have total erectile failure with one partner but not another, or be impotent during sexual intercourse but not during self-stimulation. Normally occurring spontaneous erections in the morning suggest psychogenic rather than organic causes for impotence.