In some cases, ED can be a warning sign of more serious disease. One study suggests ED is a strong predictor of heart attack, stroke, and death from cardiovascular disease. The researchers say all men diagnosed with ED should be evaluated for cardiovascular disease. This does not mean every man with ED will develop heart disease, or that every man with heart disease has ED, but patients should be aware of the link.
Achieving an erection is a complicated process, requiring transmission of sensations from the genital area to the nervous system and the return of nervous impulses to the muscles and blood vessels of the penis. Anything that interferes with this interchange, such as disease or injury of the blood vessels, muscles, or nerves, can make achieving and maintaining an erection difficult. Psychological factors, such as anxiety and depression, can also interfere with erectile function. Anxiety and depression may also develop as a consequence of impotence.
Ejaculatory incompetence, erectile difficulty, erectile dysfunction, erectile failure, frigidity–female Medtalk The inability to achieve or maintain a penile erection adequate for the successful completion of intercourse, terminating in ejaculation; penile erection is mediated by nitric oxide Epidemiology Prevalence of minimal, moderate, and complete impotence in the Massachusetts Male Aging Study was 52%; age is the most important factor; complete impotence ↑ from 5%–age 40 to 15%–age 70; for an erection to achieve a successful outcome, it requires
Since you’re the talker, this is an argument that you’re going to have to win. Really let him know that you feel insecure and unloved when he doesn’t say “I love you.” Tell him it makes you worry about how he really feels when he doesn’t say anything. Tell him that it hurts you that he won’t step the slightest bit out of his comfort zone to say three words that would make you feel so much better. Let him know this doesn’t mean he has to suddenly get all lovey-dovey and give you a cheesy nickname and lay on the sugar so sweet your teeth rot, you adorable little honeybee — because then you might both puke. (I just threw up a little in my mouth myself while typing that.) But that’s not what you’re asking. Let him know you just want an “I love you” now and then. That’s not unreasonable. He doesn’t have to go overboard and you may not get the constant affirmation you prefer — but you can both compromise.
You get to decide what is normal for you. That might include him still experiencing pleasure from you touching his penis even if he’s not hard. Some men can still orgasm without an erection. Or he may prefer not to have any touching while he is dealing with his erection problems. It is okay for you to orgasm even if he doesn’t. Reading about what might bring you pleasure, or considering how you think about sex can make this something enjoyable to explore together.
NO is produced by the enzyme NO synthase (NOS).  NOS plays many roles, ranging from homeostasis to immune system regulation. To date, 3 subtypes have been identified: nNOS, iNOS, and eNOS, which are produced by the genes NOS1, NOS2, and NOS3, respectively. This nomenclature is derived from the sources of the original isolates: neuronal tissue (nNOS), immunoactivated macrophage cell lines (iNOS), and vascular endothelium (eNOS). The subtypes are not, however, limited to the tissues from which they were first isolated.
Stiffy Solution: The good news is, almost all of these conditions can be successfully treated if you catch them early on. And since erectile problems may be the first side effect your dude has experienced, seeking medical treatment for his erectile problems may be the thing to get him into a doctor's office. So if your dude is a well-rested, non-drinking, non-smoking, paragon of relaxation who suddenly can't get wood, urge him to talk to his doctor — his misbehaving penis may actually be communicating something way more important than "Not tonight, honey."
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.
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. 
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.
Stiffy Solution: Luckily, alcohol-induced impotence (also known by the infinitely less classy alias "whiskey d*ck") is a totally temporary condition, one that should clear up as soon as your dude can once again walk a straight line and recite the alphabet backwards. If your dude has consistent erectile problems from consistently drinking too much, however, he should consider cutting down on the sauce, and possibly talking with a doctor.
The laboratory results should be discussed with the patient and, if possible, with his sexual partner. This educational process allows a review of the basic aspects of the anatomy and physiology of the sexual response and an explanation of the possible etiology and associated risk factors (eg, smoking and the use of various medications). Treatment options and their benefits and risks should be discussed. This type of dialogue allows the patient and physician to cooperate in developing an optimal management strategy.
Neurologic impotence is suggested by the absence of sensation in the sacral dermatomes when tested by pinprick, or by neurologic abnormalities elsewhere. The bulbocavernosus reflex may be assumed to be present if anal sphincter tone is normal on rectal examination. If there is doubt, the reflex can be tested by pinching the glans penis and assessing sphincter contraction during the rectal examination.
Yohimbine: The main component of an African tree bark, yohimbine is probably one of the most problematic of all natural remedies for ED. Some research suggests that yohimbine can improve a type of sexual dysfunction that is linked with a drug used to treat depression. However, studies have linked yohimbine to a number of side effects, which can include anxiety, increased blood pressure, and a fast, irregular heartbeat. Like all natural remedies, yohimbine should only be used after advice and under supervision from a doctor.
Lifestyle choices that impair blood circulation can contribute to ED. Smoking, excessive drinking, and drug abuse may damage the blood vessels and reduce blood flow to the penis. Smoking makes men with atherosclerosis particularly vulnerable to ED. Being overweight and getting too little exercise also contribute to ED. Studies indicate that men who exercise regularly have a lower risk of ED.