Erectile dysfunction (ED) is the inability to get an erection or to keep one that's firm enough or that lasts long enough for a man to have a satisfying sexual experience. Occasional bouts of ED aren't unusual. In fact, as many as one in five men deal with erectile dysfunction to some degree. Symptoms, of course, are rather obvious. And while age can be a risk factor, so can medication use, health conditions, lifestyle factors (like smoking), and other concerns. Treatment is available and may involve prescriptions, habit changes, or other options.
5. Medline Plus. US National Library of Medicine. NIH National Institutes of Health. Drugs that may cause impotence (updated 21 Jan 2015). http://www.nlm.nih.gov/medlineplus/ency/article/004024.htm (accessed Nov 2016). myDr myDr provides comprehensive Australian health and medical information, images and tools covering symptoms, diseases, tests, medicines and treatments, and nutrition and fitness.Related ArticlesImpotence treatmentsIf you have impotence (erectile dysfunction), the treatment your doctor recommends will depend on thErectile dysfunction: visiting your doctorFind out what questions a doctor may ask when discussing erectile dysfunction (ED, or impotenceGum disease linked to erectile dysfunctionAdvanced gum disease (periodontitis) has been linked to an increased risk of erectile dysfunction, wPeyronie's diseasePeyronie’s disease is condition where a band of scar tissue forms in the penis, causing aAdvertisement
Diabetes is an example of an endocrine disease that can cause a person to experience impotence. Diabetes affects the body’s ability to utilize the hormone insulin. One of the side effects associated with chronic diabetes is nerve damage. This affects penis sensations. Other complications associated with diabetes are impaired blood flow and hormone levels. Both of these factors can contribute to impotence.
Important future developments will include selective androgen receptor modulators (SARMs). These drugs will be able to produce isolated effects of testosterone at androgen receptors. They are likely to become useful clinical drugs, but their initial worth may lie in facilitating research into the relative importance of testosterone’s action at the androgen receptor compared to at other sites or after conversion to other hormones. Testosterone will remain the treatment of choice for late onset hypogonadism for some time to come.
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.
Hypogonadism is a disease in which the body is unable to produce normal amounts of testosterone due to a problem with the testicles or with the pituitary gland that controls the testicles. Testosterone replacement therapy can improve the signs and symptoms of low testosterone in these men. Doctors may prescribe testosterone as injections, pellets, patches or gels.
The medications are extremely effective, which is very good. And the medications are, for the most part, extremely well-tolerated. But there are, like with any medications, a potential downside. The one absolute downside to the use of any of these erection what we call PDE5 medications is if a patient is using a nitroglycerin medication. And nitroglycerins are used for heart disease and for angina, for the most part, although there are some recreational uses of nitrites. And that’s important because your blood vessels will dilate and your blood pressure will drop. And that is an absolute contraindication.
Male hypogonadism is a clinical syndrome caused by a lack of androgens or their action. Causes of hypogonadism may reflect abnormalities of the hypothalamus, pituitary, testes or target tissues. Increases in the amount of testosterone converted to estrogen under the action of the enzyme aromatase may also contribute to hypogonadism. Most aspects of the clinical syndrome are unrelated to the location of the cause. A greater factor in the production of a clinical syndrome is the age of onset. The development of hypogonadism with aging is known as late-onset hypogonadism and is characterised by loss of vitality, fatigue, loss of libido, erectile dysfunction, somnolence, depression and poor concentration. Hypogonadal ageing men also gain fat mass and lose bone mass, muscle mass and strength.
Additionally, the physiologic processes involving erections begin at the genetic level. Certain genes become activated at critical times to produce proteins vital to sustaining this pathway. Some researchers have focused on identifying particular genes that place men at risk for ED. At present, these studies are limited to animal models, and little success has been reported to date.  Nevertheless, this research has given rise to many new treatment targets and a better understanding of the entire process.
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.
You may find this hard to believe, but some common breakfast foods like Kellogg’s corn flakes and Graham crackers were invented 100 years ago to lower male libido. Kellogg and Graham believed that male sexual desire was the root of society’s problems, so they set out to make bland foods that would take away libido (this is absolutely true; look it up). That low fat, grain-based thing absolutely works wonders for lowering testosterone.
Cosgrove et al reported a higher rate of sexual dysfunction in veterans with posttraumatic stress disorder (PTSD) than in veterans who did not develop this problem.  The domains on the International Index of Erectile Function (IIEF) questionnaire that demonstrated the most change included overall sexual satisfaction and erectile function. [43, 44] Men with PTSD should be evaluated and treated if they have sexual dysfunction.
Both ED and low testosterone (hypogonadism) increase with age. The incidence of the latter is 40% in men aged 45 years and older.  Testosterone is known to be important in mood, cognition, vitality, bone health, and muscle and fat composition. It also plays a key role in sexual dysfunction (eg, low libido, poor erection quality, ejaculatory or orgasmic dysfunction, reduced spontaneous erections, or reduced sexual activity). 
The PDE5 inhibitors sildenafil (Viagra), vardenafil (Levitra) and tadalafil (Cialis) are prescription drugs which are taken orally.:20–21 Additionally, a cream combining alprostadil with the permeation enhancer DDAIP has been approved in Canada as a first line treatment for erectile dysfunction. Penile injections, on the other hand, can involve one of the following medications: papaverine, phentolamine, and prostaglandin E1.:25
The FDA recommends that men follow general precautions before taking a medication for ED. Men who are taking medications that contain nitrates, such as nitroglycerin, should NOT use these medications. Taking nitrates with one of these medications can lower blood pressure too much. In addition, men who take tadalafil or vardenfil should use alpha blockers with care and only as instructed by their physician, as they could result in hypotension (abnormally low blood pressure). Experts recommend that men have a complete medical history and physical examination to determine the cause of ED. Men should tell their doctor about all the medications they are taking, including over-the-counter medications.
The Food and Drug Administration (FDA) does not recommend alternative therapies to treat sexual dysfunction. Many products are advertised as "herbal viagra" or "natural" sexual enhancement products, but no clinical trials or scientific studies support the effectiveness of these products for the treatment of ED, and synthetic chemical compounds similar to sildenafil have been found as adulterants in many of these products. The FDA has warned consumers that any sexual enhancement product that claims to work as well as prescription products is likely to contain such a contaminant.
Patients with both ED and cardiovascular disease who receive treatment with an oral PDE5 inhibitor require education regarding what to do if anginal episodes develop while the drug is in their system. Such education includes stressing the importance of alerting emergency care providers to the presence of the drug so that nitrate treatment is avoided.
Epidemiological evidence supports a link between testosterone and glucose metabolism. Studies in non-diabetic men have found an inverse correlation of total or free testosterone with glucose and insulin levels (Simon et al 1992; Haffner et al 1994) and studies show lower testosterone levels in patients with the metabolic syndrome (Laaksonen et al 2003; Muller et al 2005; Kupelian et al 2006) or diabetes (Barrett-Connor 1992; Andersson et al 1994; Rhoden et al 2005). A study of patients with type 2 diabetes using measurement of serum free testosterone by the gold standard method of equilibrium dialysis, found a 33% prevalence of biochemical hypogonadism (Dhindsa et al 2004). The Barnsley study demonstrated a high prevalence of clinical and biochemical hypogonadism with 19% having total testosterone levels below 8 nmol/l and a further 25% between 8–12 nmol/l (Kapoor, Aldred et al 2007). There are also a number longitudinal studies linking low serum testosterone levels to the future development of the metabolic syndrome (Laaksonen et al 2004) or type 2 diabetes (Haffner et al 1996; Tibblin et al 1996; Stellato et al 2000; Oh et al 2002; Laaksonen et al 2004), indicating a possible role of hypogonadism in the pathogenesis of type 2 diabetes in men. Alternatively, it has been postulated that obesity may be the common link between low testosterone levels and insulin resistance, diabetes and cardiovascular disease (Phillips et al 2003; Kapoor et al 2005). With regard to this hypothesis, study findings vary as to whether the association of testosterone with diabetes occurs independently of obesity (Haffner et al 1996; Laaksonen et al 2003; Rhoden et al 2005).
Erections occur in response to tactile, olfactory, and visual stimuli. The ability to achieve and maintain a full erection depends not only on the penile portion of the process but also on the status of the peripheral nerves, the integrity of the vascular supply, and biochemical events within the corpora. The autonomic nervous system is involved in erection, orgasm, and tumescence. The parasympathetic nervous system is primarily involved in sustaining and maintaining an erection, which is derived from S2-S4 nerve roots.