Low intracavernosal nitric oxide synthase levels are found in people with diabetes, smokers, and men with testosterone deficiency. Interference with oxygen delivery or nitric oxide synthesis can prevent intracavernosal blood pressure from rising to a level sufficient to impede emissary vein outflow, leading to an inability to acquire or sustain rigid erection. Examples include decreased blood flow and inadequate intracavernosal oxygen levels when atherosclerosis involves the hypogastric artery or other feeder vessels and conditions, such as diabetes, that are associated with suboptimal nitric oxide synthase activity.
A thorough history (including cardiovascular symptoms, age, presence of risk factors and comorbid conditions such as obesity, hypertension, dyslipidaemia, pre-diabetes, CAD, peripheral artery disease, symptoms suggestive of sleep apnoea, family history of premature atherothrombotic CVD and lifestyle factors), assessment of ED severity (according to SHIM) and duration, and physical examination (for both heart and peripheral circulation pathology) are mandatory first-line elements of investigation. A resting electrocardiogram, measurement of fasting plasma glucose, and estimation of glomerular filtration rate are desirable tests that may be used to further characterize cardiovascular status and risk and to identify men who require additional cardiologic workup. Owing to the accumulating evidence supporting the link with CVD, the measurement of testosterone is recommended in all men with a diagnosis of organic ED, especially in those for whom phosphodiesterase type 5 (PDE5) inhibitor therapy failed.
After the initiation of TTh patients should be evaluated at 3 and 6 months, and annually thereafter to assess response to treatment and monitor adverse effects. Assessment should include physical examination with particular attention to the prostate. At these intervals testosterone levels should also be monitored, as well as PSA, haematocrit, and HDL.45
Relaxation of erectile tissue requires nitric oxide from nonadrenergic-noncholinergic neurons and the endothelium.21 Penile tissue from diabetic men with ED demonstrates impaired neurogenic and endothelium-mediated relaxation of smooth muscle,22 increased accumulation of advanced glycation end products (AGEs),23 and upregulation arginase, a competitor with nitric oxide synthase for its substrate L-arginine.24 Normal responses to direct smooth muscle relaxants in most of these studies implies that the impairments are due to decreased synthesis, release, or activity of nitric oxide. The fundamental mechanisms mediating these changes are thought to be the same as for other diabetic complications: increased polyol pathway flux, intracellular accumulation of AGEs, activation of protein kinase C, and increased flux through the hexosamine pathway.25

Cardiovascular disease and ED represent 2 common disease processes that are often intimately associated with one another. These common pathophysiological links necessitate a solid scientific and clinical understanding of these 2 disorders and a team effort between the cardiologist and urologist to provide effective management strategies for these patients.
Crossref | Google ScholarSee all References A 1985 study found that ED accounted for 400,000 outpatient visits and 30,000 hospital admissions per year in the United States, with a direct total cost of $146 million.4x4Feldman, HA, Goldstein, I, Hatzichristou, DG, Krane, RJ, and McKinlay, JB. Impotence and its medical and psychosocial correlates: results of the Massachusetts Male Aging Study. J Urol. 1994; 151: 54–61
Abstract | Full Text | Full Text PDF | PubMed | Scopus (24) | Google ScholarSee all References Erectile function relies on the arterial blood supply from the internal pudendal arteries, which are branches of the hypogastric arterial system (Figure 1). Substantial increases in internal pudendal arterial flow result in pressures within the penis that are comparable to systemic arterial levels.12x12Rampin, O and Giuliano, F. Central control of the cardiovascular and erection systems: possible mechanisms and interactions. Am J Cardiol. 2000; 86: 19F–22F
The wide range of prevalence rates noted among the studies can be attributed to a number of factors. First, prevalence rates are affected by the sensitivity and specificity of methods used to assess ED.1 In addition, a number of these studies used medical record review to identify patients with ED, as opposed to anonymous patient reports. It has been shown in other disease states that patients tend to underreport ED when questioned directly by their providers.3 Therefore, the use of validated questionnaires that are either self-administered in an anonymous, neutral setting or administered by an objective third-party interviewer are preferred.
DHEA. Testosterone is essential for a healthy libido and normal sexual function, and erectile dysfunction sufferers known to have low testosterone improve when placed on prescription testosterone replacement therapy. Similarly, studies have shown that taking over-the-counter supplements containing DHEA, a hormone that the body converts to testosterone and estrogen, can help alleviate some cases of ED. But DHEA can cause problems, including suppression of pituitary function, acne, hair loss and its long-term safety is unknown, says McCullough. For this reason, many experts discourage use of the supplements.

Relation between erectile dysfunction prevalence and type of coronary syndrome (A). Time interval (months) between erectile dysfunction and coronary artery disease symptom onset in chronic coronary syndrome according to the number of vessels involved (B). ACS, acute coronary syndrome; CCS, chronic coronary syndrome, G1: ACS and 1-VD; G2: ACS and 2-,3-VD; G3: CCS. VD, vessel disease; C: the control group with normal coronary angiography. With permission from Montorsi et al.15
The medicine causes blood vessels to expand, increasing blood flow in the body and to the penis, thus helping patients to get an erection. Invasive surgeries that involve rods and balloons are also available to patients suffering from ED. While these treatments often come with potential side effects, discomfort and a financial burden, some ED patients may see success with them.
Another oral treatment that has been used with very little success is yohimbine (Yocon, Yohimex). This is an alpha 2 adrenergic receptor blocker that increases cholinergic and decreases adrenergic tone. It stimulates the mid-brain and increases libido. Optimal results occur when used in men with psychogenic ED. Side effects include anxiety and insomnia.

Abstract | Full Text | Full Text PDF | PubMed | Scopus (66) | Google ScholarSee all References Risk of arrythmias after sexual intercourse was evaluated in 82 patients with stable coronary artery disease who were monitored with ambulatory ECG after sexual intercourse.81x81Drory, Y, Fisman, EZ, Shapira, Y, and Pines, A. Ventricular arrhythmias during sexual activity in patients with coronary artery disease. Chest. 1996; 109: 922–924
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Older age. A man’s risk increases past the age of 40, as age is the variable most strongly associated with impotence. This is due to changing hormones, higher risk for heart problems and those affecting circulation, and decreased sexual desire that often occurs with increasing age. For example, based on findings from the National Health and Social Life Survey, it’s been found that “men between 50–60 years old are more than 3 times as likely to experience erection problems and to report low sexual desire compared to men aged 18 to 29 years.” (3)
Tribulus terrestris is a dicotyledonous herbal plant of the Zygophyllaceae family, used to increase serum testosterone levels, which has only been shown in animal studies (40). A prospective, randomized, double blind study of 30 men showed that Tribulus terrestris was not more effective than placebo on improving IIEF scores or serum total testosterone (41). Two accounts of hepato-nephrotoxicity have been reported in young men who ingested high doses of this herbal medication (42,43).
A man needs to try the medicine at least four times before he concludes that it doesn’t work for him. It is unlikely that a man with diabetes who has other medical problems such as high blood pressure, is taking multiple medicines, and has not had sexual intercourse for several years will be able to have an erection adequate for intercourse the first time he takes a pill. Most men need to try the medicine several times before they have the desired results.