Now that we better appreciate the complex sequence of events necessary for erections to occur, it’s no surprise that testosterone alone yields less than perfect results. Erectile dysfunction represents more than just low testosterone, which is just one facet of the spectrum of dysfunctional phenomena that cause sexual dysfunction. Nonetheless, when testosterone is combined with popular drugs like Viagra®, success is enhanced to an even greater degree—orgasmic function improves, along with erectile capacity and libido.20 Testosterone also activates penile nitric oxide; ultrasound studies have demonstrated a 27% increase in arterial blood flow into the penis with testosterone supplementation.23
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.

Erne P,  Schoenenberger AW,  Zuber M,  Burckhardt D,  Kiowski W,  Dubach P,  Resink T,  Pfisterer M. Effects of anti-ischaemic drug therapy in silent myocardial ischaemia type I: the Swiss Interventional Study on Silent Ischaemia type I (SWISSI I): a randomized, controlled pilot study, Eur Heart J , 2007, vol. 28 (pg. 2110-2117)

While additional investigation is usually necessary, the medical and sexual history is essential and frequently the most revealing aspect of the ED assessment process. Questionnaires are an integral part of the history. The International Index of Erectile Function (IIEF), a 15-item, self-evaluation questionnaire is a validated instrument for assessing erectile function, orgasmic function, desire and satisfaction after sexual relations.8 An abridged version of the IIEF is a 5-item questionnaire the Sexual Health Inventory for Men (SHIM) or IIEF-5 (Table 2). Responses to the five questions range from 1 (worst) to 5 (best). Questions 2 to 4 may be graded 0 (if there is no sexual activity, or no sexual intercourse attempt) and the final score ranges from 1 to 25 points; a descending score indicates worsening of erectile function, with values ≤21 being diagnostic of ED.8 Importantly, validated questionnaires correlate with the extend of CAD9 and improve the predictive value of ED for total cardiovascular events compared with a single-question ED diagnosis.5 It cannot be overemphasized that the SHIM can be effectively used not only by andrologists and urologists but by a wide array of medical specialists, such as cardiologists, diabetologists, primary care physicians, etc.
In subsequent clinical studies, a surprisingly high percentage of EDDM patients–10% to 20%–claimed that the placebo "improved my erections," thus indicating a psychological basis for their ED. In the latter half of the 1980s, objective means were developed that could help determine if a EDDM patient had organic or psychogenic ED. The absence of rigid sleep erections confirmed by penile monitors was one criterion for organic ED. The failure of vasoactive agents (papaverine, Trimix, or prostaglandin E-1 [PGE-1]) injected into the corpora cavernosa to induce penile rigidity was another criterion for organic disease. Intracavernosal maintenance flow rates during pharmacocavernosometry and maximum cavernosal arterial flow during penile Doppler ultrasonography were additional determinants.
Intracavernosal and intraurethral injections are second-line therapy for patients with ED. Alprostadil is the agent most commonly used for intracavernosal injections. The main adverse effects of intracavernosal injections are painful erection, priapism and development of scarring at the injection site.73 Alprostadil is also available as a topical cream in patients who cannot tolerate injections.75
Crossref | PubMed | Google ScholarSee all References After controlling for age, trauma, hypertension, and diabetes mellitus, a study of 97 young patients with ED who underwent selective pudendal angiography showed a significant relationship between lifetime cigarette smoking and the degree of internal pudendal and common penile arterial atherosclerosis.28x28Rosen, MP, Greenfield, AJ, Walker, TG et al. Cigarette smoking: an independent risk factor for atherosclerosis in the hypogastric-cavernous arterial bed of men with arteriogenic impotence. J Urol. 1991; 145: 759–763
Severe testosterone deficiency, known as “hypogonadism,” is present in approximately 2–35% of men with erectile dysfunction.19 However, lesser degrees of deficiency are common, perhaps present in the majority, depending on the definition of “low” applied, the method of measurement, and the parameter being used to define testosterone (total, free, or bioavailable) deficiency.19,20 Most authorities agree that a total testosterone level below 300 ng/dL is clearly low, and that 300–400 ng/dL is low to low-to-normal. Most studies using testosterone replacement for erectile dysfunction have attempted to achieve blood levels of 450–850 ng/dL.
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.
A collection of risk factors that strongly predict heart disease—termed the metabolic syndrome—is also associated with erectile dysfunction. An increasingly prevalent condition, this syndrome includes low HDL, increased triglycerides, high blood sugar, and heightened inflammation and causes a three-fold or greater risk of heart attack, stroke, and diabetes. It is largely attributable to excess weight, poor diet, and inactivity and afflicts at least 47 million Americans, signaling that an epidemic of erectile dysfunction is sure to follow. Indeed, a survey of 2,400 men participating in a health screening revealed that metabolic syndrome increases the likelihood of erectile dysfunction by 48%.10
In many of these cases, a discussion between the physician, the man with erectile dysfunction, and possibly his partner can help to resolve the issues leading to treatment failure. For men who experience severe side effects, can’t take the drugs for other reasons (such as taking medicines such as nitroglycerin), or don’t respond in spite of further education on the correct use of the drugs, there are other treatment options that can help most men remain sexually active.