Few simple laboratory tests can help identify obvious causes of organic ED. Initial labs should include HbA1c, free testosterone, thyroid function tests, and prolactin levels. However, patients who do not respond to pharmacological therapy or who may be candidates for surgical treatment may require more in-depth testing, including nocturnal penile tumescence testing, duplex Doppler imaging, somatosensory evoked potentials, or pudendal artery angiography.
In some cases, however, these drugs may be unsuitable for patients with heart disease. If you are considering one of these drugs and you have heart disease, as many diabetics do, be sure to tell your doctor. In rare cases, the pills may create “priapism,” a prolonged and painful erection lasting six hours or more (although reversible with prompt medical attention).

Neurologic illnesses leading to ED have been recently reviewed (64). The most common of them (i.e., consequences of prostatic surgery, stroke and Parkinson’s disease) are not typical of younger age and, similarly to conditions less common but more typical of younger men, such as spinal cord injury, multiple sclerosis and spina bifida, the clinical features of the underlying disease are clearly apparent, being ED one of the multiple manifestations, rather than a harbinger of a subtle condition. Diagnosis of neurologic origin of ED is often quite simple, based on medical history and physical exam. The clinical management is a multidimensional and coordinated work of rehabilitation and medical therapy, which includes ICI injection of vaso-relaxant drugs, vacuum device and surgery (64).
Monitoring erections that occur during sleep (nocturnal penile tumescence) can help you and your doctor to understand if the erectile dysfunction is due to psychological or physical causes. The nocturnal penile tumescence test is a study to evaluate erections at night. Normally men have three to five erections per eight hours of sleep. The test can be performed at home or in a sleep lab. The most accurate way to perform the test involves a special device that is connected to two rings. The rings are placed around the penis, one at the tip of the penis and the other at the bottom (base) of the penis. The device records how many erections occur, how long they last, and how rigid they are. The test is limited in that it does not assess the ability to penetrate.
High cholesterol and triglyceride levels increase the risk of cardiovascular disease. Getting your cholesterol and triglyceride levels in an optimal range will help protect your heart and blood vessels. Cholesterol management may include lifestyle interventions (diet and exercise) as well as medications to get your total cholesterol, LDL, HDL, and triglycerides in an optimal range.
Additionally, speaking to more than just the sexual issues related to erectile dysfunction, the research addresses implications related to the overall understanding of penile health. According to Arthur Burnett, M.D., a professor of urology and head of the research team, "eNOS plays roles in both immediate erectile response and the overall health and function of the penile tissue." 
Alprostadil should not be used in men at higher risk for priapism (erection lasting longer than six hours) including men with sickle cell anemia, thrombocytopenia (low platelet count), polycythemia (increased red blood cell count), multiple myeloma (a cancer of the white blood cells), and is contraindicated in men prone to venous thrombosis (blood clots in the veins) or hyperviscosity syndrome who are at increased risk for priapism.
Diabetes is one of the most common causes of ED. Men who have Diabetes are three times more likely to have Erectile Dysfunction than men who do not have Diabetes. Among men with ED, those with Diabetes are likely to have experienced the problem as much as 10 to 15 years earlier than men without Diabetes. A recent study of a clinic population revealed that 5% of the men with ED also had undiagnosed Diabetes. The risk of ED increases with the number of years you have Diabetes and the severity of your Diabetes. Even though 20% to 75% of men with Diabetes have ED, it can be successfully managed in almost all men.
Erectile function can be impaired in several endocrine disorders and treating these conditions can improve ED (43). This is the case of adrenal insufficiency, whose treatment with glucocorticoid and mineralocorticoid replacement is able to improve erectile function (44). Similarly, an adequate control of thyroid function in hyper- and hypothyroid patients is associated with an improvement in ED (45,46). However, although ED is a common complaint in subjects with Addison’s disease, hypo- and even more hyperthyroidism (45-48), the prevalence of these disorders is subjects with ED is not so high for recommending the routine screening of adrenal and thyroid hormone in these men (49). In contrast with the low prevalence of adrenal or thyroid disturbances in ED subjects, testosterone (T) deficiency is frequently found in subjects with ED (49,50) and, in turn, low T is frequently associated with the occurrence of sexual dysfunctions, including ED, even in general population (51). Accordingly, the Fourth ICSM recommends the routine assessment of T levels in patients with ED (43). The assessment of prolactin (PRL) in ED patients is controversial because an actual pathological increase in PRL levels (severe hyperprolactinemia: prolactin ≥735 mU/L or 35 ng/mL) is rarely found in ED men (52). Furthermore, the role of PRL in inducing ED is still not clarified. Hyperprolactinemia has been consistently associated with loss of sexual desire (43,53) and development of hypogonadotropic hypogonadism, both conditions that can in turn induce ED. However, a direct role of high PRL levels in inducing an impairment of erectile function is not consistently proven (52,54) and, conversely, more recent evidence suggests that lower, rather than higher, PRL levels are associated with impaired erectile function (55-57). For these reasons, at present, the assessment of PRL levels in subjects with ED is not routinely recommended (43) and it could be advisable only in men with hypogonadotropic hypogonadism, as a possible cause of this condition.
The number of symptoms reported appeared to be a function of the amount of alcoholic beverage consumed. The chance of developing sexual dysfunctions appears to increase with increasing quantity of alcohol consumed. Higher levels of alcohol intake may result in greater neurotoxic effects. It has been reported that heavy alcohol use may contribute to a reversible vagal neuropathy, which is perhaps reversible on abstinence.[17] However, chronic heavy use of alcohol is also known to significantly alter gonadal hormones.[9]
This man’s history is adequate to rule out arterial or venous insufficiency as he can masturbate to produce a rigid, sustainable erection and he responds well to tadalafil. Due to his report of gradual onset, his lack of response to ongoing sexual therapy, and his tremendous anxiety associated with the issue, the decision was made to offer a PCDU to assess for a vascular etiology for his disorder. PCDU revealed normal peak flow bilaterally of 40 cm/sec with no end diastolic flow and 100% rigidity obtained. His erection lasted more than 2 hours and required phenylephrine to resolve the erection.
In patients with low testosterone, testosterone treatment can improve libido and erectile dysfunction, but many men still may need additional oral medications such as sildenafil, vardenafil, or tadalafil. Some studies suggest that men with ED and low testosterone may respond better to PDE5 inhibitors when given testosterone therapy; however, this is controversial.

In some cases, however, these drugs may be unsuitable for patients with heart disease. If you are considering one of these drugs and you have heart disease, as many diabetics do, be sure to tell your doctor. In rare cases, the pills may create “priapism,” a prolonged and painful erection lasting six hours or more (although reversible with prompt medical attention).
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