Normal penile erection is controlled by two mechanisms: reflex erection and psychogenic erection. Reflex erection occurs by directly touching the shaft of the penis, while psychogenic erection occurs by erotic or emotional stimuli. ED is a condition where erection does not take place by either mechanism. ED can occur because of hormonal imbalance, neural disorders or lack of adequate blood supply to the penis.54 Lack of blood supply can be a result of impaired endothelial function associated with CAD.54

Crossref | PubMed | Google ScholarSee all References These hormonal findings were supported by a study of 1132 men aged 30 to 79 years that found an inverse relationship between blood pressure and serum testosterone levels.32x32Khaw, KT and Barrett-Connor, E. Blood pressure and endogenous testosterone in men: an inverse relationship. J Hypertens. 1988; 6: 329–332
A cold slice of watermelon can do more than just satisfy thirst and hunger during the warm summer months; it can help with bedroom satisfaction. Citrulline, the amino acid found in high concentrations of watermelon, is found to improve blood flow to the penis. A 2011 study revealed men who suffered from mild to moderate ED and took L-citrulline supplementation showed an improvement with their erectile function and were very satisfied. Natural watermelon juice, or “nature’s Viagra,” can also be easier on the stomach, since taking pills like Viagra can cause nausea and diarrhea.
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.
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
ED is generally associated with significant changes in established cardiovascular risk factors. Atherosclerosis is the main cause of ED development in both the general population and patients with diabetes. However, the prevalence of ED is greater in patients with diabetes than in the general population.8 ED has been shown to occur at rates as high as 50 % in patients with CAD.9 A meta-analysis of 12 prospective cohort studies has provided evidence that ED is a predictor of IHD associated with an increased risk of CVD, stroke and all-cause mortality.10
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.
Nonsustained erection with detumescence after penetration is most commonly caused by anxiety or the vascular steel syndrome. In the vascular steel syndrome, blood is diverted from the engorged corpora cavernosae to accommodate the oxygen requirements of the thrusting pelvis. Questions should be asked regarding the presence or absence of nocturnal or morning erections and the ability to masturbate. Complete loss of nocturnal erections and the ability to masturbate are signs of neurological or vascular disease. It is important to remember that sexual desire is not lost with ED—only the ability to act on those emotions.
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.
Abstract | Full Text | Full Text PDF | PubMed | Scopus (395) | Google ScholarSee all References Sildenafil has no effect on bleeding time or prothrombin time when used either alone or in patients taking aspirin or warfarin.61x61Nehra, A, Colreavy, F, Khandheria, BK, and Chandrasekaran, K. Sildenafil citrate, a selective phosphodiesterase type 5 inhibitor: urologic and cardiovascular implications. World J Urol. 2001; 19: 40–45
Consider this:  penicillin, the first successful antibiotic, was derived from molds that inhibit bacterial growth.  Scientists had to figure out why the molds slowed bacteria, and refine the active ingredients.  Using herbal supplements is somewhat like putting mold on a wound.  It might help, a little, but it’s certainly not going to help as much as using penicillin.

ED is a common complication of diabetes that affects patients' quality of life. While the etiology of this complication may be multifactorial in nature, it is clear that it usually has a strong organic component. Because men with diabetes value their erectile function highly, it is important that providers encourage them to maintain good glycemic, blood pressure, and lipid control to minimize their risk of developing this complication.

Abstract | Full Text | Full Text PDF | PubMed | Scopus (58) | Google ScholarSee all References Erectile dysfunction secondary to cardiovascular disease often responds well to the standard ED treatments developed over the past few decades. Penile prosthesis implantation was developed in the 1970s, followed by intracavernosal injections of vasoactive agents, including papaverine, phentolamine, and prostaglandin E1, introduced in the 1980s.11x11Nehra, A. Intracavernosal therapy: when oral agents fail. Curr Urol Rep. 2001; 2: 468–472
Abstract | PubMed | Scopus (136) | Google ScholarSee all References Another study evaluated 32 hypertensive men with ED and 78 normotensive men with ED with regard to age, body mass index, hormonal profile, penile arterial flow, risk factors for arterial disease, psychiatric disease, and neurologic disease measured by pudendal nerve conduction studies.30x30Jaffe, A, Chen, Y, Kisch, ES, Fischel, B, Alon, M, and Stern, N. Erectile dysfunction in hypertensive subjects: assessment of potential determinants. Hypertension. 1996; 28: 859–862
Abstract | Full Text | Full Text PDF | PubMed | Scopus (95) | Google ScholarSee all References In conclusion, sildenafil, when used alone, seems to produce minimal decreases in blood pressure level, which are well tolerated in healthy patients and in those with stable ischemic coronary disease.3x3Zusman, RM, Morales, A, Glasser, DB, and Osterloh, IH. Overall cardiovascular profile of sildenafil citrate. Am J Cardiol. 1999; 83: 35C–44C

To date, there are no studies directly comparing the effectiveness of these three agents among diabetic men with ED, so it is impossible to state that one agent is superior to another in terms of effectiveness in diabetic patients. However, there are an number of studies that compare the individual agents to placebo in diabetic men with ED. For example, Boulton et al.41 completed a 12-week double-blind, placebo-controlled randomized clinical trial of the effectiveness of sildenafil in 219 men with ED and type 2 diabetes. They found that sildenafil resulted in a significant improvement in the ability to both achieve and maintain an erection adequate for sexual intercourse in men with type 2 diabetes. In a similar study, Rendell et al.42 randomized 268 diabetic men with ED to receive either sildenafil in a dose-escalation manner or placebo. At the conclusion of the 12-week study, 56% of the patients in the sildenafil arm reported improved erections, compared to 10% in the placebo arm (P < 0.001). Additionally, 61% of patients in the diabetic arm reported at least one successful attempt at sexual intercourse in the final month of the study, compared to 22% in the control arm (P < 0.001). Similar randomized studies have documented the effectiveness of both tadalafil43 and vardenafil44 in the treatment of diabetes-related ED.
Montorsi P,  Ravagnani PM,  Galli S,  Rotatori F,  Veglia F,  Briganti A,  Salonia A,  Dehò F,  Rigatti P,  Montorsi F,  Fiorentini C. Association between erectile dysfunction and coronary artery disease. Role of coronary clinical presentation and extent of coronary vessels involvement: the COBRA trial, Eur Heart J , 2006, vol. 27 (pg. 2632-2639)https://doi.org/10.1093/eurheartj/ehl142
Surgery for erectile dysfunction is usually considered only after all other options have failed. The two surgical options include the insertion of a semi-rigid rod or the implantation of a three-piece inflatable prosthesis. Penile prosthesis implantation has low infection, complication, and malfunction rates. However, since placement of an implant requires permanent injury to the erectile tissue of the penis, implant treatment is considered irreversible.
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