A deficiency of L-arginine, however, does not generally disrupt nitric oxide synthesis because L-arginine availability is not the rate-limiting step in this process. In fact, research over the past five years has identified an endogenous (occurs in the body naturally) inhibitor called “asymmetric dimethylarginine” or ADMA, an amino acid which blocks the production of nitric oxide. By acting as an L-arginine mimic, this damaging look-alike effectively elbows out L-arginine and pushes it off to the side in the biochemical pathway leading to the synthesis of nitric oxide. ADMA is relatively elevated in patients with hypertension, high levels of cholesterol, triglycerides, homocysteine and low-density lipoprotein (LDL), and low levels of high-density lipoprotein (HDL), as well as with aging itself. This inhibitor of nitric oxide synthesis may very well be the common factor shared by all of these abnormal conditions. Increased levels of this detrimental inhibitor (ADMA) block nitric oxide production, leading to endothelial dysfunction.
The authors observe that multiple factors may be involved. In addition to decreased exercise capacity, patients with chronic heart failure have blood vessel and circulation abnormalities that can reduce blood flow into the penis and interfere with the ability to maintain an erection. And erectile dysfunction can be caused or worsened by many of the medications that are commonly prescribed to treat chronic heart failure.
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).
With atherosclerosis, the blood vessels are not able to dilate properly, which is called endothelial dysfunction (see the Figure). Cholesterol builds up in the blood vessel walls and forms plaques, which make the vessels narrow and slow down blood flow. When a plaque becomes very advanced, it can completely stop blood from passing through, which is what happens in a heart attack. Atherosclerosis affects not only the blood vessels supplying the heart (coronary arteries), but also blood vessels throughout the entire body. Atherosclerosis causes angina (chest pain that is often exertional), heart attacks, strokes, claudication (pain in the legs with walking), and ED. Atherosclerosis affects different people in different places, but it often affects the penis first, then the heart and brain, and the legs last. Because the first stage of atherosclerosis, endothelial dysfunction, usually affects the penis first, ED can be a warning sign that a heart attack or a stroke may follow, often in the next 3 to 5 years. This warning sign can be a good thing if it alerts you and your doctor that you have atherosclerosis, because then you can take steps to treat the atherosclerosis and prevent a heart attack or stroke.
Diabetes mellitus is associated with both decreased erectile function and increased cardiovascular risk. The MMAS found that the age-adjusted probability of complete impotence was 3 times higher in patients with diabetes mellitus than in those without the disease.6x6Kloner, RA. Erectile dysfunction and cardiovascular risk factors. Hosp Pract (Off Ed). 2001; 36: 41–44 (49-51.)

Unlike intraurethral suppositories, intracavernosal injection (IC) injection of vasoactive agents such as PGE-1 has consistently been shown to be effective in the treatment of ED in men with diabetes. In a study of 336 men with diabetes-related ED, 83% of patients reported erections satisfactory for intercourse after IC injection of PGE-1.55 Unfortunately, 24% of these patients also reported penile pain, one of the most common side effects of IC injection therapy. Other studies have noted similar effectiveness rates.56,57


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The EDDM patient has a variety of firstline options. The risk factors for vascular disease are the risk factors for ED. First-line therapy begins with attempts to minimize or eliminate these factors. These include smoking cessation, regular exercise, tighter glycemic control by attention to dietary restrictions, addition of statin drugs to correct dyslipidemia, and moderation of alcohol ingestion. Although there is very limited evidence that these modifications will dramatically reverse ED, they certainly will sponsor improved general health.4

Abstract | Full Text | Full Text PDF | PubMed | Scopus (30) | Google ScholarSee all References Erections result from relaxation of the corpora cavernosa, which is mediated either by increasing intracellular cyclic guanosine monophosphate (cGMP) or cyclic adenosine monophosphate or by inhibition of their degradation. Increased parasympathetic tone results in a decrease in norepinephrine release and an increase in the release of acetylcholine; subsequently, NO synthase activity increases, which releases NO from both endothelial cells and nonadrenergic, noncholinergic neurons.10x10Kloner, RA and Zusman, RM. Cardiovascular effects of sildenafil citrate and recommendations for its use. Am J Cardiol. 1999; 84: 11N–17N


Abstract | Full Text | Full Text PDF | PubMed | Scopus (95) | Google ScholarSee all References Phosphodiesterase type 5 is found predominantly in the smooth muscle of the corpora cavernosa but can be found in smaller quantities in platelets and other vascular smooth muscle.56x56Wallis, RM, Corbin, JD, Francis, SH, and Ellis, P. Tissue distribution of phosphodiesterase families and the effects of sildenafil on tissue cyclic nucleotides, platelet function, and the contractile responses of trabeculae carneae and aortic rings in vitro. Am J Cardiol. 1999; 83: 3C–12C

airdone/ShutterstockErectile dysfunction (ED) is a serious issue for men, which helps explain all the prescription drugs, over-the-counter treatments, and herbal concoctions that claim to cure ED. (In fact, it’s one of the top nine health risks men need to watch out for.) But before any guy decides to take matters into his own hands, he should talk to his doctor about a heart checkup: A new study published in the journal Vascular Medicine suggests ED can signal cardiovascular concerns.

Erectile dysfunction is defined as the inability to attain or maintain a penile erection sufficient for satisfactory sexual performance. Cases of ED may be classified as predominantly organic in nature, predominantly psychogenic, or mixed. Usual organic aetiologies are vasculogenic, hormonal, and neurogenic. Owing to the relationship of vasculogenic ED with CVD, it is important to distinguish men with predominantly vasculogenic ED from those with predominantly psychogenic ED or non-vasculogenic organic ED.

Second-generation cardioselective beta-blockers (atenolol, metoprolol, bisoprolol, etc.) can also lead to ED. Atenolol was shown to cause significant reduction of sexual activity compared with placebo in a double-blind, parallel-arm study.22 The same study also showed a significant reduction in testosterone levels with atenolol versus valsartan. An open, prospective study of hypertensive men treated with atenolol, metoprolol and bisoprolol for at least 6 months showed high prevalence of ED – approaching 66 % – in these patients.23
Abstract | Full Text | Full Text PDF | PubMed | Scopus (53) | Google ScholarSee all References Erectile dysfunction is a common physiological disorder. According to estimates from the National Institutes of Health, ED affects 10 million to 20 million men in the United States; another 10 million men are affected by partial ED, defined as present but diminished erectile function.2x2NIH Consensus Development Panel on Impotence. NIH Consensus Conference: impotence. JAMA. 1993; 270: 83–90
But recently Brandon had some troubles keeping it up. At first, Kayla just thought it was her and that he needed some kind of a change to what they usually did, but later Brandon admitted that as of late, he just couldn’t seem to maintain an erection, and that it took way too much effort to go long. It wasn’t that he wasn’t aroused; his body just wasn’t keeping up.
“If a diabetic patient has erectile dysfunction, it’s not enough to provide Viagra [sildenafil] or Cialis [tadalafil] and then send him on his merry way,” J. Francois Eid, MD, a New York City urologist, said at the annual meeting of the American Association of Diabetes Educators. “It’s important to let individuals know the drug has not cured the erectile dysfunction. If patients don’t take care of the diabetes, the erectile dysfunction progresses.”
A number of drugs are known to cause ED in patients with DM (Table 1). For example, many EDDM patients are on antihypertensive medications. Replacement of thiazides or beta-blockers with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers may be sufficient to regain erectile ability.5 Furthermore, discontinuation of selective serotonin reuptake inhibitors, if these drugs are not essential for patient well-being, may be therapeutic. Careful monitoring following drug discontinuation will help to determine if ED is due to the medication or other underlying disorders. The benefits of continued drug therapy with these drugs should always be weighed against the likelihood of causing ED and impacting on the patient's QOL.
At the same time, people with diabetes are susceptible to a type of blood vessel damage known as endothelial dysfunction. A recent study found that men with ED are at a greater risk of heart disease, which is also associated with endothelial dysfunction. If blood vessels aren't in good working order, the penis may not get enough blood for an erection.
For oral erectile dysfunction medicines to work as desired, they must be used properly in the first place. This means taking the medicine 30–45 minutes before engaging in sexual intimacy; taking the drug on an empty stomach or at least avoiding a heavy or high-fat meal before taking the drug (this is especially important when using sildenafil); and engaging in adequate genital stimulation before attempting intercourse. Drinking small amounts of alcohol (one to two drinks) should not compromise the effectiveness of erectile dysfunction medicines, but larger amounts of alcohol can diminish a man’s ability to have an erection.
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