These drugs facilitate erection by inhibiting the PDE5 enzyme, by blocking the degradation of cyclic guanosine monophosphate (cGMP) in the cavernous smooth muscles. This inhibition results in the prolonged activity of cGMP, which further decreases intracellular calcium concentrations, maintains smooth muscle relaxation and, hence, results in rigid penile erections.
The development of PDE5-inhibitors is a clear example of how Western medicine approached the problem of ED differently from Eastern medicine. The erectogenic effect of sildenafil (Viagra®) was discovered by accident when patients undergoing heart clinical trials reported better erections as a side effect after taking sildenafil. This observation led to further elucidation of the NO/cGMP signalling pathway and development of PDE5-inhibitors as a first-line therapy in ED (5).
Enlargement of the prostate gland, another condition that occurs with increasing frequency in men as they age, can also cause ED. In a 2012 Swiss study, 82 men with moderate to severe symptoms of prostate enlargement, who were also experiencing problems such as ED or loss of libido, took 320 mg of saw palmetto extract daily for 8 weeks. At the end of the study, the men’s ‘International Prostate Symptom Score’ (IPSS), a method of measuring prostate health based on a questionnaire, was reduced by an average of 51 percent. In addition, their ED, libido, and other sexual functions had also improved by an average of over 40 percent. Unlike the drug approaches used in conventional medicine, which can even cause ED as a side effect, saw palmetto is very effective in treating prostate problems and is free from side effects.
Diseases like diabetes, cardiovascular disease, atherosclerosis, kidney disease, obesity, multiple sclerosis, and depression, and activities like bicycling, smoking, alcohol or drug abuse can impair blood flow or nerve impulses throughout the body. Surgery, as well as certain medications, can also result in ED. However, this may be a temporary problem.4
If the condition is not treated immediately, it can lead to scarring and permanent erectile dysfunction. Long lasting erections may associated with pain due to the lack of oxygen to the penis because the penis is filled with oxygen deplete venous blood. Peyronie’s disease (a scarring of some of the deep tissues in the penis) can have a localized area of pain but usually involves a lump and some deviation of the erection to the affected side.
Poor sleep patterns can be a contributing factor for erectile dysfunction, Mucher says. One review published in the journal Brain Research emphasized the intricate relationship between the level of sex hormones like testosterone, sexual function, and sleep, noting that testosterone levels increase with improved sleep, and lower levels are associated with sexual dysfunction. Hormone secretion is controlled by the body’s internal clock, and sleep patterns likely help the body determine when to release certain hormones. 
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