The neurovascular mechanism of erection is complex and involves multiple factors including hormones, neurotransmitters, elements of the autonomic nervous system (sympathetic and parasympathetic) and vasodilators such as NO. The common causes of ED include psychogenic disturbance with failure to relax cavernous smooth muscle, arterial insufficiency as a result of atheromatous disease, damage to the parasympathetic nervous system, spinal cord injury, diabetes or following pelvic surgery such as radical prostatectomy, radical cystectomy or bowel resection . It is important to note that cavernous nerves are unique in that although they belong to the autonomic nerves system they do not release either acetylcholine (Ach) or norepinephrine; however, they release NO in the penis. NO relaxes the smooth muscle of the corpora cavernosa via cyclic GMP (cGMP), allowing expansion of the cavernosal lacunar spaces, blood flow and erection. Thus, NO is not a direct dilator of the smooth muscle of cavernosal bodies, but it is an important mediator in this process. Erectile function may also be adversely affected by cigarette smoking, excess alcohol consumption, obesity and systemic diseases such as mononucleosis, hepatitis, HIV and cancer. Some men are prone to develop an erection that fails to subside after ejaculation (ie, priapism). The condition is associated with sickle-cell disease and leukemia, or may be a result of intracavernosal injection of drugs such as prostaglandin E1 . Peyronie’s disease causes a physical bend in the erect penis and also contributes to ED.
Erectile dysfunction supplements and other natural remedies have long been used in Chinese, African and other cultures. But unlike prescription medications for erectile dysfunction, such as sildenafil (Viagra), vardenafil (Levitra, Staxyn), tadalafil (Cialis, Adcirca) and avanafil (Stendra), erectile dysfunction herbs and supplements haven't been well-studied or tested. Some can cause side effects or interact with other medications. And the amount of the active ingredient can vary greatly from product to product.