Erectile dysfunction (ED) is “the inability to achieve or sustain an erection that is sufficient for satisfactory sexual performance.”[1] The prevalence of ED among adult males aged 40–79 has been estimated to be between 30% and 50%.[2][3]
Sexual stimulation normally causes the release of nitric oxide (NO) and acetylcholine (ACh) from nerve fibers in the penis, initiating a molecular signaling cascade that ultimately results in the relaxation of penile smooth muscle tissue, an elevation in blood flow, and tumescence (an erection). These processes are disrupted in ED. ED can be categorized as psychogenic ED or organic ED; the latter can be broadly characterized as neurogenic ED, vasculogenic ED, or iatrogenic (medication- or surgery-induced) ED.[1]