Endothelium lines blood vessels all over the body. Nitric oxide plays a significant role in maintaining the integrity of the endothelium which is crucial for adequate blood flow. Endothelial dysfunction arises in smokers, second-hand smokers, individuals having high levels of bad cholesterol and blood sugar. When blood vessels get structurally altered, blood flow through them get compromised, this leads to a variety of diseases that affect the heart, lungs and even the penis.Hence endothelial dysfunctioning can affect blood vessels that supply the penis thereby making nitric oxide crucial for its proper functioning.