Diabetes and male sexual function (Part 2)
ED is often associated with microangiopathy; thus, the presence of retinopathy is usually a good predictor of ED. Age, duration of DM and the presence of other diabetic complications correlates more with its future development. Between the ages of 40 to 70 years, the prevalence of ED is 52% for the general population, whereas in age-matched diabetics, it is as high as 75%. For men younger than 40 years of age, the prevalence of ED is 7.8%, but for men older than 40 years of age, it increases to 63% for type 1 diabetics and 71.1% for type 2 diabetics. The use of alcohol or antihypertensive medication appears to increase the risk of ED in this population.
The pathophysiology of ED in diabetes is not well understood. Associated neuropathy or vasculopathy (microangiopathy and generalized vascular disease) is considered to be the most important factors in the pathophysiology of DM-induced ED.
Recently, attention has been increasingly directed toward understanding the role of vascular endothelium and its control of penile cavernous smooth muscle tone. The two corpus cavernosum, which are the erectile bodies of the penis, consist of multiple lacunar spaces surrounded by cavernous smooth muscle. These lacunar spaces are lined by the endothelium. During sexual activity, neurotransmitters (nitric oxide [NO] being the most important) are released from either the penile nerve ending or the endothelium that triggers a relaxation of both cavernosal arteries and smooth muscle. This increases penile blood flow, causes dilation of the lacunar space and, eventually, an erection. In DM, it has been shown that endothelium-dependent smooth muscle relaxation is impaired, although the exact mechanism is not known. Endothelial dysfunction (the small ed) then leads to erectile dysfunction (the big ED) through smooth muscle dysfunction in the microvascular tree of the penis.