Physical erectile dysfunction: vascular damage and diabetes
Physical erectile dysfunction (ED, the persistent inability to get or keep an erection firm enough for intercourse) is most often vascular: damaged vessels reduce blood inflow to the penis.
Remember
The usual mechanism of physical erectile dysfunction is vascular: damaged penile vessels cannot maintain the high pressure inside the corpus cavernosum (the spongy erectile tissue) that an erection needs, and long-standing diabetes damages the small vessels in this way.
Erectile dysfunction (ED) is the persistent inability to get or keep an erection firm enough for intercourse. When a physical cause is present, the usual problem is vascular, meaning damage to the blood vessels that supply the penis.
A normal erection relies on the arteries widening, the smooth muscle relaxing and the veins being squeezed shut. Blood is then trapped in the corpora cavernosa (the two columns of spongy erectile tissue running along the penis), and high pressure builds up inside them. The parasympathetic nerves (the 'rest and digest' nerves) start this process.
When arterial inflow falls, that high pressure cannot be maintained. The most common vascular cause is atherosclerosis (a fatty build-up that narrows arteries), often driven by smoking, diabetes and damage to the vessel lining.
In diabetes, microvascular complications (damage to the smallest blood vessels caused by long-standing high blood glucose) limit the blood supply to the penis, and diabetes also injures the lining of the larger arteries. In a man whose diabetic ED is vascular in this way, the picture can be that he gets an erection but loses rigidity quickly, so he has difficulty sustaining it rather than starting it, while desire is intact. Diabetes can also damage nerves and affect hormones, so the underlying cause is often mixed, although vascular damage is the commonest route.
ED is very common in men with diabetes, and it can also be an early sign of vascular disease, so men with diabetes and ED deserve a review of their risk of vascular disease.
Key facts
- Usual mechanism
- damaged penile vessels cannot maintain high pressure in the corpus cavernosum.
- Common causes
- smoking, diabetes, hypertension and high cholesterol.
- Diabetes
- microvascular damage limits the blood supply to the penis.
- Pattern in vascular diabetic ED
- progressive difficulty maintaining rigidity with preserved desire.
- Prevalence
- ED is very common in men with diabetes, and the proportion affected rises with age.
- Wider risk
- ED can mark underlying vascular disease.
- Treatment link
- drugs such as sildenafil relax smooth muscle and increase arterial blood flow.
Exam traps
- High pressure in the corpus spongiosum, the erectile tissue that also fills with blood during an erection, is not what makes the penis rigid, because it is meant to stay at low pressure so the urethra remains open.
- Excess activity of the sympathetic nerves, which are involved in detumescence (the loss of an erection), is not the recognised way in which diabetes causes ED, because erection is driven by parasympathetic nerves.
- Parasympathetic overactivity would not stop an erection being sustained, because those nerves relax the smooth muscle and let blood in, so overactivity would favour an erection.
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