Erectile dysfunction in the ageing man.

Most studies have shown an increase in the prevalence of erectile dysfunction with ageing. Penile erection is a vascular phenomenon resulting from smooth muscle relaxation, arterial dilatation and venous restriction. The atherosclerosis of the penis that occurs with ageing causes a decrease in penile oxygen tension. This change in oxygen tension impacts directly upon both the physiologic function and the trabecular structure of the corpora cavernosa. Chronic ischaemia of the penis is associated with fibrosis of smooth muscle fibres and with endothelial and neuronal NO/cGMP pathways. The effects of androgens on libido and sexual behaviour are well established but their role in the erectile mechanism remains unclear. The histologic and haemodynamic causes responsible for the erectile decline in the ageing man are reviewed.