Causes of erectile dysfunction

The mechanism by which a man achieves an erection is complex, commencing with some form of sensory stimulus and then involving both central and peripheral neural pathways that lead to vascular changes that in turn result in an erection. Interference with this process can occur at a number of levels, and accordingly there are a large number of different causes of erectile dysfunction.

Traditionally, organic causes of erectile dysfunction (ED) were separated from psychogenic causes, but we now recognise that such a separation is artificial, as both processes are present at the same time in most patients. Indeed, it is now recognised that for many men there are multiple pathophysiological factors, both physical and psychogenic, which contribute to the ED.

Causes of erectile dysfunction.

• Psychogenic
• Organic
• Neurological
• Vascular
• Endocrine
• ED of ageing
• Latrogenic

Psychogenic ED Psychogenic ED can occur in a variety of situations, and although the division into predisposing, precipitating and maintaining factors is often inappropriate, it does provide a framework upon which to identify the causes of psychogenic ED, where they exist.

Vascular ED
The single most common organic cause of ED is vascular disease or atherosclerosis. Just as atherosclerosis affects the myocardial or cerebral vasculature, risk factors for vasculogenic ED include hypertension, diabetes, hyperlipidaemia and smoking. All these factors, both individually and collectively (with the possible exception of smoking), have been associated with the development of ED, and we are increasingly recognising that early diagnosis of ED may help us to identify reversible cardiovascular risk factors that, if treated, might help to reduce serious cardiac morbidity in the future.

Diabetic ED
Men with diabetes are around three times more likely to develop ED than non-diabetics. The mechanisms underlying this include the autonomic neuropathy that commonly accompanies diabetes, the vascular disease that results from diabetes and, as we are increasingly recognising, the endothelial dysfunction that is associated with diabetes. Endothelial release of nitric oxide is crucial to normal erection and we now know

Common organic causes of ED.

• Vascular disease
• Atherosclerosis
• Diabetes mellitus
• Hypertension
• Hyperlipidaemia
• Neurological disease
• Multiple sclerosis
• Diabetes mellitus
• Depression
• Spinal cord injury
• Cauda equina lesion
• Parkinson’s disease
• Alzheimer’s disease
• Pelvic fracture injury
• Endocrine and metabolic disease
• Hypogonadism
• Hyperprolactinaemia
• Renal failure
• ED of ageing
• latrogenic ED
• Pelvic radiotherapy
• Radical pelvic surgery, e.g. radical prostatectomy, radical cystectomy
• Drugs

Hypertension and hyperlipidaemia

As well as being risk factors for atherosclerotic ED, both hypertension and hyperlipidaemia on their own can cause ED.
Predisposing causes Issues that predispose the man to develop psychogenic ED

Examples

• Traumatic sexual experience, e.g. humiliation by partner in previous relationship
• Lifestyle issues, e.g. increased stress from financial, marital or work issues
• Educational issues, e.g. unrealistic expectations about sexual intercourse
• Cultural issues, e.g. repressed or abnormal sexuality as a result of cultural, religious or parental attitudes

Precipitating causes

Issues that precipitate loss of normal erectile function

Examples

• Infidelity can result in ED with either partner
• Ageing results in changes in sexual function which may not be expected or recognised
• Educational issues can lead to unrealistic expectations about sexual function
• Loss of partner by divorce or death may precipitate ED with subsequent partners

Maintaining factors

Issues that tend to maintain ED when some other cause has precipitated it Predisposing causes

Examples

• Performance-related anxiety, where anxiety leads to increased sympathetic nervous tone and increased smooth muscle contraction in the penis
• Poor communication may not allow couples to discuss problems with sexual function
• Educational issues can result in perpetuation of so-called ‘sexual myths’
• Fear of intimacy may exacerbate psychosexual problems

present in 17% of untreated hypertensive men, rising to 25% in those on treatment. With respect to dyslipidaemia, it is raised low-density lipoprotein (LDL) that is the major pathogenic risk factor for the ED associated with hyperlipidaemia. Increased levels of HDL (high-density lipoprotein) appear to be relatively protective against ED.