Erectile Dysfunction (Impotence)

What is erectile dysfunction?
Erectile dysfunction (ED) means that you cannot get and/or maintain an erection. In some cases the penis becomes partly erect, but not hard enough to have sex properly. In some cases, there is no swelling or fullness of the penis at all. ED is sometimes called impotence.

How common is erectile dysfunction?
Most men have odd times when they cannot get an erection. For example, you may not get an erection so easily if you are tired, stressed, distracted, or have drunk too much alcohol. For most men it is only temporary, and an erection occurs most times when you are sexually aroused.

However, some men have persistent, or recurring, ED. It can occur at any age, but becomes more common with increasing age. About half of men between the age of 40 and 70 have ED. About 7 in 10 men aged 70 and above have ED.

How does an erection normally occur?
When you are sexually aroused, messages from your brain travel down nerves to your penis. Chemicals called 'neurotransmitters' are then released from the ends of the nerves in the penis. Stimulation of the penis can also cause local nerve endings to release neurotransmitter chemicals.

The neurotransmitters which are released in the penis cause another chemical to be made called cyclic guanosine monophosphate (cGMP). An increase of cGMP causes the arteries in the penis to dilate (widen). This allows extra blood to flood into the penis. The rapid inflow of blood causes the penis to swell into an erection. The swollen inner part of the penis also 'presses' on the veins nearer to the skin surface of the penis. These veins normally drain the penis of blood. So, the flow of blood out of the penis is also restricted, which enhances the erection.

The cGMP is soon converted into another inactive chemical. But, as you remain sexually aroused whilst having sex, your brain keeps sending nerve messages to the penis which makes more cGMP to maintain the erection. When the level of cGMP falls, the blood flow to the penis returns to normal, and the penis gradually returns to the non-erect state.

What causes erectile dysfunction?
There are several causes which tend to be grouped into 'physical' and 'psychological'.

Physical causes
About 8 in 10 cases of ED are due to a physical cause. If the ED is due to a physical cause, you are likely to still have a normal sex drive (libido). Causes include:

Reduced blood flow to the penis. Like in other parts of the body, the arteries which take blood to the penis can become narrowed. The blood flow may then not be enough to cause an erection. 'Risk factors' can increase your chance of 'narrowing of the arteries'. These include: getting older; high blood pressure; high cholesterol; smoking; diabetes.
Diseases which affect the nerves going to the penis. For example, multiple sclerosis, a stroke, etc.
Diabetes. This is one of the commonest causes of ED. Diabetes can affect blood vessels and nerves.
Injury to the nerves going to the penis. For example, spinal injury, following surgery to nearby structures, fractured pelvis, radiotherapy to the genital area, etc.
Side-effect of certain medicines. The most common are: some antidepressants; betablockers such as propranolol, atenolol etc; some diuretics ('water tablets'); cimetidine. Many other less commonly used tablets sometimes cause ED.
Alcohol and drug abuse.
Cycling. ED after long distance cycling is thought to be common. It is probably due to pressure on the nerves going to the penis from sitting on the saddle for long periods. This may affect the function of the nerve after the ride.
Hormone causes are rare. For example, a lack of a hormone called testosterone which is made in the testes.
Excessive outflow of blood from the penis through the veins ('venous leak'). This is rare but can be caused by various conditions of the penis.
In most cases due to physical causes (apart from injury or after surgery) the ED tends to develop slowly. So, you may have intermittent or partial ED for a while, which may gradually get worse. In some cases, ED causes poor self esteem, anxiety, and even depression. These reactions to ED can make the problem worse.

Mental heath ('psychological') causes
Various mental health conditions may cause you to develop ED. For example:

Stress. For example, due to a difficult work or home situation.
Relationship difficulties.
Typically, the ED develops quite suddenly if it is a symptom of a mental health problem. The ED may resolve when your mental state improves. For example, if your anxiety or depression eases. However, some people become even more anxious or depressed when they develop ED. They do not realise it is a reaction to their mental health problem. This can make matters worse and lead to a 'vicious circle' of worsening anxiety and persisting ED.

As a rule, a psychological cause is more likely for the ED than a physical cause if there are times when you can get a good erection, even though most of the time you cannot. (For example, if you can get an erection by masturbating, or wake up in the morning with an erection.)

Erectile dysfunction, heart disease and other vascular diseases
Although ED can be caused by various conditions, about 7 in 10 cases are due to narrowing of the small arteries in the penis. This causes reduced blood flow to the penis. This is the same problem that can occur in other blood vessels. For example, narrowing of the blood vessels in the heart (the coronary arteries) is a cause of angina and other heart problems. Narrowing of blood vessels to the brain is a risk factor for having a stroke. Narrowing of blood vessels in the legs can cause peripheral vascular disease.

The root cause of the narrowing of the arteries is caused by atheroma. Atheroma is like fatty patches or 'plaques' that develop within the inside lining of arteries. (This is similar to water pipes that get 'furred up' with scale.) Plaques of atheroma may gradually form over a number of years in one or more places in the body, commonly in arteries going to the heart, brain, legs and penis. In time, these can become bigger and cause enough narrowing of one or more of the arteries to cause symptoms and problems.

Certain 'risk factors' increase the risk of more atheroma forming which can make atheroma-related conditions worse. These are discussed in more detail in another leaflet called 'Preventing Cardiovascular Disease'. Briefly, risk factors that can be modified and may help to prevent atheroma-related conditions from getting worse are:

Smoking. Smoking is one of the biggest risk factors for developing heart disease. Smoking also roughly doubles your chance of developing ED. Young smokers may not be aware that they have a much greater risk of developing ED by middle age compared to non-smokers. If you smoke, you should make every effort to stop.
High blood pressure. Make sure your blood pressure is checked at least once a year. If it is high it can be treated.
If you are overweight, losing some weight is advised.
A high cholesterol. This can be treated if it is high.
Inactivity. We should all aim to do some moderate physical activity on most days of the week for at least 30 minutes. For example, brisk walking, swimming, cycling, dancing, gardening, etc.
Diet. You should aim to eat a healthy diet. Details in a leaflet called 'Healthy Eating'
Alcohol excess.
Diabetes. If you have diabetes, good control of the blood sugar level and blood pressure can help to minimise the impact of diabetes on the blood vessels.
Note: ED caused by narrowed arteries commonly develops several years before any symptoms or problems develop due to narrowing of the coronary arteries (or other arteries). Therefore, ED is thought of as an 'early warning signal' that heart disease (or other cardiovascular diseases) may develop. This is why some of the tests listed below may be advised if you develop ED. Also, you are likely to be advised by your doctor on how to modify any 'risk factors' listed above with the aim of preventing heart disease from developing.