Erectile dysfunction: what causes it

Erectile dysfunction (ED) means difficulty getting or keeping an erection firm enough for sex, often enough to be a problem for you. It is one of the most common things we see, and one of the least talked about. By the age of 40 to 70, around half of men have some degree of it. There is no judgement here and no assumptions: ED is a medical issue with medical causes, and for most men it is straightforward to treat once you understand what is driving it.

This article explains what actually causes ED, why the cause matters for treatment, and how an assessment teases the different threads apart.

How an erection actually works

An erection is a blood-flow event. When you are aroused, nerves release a chemical messenger called nitric oxide. That relaxes the smooth muscle in the walls of the arteries supplying the penis, blood flows in, and the tissue expands and traps it. An enzyme called PDE5 later breaks the signal down and the erection subsides.

Two things follow from this. First, anything that narrows or stiffens blood vessels can cause ED. Second, the most common ED medications work by blocking PDE5, which keeps the relaxing signal going for longer. That is why they are called PDE5 inhibitors.

The physical causes

Most ED in men over 40 has a physical (organic) component, and vascular causes lead the list.

Vascular: furred or narrowed arteries reduce blood flow. The vessels in the penis are narrower than those in the heart, so they often show trouble first. This is why ED can be an early warning of wider cardiovascular disease.

Diabetes: high blood sugar damages both the small blood vessels and the nerves that trigger an erection. ED is common in men with type 2 diabetes, sometimes before the diabetes itself has been picked up.

Hormonal: low testosterone can reduce desire and the quality of erections. It tends to cause a gradual loss of morning erections and lower libido alongside the ED.

Neurological: conditions such as multiple sclerosis, spinal injury, or nerve damage after pelvic surgery (for example prostate surgery) interrupt the signal.

After treatment for prostate or pelvic cancer: surgery and radiotherapy can affect the nerves and vessels involved.

The medication causes

Some prescribed medicines cause or worsen ED as a side effect. The common culprits are:

Blood pressure medication: particularly beta-blockers and thiazide diuretics.

Antidepressants: especially the SSRI group.

Finasteride: used for hair loss and prostate enlargement.

ome antipsychotics and long-term opioid painkillers.

If your ED started soon after a new medicine, that is worth flagging. Do not stop a prescribed medication on your own; there are often alternatives, and the assessment can help you weigh them up with the doctor who prescribed it.

The psychological causes

The mind matters too. Performance anxiety, stress, low mood, depression, and relationship strain can all cause ED, and they frequently sit alongside a physical cause rather than instead of one.

One useful clue: if you still get firm morning or night-time erections, or erections in some situations but not others, that points towards a psychological component. If erections have faded across the board, a physical cause is more likely. In practice, mixed pictures are the most common of all.

Lifestyle factors that tip the balance

Smoking, heavy drinking, carrying extra weight, inactivity, and poor sleep (including untreated sleep apnoea) all worsen ED, mostly by harming blood vessels and lowering testosterone. The encouraging side of this is that the same changes that help your erections also protect your heart, so the effort is rarely wasted.

How we work out which it is

Your assessment starts with a short questionnaire called the IIEF-5, a five-item score that gives a baseline of how severe the ED is. The doctor then asks about onset (sudden or gradual), morning erections, whether it happens in all situations, your mood and relationships, and your general health and medications.

Because ED can be a vascular warning sign, the assessment also looks at cardiovascular risk, and where it is useful the doctor may suggest blood tests for testosterone, blood sugar (HbA1c), cholesterol, and thyroid function. The aim is to treat the right thing, not just hand over a tablet.

When ED needs more than a prescription

Most men can be treated safely and simply. A few situations need a closer look first, and the assessment is partly there to catch them. Sudden ED in a younger man with no risk factors, ED with new back pain or numbness, or ED alongside chest pain on exertion all deserve proper evaluation before treatment. Where something points to an underlying problem, we investigate or refer rather than paper over it.

If you would rather begin with your own NHS GP, that is a reasonable route and we will say so. ED care is also available on the NHS.

Begin your assessment at this link. Online or in person at Westfield London.

Ready to start?

If you want to move from reading to acting, the next step is a short, confidential assessment with one of our doctors. No judgement, no assumptions.

Begin your assessment at this link. Online or in person at Westfield London.