What actually causes erectile dysfunction?

An erection is a circulatory event. Nerve signals tell the smooth muscle in the penis to relax, blood fills two columns of spongy tissue, and the pressure of that blood seals the veins that would otherwise drain it. Anything that interferes with the nerves, the arteries or the sealing mechanism can cause erectile dysfunction. That is why ED so often turns out to be a symptom of something broader rather than a condition in isolation.

The vascular causes, which are the most common

The arteries that supply the penis are roughly a third of the diameter of the coronary arteries. When atherosclerosis narrows blood vessels throughout the body, those smaller vessels show it first. This is the single most useful thing to understand about ED: it frequently precedes a cardiac event by three to five years.

• High blood pressure, which damages the lining of blood vessels over time
• High cholesterol and the plaque it deposits
• Smoking, which both narrows vessels and impairs the chemistry that relaxes them
• Diabetes, which damages small vessels and the nerves alongside them
• Obesity and metabolic syndrome

Medicines that contribute

A surprising number of commonly prescribed medicines list erectile dysfunction as a side effect. This does not mean you should stop taking them — stopping blood pressure medication unilaterally is far more dangerous than ED — but it does mean it is worth raising with whoever prescribes them, because there are often alternatives within the same class.

• Some blood pressure medicines, particularly thiazide diuretics and older beta-blockers
• SSRI antidepressants, where sexual side effects are common and dose-related
• Antipsychotics that raise prolactin
• Finasteride and related medicines for hair loss or prostate enlargement
• Opioid painkillers, which suppress testosterone over time

Hormonal causes

Low testosterone is a less common cause than people assume, and it tends to reduce desire rather than the mechanics of the erection itself. If your interest in sex has dropped alongside the erectile difficulty, and you are also tired and losing muscle, a morning testosterone test is reasonable. Thyroid disease, in either direction, can also be involved.

The psychological side, which is not separate

It is tempting to sort ED into 'physical' and 'psychological' boxes, but in practice almost every case has both. A man with mild vascular disease has one disappointing experience, becomes anxious about the next one, and the anxiety does more damage than the original narrowing. Performance anxiety is self-reinforcing in a way that few other symptoms are.

One useful clue: if you still get firm erections on waking or when masturbating, but not with a partner, the plumbing is working and the cause is more likely to be psychological. If erections have faded everywhere and gradually, a physical cause is more likely.

What to do with all this

Treat the underlying cause where there is one, because that is the only approach that changes the trajectory rather than managing the symptom. Medication can work alongside that rather than instead of it. And if your ED came on suddenly, or you get chest pain on exertion, see a doctor in person before you start anything.

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