# What causes ED

> The conditions behind the symptom — and why finding the cause matters more than treating it.

- **Source:** ED Treatment Guides (https://www.edtreatmentguides.com/causes)
- **Causes covered:** 15

| Cause | Category | Mechanism |
| --- | --- | --- |
| [Heart disease](https://www.edtreatmentguides.com/causes/cardiovascular-disease) | Vascular | The same endothelial damage that narrows coronary arteries narrows the smaller penile arteries first. |
| [Diabetes](https://www.edtreatmentguides.com/causes/diabetes) | Metabolic | High glucose damages both the small blood vessels and the autonomic nerves that trigger an erection, and lowers testosterone alongside. |
| [Low testosterone](https://www.edtreatmentguides.com/causes/low-testosterone) | Hormonal | Testosterone maintains libido and supports the nitric oxide machinery in erectile tissue; deficiency reduces desire more than it reduces blood flow. |
| [Obesity](https://www.edtreatmentguides.com/causes/obesity) | Metabolic | Adipose tissue converts testosterone to oestrogen, drives inflammation and insulin resistance, and impairs the endothelium. |
| [Sleep apnoea](https://www.edtreatmentguides.com/causes/sleep-apnea) | Metabolic | Repeated overnight oxygen dips damage the endothelium and disrupt the nocturnal testosterone surge. |
| [Smoking & alcohol](https://www.edtreatmentguides.com/causes/smoking-and-alcohol) | Lifestyle | Nicotine and combustion products damage the endothelium; alcohol and other drugs act on nerves, hormones and central arousal pathways. |
| [Performance anxiety](https://www.edtreatmentguides.com/causes/performance-anxiety) | Psychological | Anxiety activates the sympathetic nervous system, which constricts penile arteries — the exact opposite of what an erection requires. |
| [Depression & stress](https://www.edtreatmentguides.com/causes/depression-and-stress) | Psychological | Depression reduces central sexual drive and dopaminergic signalling; chronic stress raises cortisol and sympathetic tone. |
| [Medication](https://www.edtreatmentguides.com/causes/medication-side-effects) | Medication-related | Different drug classes interfere at different points — blood pressure, hormones, nerve signalling, or central arousal. |
| [Prostate treatment](https://www.edtreatmentguides.com/causes/prostate-treatment) | Structural & surgical | Surgery and radiation injure the cavernous nerves running alongside the prostate; hormone therapy removes the testosterone that drives desire. |
| [Peyronie's disease](https://www.edtreatmentguides.com/causes/peyronies-disease) | Structural & surgical | Fibrous plaque forms in the tunica albuginea, preventing that part of the penis from expanding evenly during erection. |
| [Ageing](https://www.edtreatmentguides.com/causes/ageing) | Vascular | Age brings slower arousal and reduced tissue elasticity, but the substantial change is the accumulation of vascular, metabolic and hormonal conditions. |
| [Neurological conditions](https://www.edtreatmentguides.com/causes/neurological-conditions) | Neurological | Damage anywhere along the pathway from brain to spinal cord to pelvic nerves interrupts the signal that starts an erection. |
| [Kidney & liver disease](https://www.edtreatmentguides.com/causes/kidney-and-liver-disease) | Metabolic | Organ failure disrupts hormone balance, damages blood vessels and nerves, and brings a medication list that adds further problems. |
| [Thyroid & prolactin](https://www.edtreatmentguides.com/causes/thyroid-and-prolactin) | Hormonal | Thyroid hormone sets the metabolic rate of every tissue; prolactin suppresses the hormonal axis that produces testosterone. |

## Every cause page

- [ED and Heart Disease: Why This Symptom Is a Warning](https://www.edtreatmentguides.com/causes/cardiovascular-disease) — Erectile dysfunction frequently appears three to five years before a heart attack or stroke. It is the same disease process, showing up first in a smaller artery. This is the most important page on this site.
- [Diabetes and ED: Why It Happens Earlier and Hits Harder](https://www.edtreatmentguides.com/causes/diabetes) — Around half of men with diabetes develop erectile dysfunction, often a decade or more earlier than other men. The damage is to nerves and small vessels together, which is why treatment needs a different approach.
- [Low Testosterone and ED: Sorting Signal From Marketing](https://www.edtreatmentguides.com/causes/low-testosterone) — Low testosterone is a real, treatable condition — and also the most oversold explanation for erectile dysfunction on the internet. Here is how to tell whether it applies to you.
- [Obesity, Metabolic Syndrome and ED](https://www.edtreatmentguides.com/causes/obesity) — Excess weight causes erectile dysfunction through at least four separate mechanisms working at once — which is also why weight loss is one of the few interventions that improves several of them together.
- [Sleep Apnoea, Poor Sleep and ED](https://www.edtreatmentguides.com/causes/sleep-apnea) — Obstructive sleep apnoea is one of the most commonly missed contributors to erectile dysfunction. It suppresses testosterone, damages blood vessels, and is entirely treatable.
- [Smoking, Alcohol, Cannabis and ED](https://www.edtreatmentguides.com/causes/smoking-and-alcohol) — Smoking roughly doubles the risk of erectile dysfunction, and the damage is at least partly reversible. Alcohol's effects are more nuanced — but heavy drinking is unambiguous.
- [Performance Anxiety: The Self-Reinforcing Cause of ED](https://www.edtreatmentguides.com/causes/performance-anxiety) — Anxiety about erections is the most common cause of erectile dysfunction in men under 40, and it becomes a second problem layered on top of every other cause. It is also one of the most treatable.
- [Depression, Stress and ED: A Two-Way Street](https://www.edtreatmentguides.com/causes/depression-and-stress) — Depression causes erectile dysfunction, erectile dysfunction causes depression, and the antidepressants that treat one frequently worsen the other. Untangling that requires treating both deliberately.
- [Medications That Cause ED — and What to Do About It](https://www.edtreatmentguides.com/causes/medication-side-effects) — Drug-induced erectile dysfunction is common, frequently missed, and often fixable by changing to an alternative in the same class. It is also the reason you should never stop a medication on your own.
- [ED After Prostate Surgery, Radiotherapy and Hormone Therapy](https://www.edtreatmentguides.com/causes/prostate-treatment) — Erectile dysfunction after prostate cancer treatment is common, expected, and takes a different treatment approach. Recovery is measured in years, not weeks — and starting early matters.
- [Peyronie's Disease: Curvature, Pain and ED](https://www.edtreatmentguides.com/causes/peyronies-disease) — Peyronie's disease causes scar tissue in the penis, leading to curvature, pain and often erectile dysfunction. It is more common than most men realise, and there is a specific window when treatment works best.
- [Is ED Just a Normal Part of Getting Older?](https://www.edtreatmentguides.com/causes/ageing) — Erectile dysfunction becomes more common with every decade — but age itself is not the mechanism. What accumulates with age is the conditions that cause it, and most of those are treatable.
- [Neurological Causes of ED: MS, Parkinson's, Spinal Injury and Stroke](https://www.edtreatmentguides.com/causes/neurological-conditions) — An erection is a nerve signal before it is a blood-flow event. When the signal is interrupted anywhere along its path, tablets that amplify it have much less to work with — which changes what treatment makes sense.
- [Chronic Kidney and Liver Disease as Causes of ED](https://www.edtreatmentguides.com/causes/kidney-and-liver-disease) — Erectile dysfunction affects the majority of men on dialysis and is very common in cirrhosis. Both conditions attack the problem from several directions at once — hormonal, vascular and pharmacological.
- [Thyroid Disorders and High Prolactin: The Blood Tests People Skip](https://www.edtreatmentguides.com/causes/thyroid-and-prolactin) — Two straightforward blood tests, two genuinely reversible causes of erectile dysfunction — and both are routinely left off the workup because nobody thought to ask for them.

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_This page is general health information, not medical advice. It cannot account for your own history, medications or risk factors. Talk to a licensed clinician before starting, stopping or changing any treatment._

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