Over the past decades, the medical perspective on the causes of erectile dysfunction (ED) has shifted. Doctors used to think that almost all cases of ED were related to psychological factors. Now doctors believe that up to 85% of ED cases are caused by medical or physical problems. Only around 15% cases of ED are due to psychological factors. Sometimes, ED is due to a combination of physical and psychological causes.
In general, psychologically-based ED is more likely to develop suddenly with complete, immediate loss of function. This problem may be present most of the time or only in certain situations. These men will often still have erections upon awakening.
ED from organic or medical causes occurs gradually over time and progressively becomes worse. ED is present with most or all sexual interactions and these men either lack an erection upon awakening, or have poor erections.
A number of medical conditions share a common problem with ED, such as the impaired ability of blood vessels to open and allow normal blood flow.
Heart Disease, Atherosclerosis, and High Blood Pressure
Heart disease, atherosclerosis, high blood pressure, and high cholesterol levels are major risk factors for ED. Peripheral artery disease (PAD), a form of atherosclerosis, is very common in men who have ED. In fact, erectile problems may be a warning sign of these conditions in men at risk for atherosclerosis. Men who experience ED due to vascular causes have a greater risk for angina, (chest pain due to low oxygen levels in the blood), heart attack, and stroke.
ED is also a very common problem in men with high blood pressure. Many of the drugs used to treat hypertension (diuretics, calcium channel blockers, and beta-blockers) may also cause ED.
Diabetes is a major risk factor for ED. Damage to blood vessels and nerves is a common complication of diabetes. When the blood vessels or nerves of the penis are involved, ED can result. Diabetes is also associated with heart disease and chronic kidney disease, which are other risk factors for ED.
Obesity increases the risk for diabetes, heart disease, and ED.
Metabolic syndrome is a risk factor for ED in men older than age 50 years. It is a cluster of conditions that includes obesity and abdominal fat, unhealthy cholesterol and triglyceride levels, high blood pressure, and insulin resistance.
Benign Prostatic Hyperplasia
There appears to be a relationship between ED and the lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH or "enlarged prostate"). Men who have one condition often have the other. Both conditions share common risk factors including older age, high blood pressure, and diabetes. In addition, surgical and drug treatments for BPH can increase the risk for ED.
Neurologic diseases, such as Parkinson disease, multiple sclerosis, and stroke, can cause ED.
Endocrinologic and Hormonal Conditions
Endocrinologic conditions include diseases or conditions that involve abnormalities of the glands and hormonal imbalance. Hypogonadism, known informally as "low T," is a medical condition that results from low levels of the male hormone testosterone (androgen deficiency). Symptoms of hypogonadism can include reduced sexual desire (low libido) and ED.
However, low testosterone as the sole cause of ED likely affects only a small percentage of men. Hypogonadism is also associated with very small or shrinking testicles, loss of muscle mass, increased body fat, reduced bone density, fatigue, anemia, and declining sperm production. Many men with hypogonadism are infertile.
Hypogonadism is classified as either primary or secondary. Primary hypogonadism is caused by diseases or defects in the testicles that affect the production of testosterone. Secondary hypogonadism is due to problems in the hypothalamus or pituitary gland that cause high levels of the hormone prolactin. Hypothalamus and pituitary abnormalities also cause low levels of other hormones such as follicle-stimulating hormone and luteinizing hormone. These hormonal imbalances can result in low libido and ED.
Other hormonal and endocrinologic causes of ED include thyroid and adrenal gland problems.
Physical Trauma and Injury
Spinal cord injury and pelvic trauma, such as a pelvic fracture, can cause nerve damage that result in ED. Other conditions that can injure the spine and cause ED include spinal cord tumors, spina bifida, and a history of polio.
Certain types of surgery and radiation treatments can increase the risk for erectile dysfunction:
- Surgery for Prostate Diseases. Radical prostatectomy for prostate cancer is a common cause of ED. Nerve-sparing techniques can help reduce the loss of sexual function. Radiation treatments for prostate cancer also cause ED. Some surgical treatments for benign prostatic hyperplasia (BPH) can also cause ED, but this complication is relatively uncommon.
- Surgery for Colon and Rectal Cancers. Surgical and radiation treatments for colorectal cancers may cause ED.
- Fistula Surgery. Surgery to repair anal fistulas can affect the muscles that control the rectum (external anal sphincter muscles), sometimes causing ED. (Repair of these muscles may restore erectile function.)
- Orthopedic Surgery. ED can sometimes result from orthopedic surgery that affects pelvic nerves.
Note: Vasectomy does NOT cause ED.
ED can be a side effect of certain medications. They include:
- High blood pressure medications, particularly diuretics, beta-blockers, and calcium-channel blockers.
- Heart or cholesterol medications, such as digoxin, gemfibrozil, or clofibrate.
- Finasteride (Proscar) and dutasteride (Avodart), which are used to treat BPH. A lower-dose form of finasteride (Propecia), which is used to treat male pattern baldness, may also cause ED. ED may persist even after these medications are stopped.
- Medications used to treat depression and bipolar disorder, such as selective serotonin-reuptake inhibitors (SSRIs), tricyclic antidepressants, monoamine oxidase inhibitors, and lithium. Certain types of antipsychotic medication, such as phenothiazines (like compazine) and butyrophenones (like haloperidol), can also cause ED.
- Gastroesophageal reflux disorder (GERD) medications, used to reduce stomach acid, such as ranitidine (Zantac) and cimetidine (Tagamet).
- Hormone drugs, such as estrogens, corticosteroids, and 5-alpha reductase inhibitors.
- Chemotherapy drugs, such as methotrexate.
- Morphine and opioid drugs.
Anxiety has both emotional and physical consequences that can affect erectile function. It is among the most frequently cited contributors to psychological ED.
Stress, whether caused by major life events, daily hassles, or health problems, can affect sexual function. Post-traumatic stress disorder (PTSD), a mental condition caused by exposure to traumatic events, is strongly associated with ED.
Depression can reduce sexual desire and is associated with ED.
Troubles in relationships often have a direct impact on sexual function.