Erectile Dysfunction (ED): A Clinical Guide for Providers

Written by Empire Medical Training Editorial Team

Medically reviewed by Betsy Greenleaf, DO Board-Certified OB/GYN & Urogynecologist; Empire Director of Anti-Aging

Updated June 2026 ·11 min read

Erectile dysfunction (ED) is the consistent difficulty achieving or maintaining an erection adequate for satisfactory sexual activity. It is the most common male sexual dysfunction by a wide margin, affecting over 50% of men between the ages of 40 and 70, with prevalence rising steadily with age. Yet the most important clinical fact about ED is also the most often missed: it is rarely a stand-alone problem. As Dr. Betsy Greenleaf frames it in Empire's sexual dysfunction training, ED is usually a symptom — you have to look for “the roots under the leaves of the trees,” because the dysfunction in the bedroom is frequently the first visible sign of a vascular, metabolic, hormonal, or neurological problem elsewhere in the body.

This guide is part of Empire's broader sexual health resource center and is written for clinicians who want an accurate, practical overview. It is clinical education, not medical advice, and nothing here should be read as a treatment protocol or substitute for current evidence-based guidelines and individualized clinical judgment.

What is erectile dysfunction?

An erection is a vascular event. Erectile dysfunction is what happens when the chain of signals and blood flow that produces and sustains that event breaks down somewhere along its length. Clinically, ED is defined as the consistent difficulty getting or keeping an erection firm enough for sexual activity, often accompanied by reduced sexual desire and distress. The key word is consistent: an occasional off night is physiologically normal, whereas a persistent pattern is what defines the condition.

The single most useful reframe a clinician can offer is that ED is a symptom, not a diagnosis. Because a normal erection requires healthy arteries, intact nerves, adequate hormones, and a relaxed, stimulated brain all working in concert, a failure of erection points to a failure somewhere in that system. That is why Dr. Greenleaf urges providers to treat ED as a window into the whole patient rather than a localized complaint — and why it so often serves as an early, treatable warning of disease the patient does not yet know he has.

The physiology of an erection

Understanding ED begins with understanding how a normal erection is produced, because every treatment and nearly every cause maps onto a specific step in this cascade. The headline is that an erection is driven by nitric oxide and the relaxation of smooth muscle, which together let blood flow into the penis and then trap it there.

When a man is sexually stimulated — and stimulation begins in the brain, not the pelvis — the parasympathetic nerves trigger the release of nitric oxide, a signaling molecule that relaxes the smooth muscle in the walls of the penile arteries and the erectile bodies (the corpora cavernosa). Nitric oxide does this by activating the enzyme guanylate cyclase, which raises levels of cyclic GMP, the second messenger that actually drives smooth-muscle relaxation. As those muscles relax, arterial blood rushes in and engorges the sinusoidal spaces of the corpora cavernosa.

The second half of the mechanism is what keeps the erection rigid. As the corpora fill, they expand and compress the emissary veins that normally drain blood out of the penis. The tunica albuginea, the tough fibrous membrane wrapping the erectile bodies, becomes tense and acts like a valve — restricting venous outflow and trapping the blood inside. Inflow plus restricted outflow equals a sustained erection. To maintain it, the body keeps nitric oxide production going through a phosphorylation process involving protein kinase A and neuronal nitric oxide synthase.

Two of Dr. Greenleaf's teaching points are worth carrying into practice. The first is the role of the brain and the nervous system: erection is a parasympathetic, “rest-and-digest” function, and it cannot happen when the sympathetic “fight-or-flight” system is dominant. Stress, in her words, is the biggest killer of libido and function — “without brain stimulation, all the Viagra in the world will not function.” The second is the role of fibroblasts, the most abundant cell in the penis, which help regulate blood flow; the frequency of erections actually influences their number, which is part of the rationale behind penile rehabilitation. Both points explain why ED is so often multifactorial — and why a pill that only addresses blood flow will fail if the brain, the nerves, or the vasculature upstream are the real problem.

What causes ED

ED can stem from physical causes, psychological causes, or — most commonly — a combination of the two. Mapping causes onto the erection cascade above makes them easier to reason about. The major categories are:

• Vascular — by far the most common physical cause. Atherosclerosis, hypertension, dyslipidemia, and endothelial dysfunction impair the arterial inflow and nitric-oxide signaling that an erection depends on. Because the penile arteries are small, they often show disease before the larger coronary arteries do.
• Diabetes — a particularly important cause, damaging both the small vessels (impairing blood flow) and the nerves (impairing the signal to release nitric oxide). Diabetic ED is common, frequently more severe, and a strong prompt to evaluate overall metabolic and cardiovascular health.
• Hormonal / low testosterone — low testosterone can contribute to ED and to reduced desire, though the relationship is not one-to-one: many men with low testosterone have normal libido, and many men with ED have normal testosterone. Thyroid disorders and other endocrine problems can also contribute. See our companion guide on hormones and sexual function.
• Neurological — conditions that interrupt the nerve signaling required for erection, from spinal cord injury and herniated discs to neuropathy and central nervous system disease.
• Psychological — depression, anxiety, performance anxiety, relationship conflict, and chronic stress. These act through the sympathetic nervous system, which physiologically opposes erection. Psychogenic ED is suggested when nocturnal and morning erections are preserved.
• Medications and substances — a number of common drug classes and substance use can impair erectile function and are worth reviewing in every workup.

Because these causes overlap so often, the clinical task is less about finding a single culprit and more about identifying which systems are involved — the “whole body, mind, spirit” approach Dr. Greenleaf emphasizes — and treating the underlying disease, not just the symptom.

Why ED is a cardiovascular warning sign

If a provider takes one thing from this guide, it should be this: new-onset ED in a man without an obvious cause warrants cardiovascular evaluation. Dr. Greenleaf calls ED “the canary in the coal mine” for cardiovascular disease — and the evidence behind that phrase is compelling.

The logic is anatomical. The same atherosclerotic process that narrows the coronary arteries also narrows the much smaller arteries that supply the penis. Because those penile arteries are smaller, the same degree of plaque produces a noticeable functional deficit there first — often several years before overt heart disease declares itself. ED, in other words, can be the earliest clinical manifestation of systemic vascular disease.

The numbers Dr. Greenleaf cites make the point concrete. One study found that men in their 40s with erection problems but no other cardiovascular risk factors carried an 80% risk of developing heart disease in the future. Another found that men who developed ED over a seven-year follow-up were nearly twice as likely to subsequently experience a cardiovascular event such as a heart attack or stroke — a risk that appeared independent of age, cholesterol, blood pressure, diabetes, and smoking. Researchers have estimated that a meaningful share of cardiovascular events might have been avoided had men acted on prevention after first noticing ED symptoms.

Evaluating ED

A competent ED evaluation is methodical but not complicated, and it starts before any lab is drawn. The first step is building rapport in a trusting, non-judgmental, confidential setting — sexual concerns are chronically underreported because of embarrassment, and the quality of the history depends entirely on the patient's comfort.

The history establishes the onset, duration, and severity of symptoms, distinguishes gradual from abrupt onset, and screens for the categories above: cardiovascular and metabolic disease, diabetes, neurological symptoms, medications, substance use, and psychological and relationship factors. A useful clue lives in the history itself — preserved nocturnal and morning erections point toward a psychogenic component, whereas their absence suggests an organic, often vascular, cause. Validated instruments such as the International Index of Erectile Function help quantify severity and track response to treatment.

The physical exam is focused: inspection of the external genitalia for anatomical abnormalities or signs of Peyronie's disease, assessment of secondary sexual characteristics, evaluation of lower-extremity pulses as a window on the vascular system, and neurological checks such as the bulbocavernosus reflex and sphincter tone to assess the sacral reflex arc.

The laboratory workup is guided by the suspected cause but conceptually centers on the systems that produce an erection — a serum testosterone level (low testosterone can contribute to ED), screening for diabetes and other metabolic conditions, a lipid profile, thyroid studies where indicated, and prostate-specific antigen if relevant to the clinical picture. Specialized testing — nocturnal penile tumescence studies, penile Doppler ultrasound, intracavernosal injection testing — is reserved for cases where the cause is unclear or the patient does not respond to first-line therapy. The specific test selection, interpretation, and decision thresholds are taught in depth in Empire's course.

Treatment options for ED

The encouraging part of the ED conversation is that it is a highly treatable condition, with a deep and well-organized menu of options. The right choice depends on the underlying cause, severity, comorbidities, and patient preference. A sound approach generally moves from least to most invasive, while always treating any underlying vascular or metabolic disease in parallel.

Lifestyle and risk-factor modification

Because most ED is vascular, the interventions that protect the heart also help the erection. Dr. Greenleaf notes that regular exercise — even 30 minutes of walking a day — can improve ED symptoms substantially, and that a Mediterranean-style diet has outperformed a low-fat diet for erectile function in studies. Losing 5–10% of body weight in overweight men, quitting smoking, moderating alcohol, and addressing stress, anxiety, and depression all directly improve erectile function. This is the foundation every treatment plan should be built on, not an afterthought.

PDE5 inhibitors

Oral PDE5 inhibitors — sildenafil, tadalafil, vardenafil, and avanafil — are the first-line pharmacologic treatment for most men. They work downstream in the nitric-oxide pathway by blocking phosphodiesterase type 5, the enzyme that breaks down cyclic GMP. With PDE5 blocked, cyclic GMP accumulates, smooth muscle stays relaxed, and blood flow is enhanced. Critically, they do not create an erection on their own — they amplify the body's natural response, which is why sexual stimulation and brain engagement are still required. The four agents differ in onset and duration, and that profile drives selection; the details are covered in the linked guide.

Injections and devices

For men who don't respond to or can't tolerate oral therapy, intracavernosal injections and devices are highly effective second-line options. Injectable therapy — alprostadil alone or as compounded combinations such as bimix, trimix, and quadmix — produces an erection through direct vasodilation and works even when oral agents have failed. Vacuum erection devices, which draw blood into the penis mechanically and use a constriction band to maintain the erection, are a non-invasive, prescription-free option that suits men who cannot use or prefer to avoid medication. Both modalities require correct technique and patient counseling; specific agents, dosing, and procedural technique are taught in Empire's course rather than reproduced here.

Shockwave therapy

Low-intensity shockwave therapy is an emerging, regenerative-leaning option that uses acoustic energy to stimulate angiogenesis, tissue remodeling, and nitric oxide production in the penis. It is worth being evidence-honest here: while studies show a trend toward improved erectile function, the quality of evidence is still debated, optimal protocols are not standardized, and the Sexual Medicine Society of North America recommends it be used under research protocols pending more robust data. It is a promising, low-risk modality — not yet a settled standard of care.

Hormone optimization

Where testosterone is genuinely low and symptomatic, hormone optimization can be part of the picture — addressed in our guide to hormones and sexual function and, in greater depth, the testosterone replacement therapy guide in our hormone cluster. The caveat Dr. Greenleaf stresses is that hormones are “a tool, not the answer”: if stress and the underlying drivers are not addressed, optimizing a hormone level rarely fixes the problem on its own. For the central, libido-and-arousal dimension, the investigational melanocortin peptide PT-141 is another agent providers ask about.

For men with refractory ED who have exhausted these options, surgically placed penile implants remain a durable, high-satisfaction solution — a reminder that even the most resistant cases have an effective answer when evaluation and treatment are done well.

Training to evaluate and treat ED

ED sits at the intersection of cardiology, endocrinology, urology, and primary care, which is precisely why it is both a clinical opportunity and an area where structured training pays off. The competent management of ED is less about memorizing a drug list and more about reasoning through the cause: recognizing ED as a cardiovascular warning sign, taking a history that puts the patient at ease, ordering the right labs, and then selecting intelligently among PDE5 inhibitors, injection therapy, devices, shockwave, and hormone optimization based on the individual in front of you.

Empire's curriculum is built around exactly that clinical judgment. Developed by Dr. Betsy Greenleaf, DO — board-certified in OB/GYN and urogynecology and Empire's Director of Anti-Aging — the sexual dysfunction training teaches the physiology, evaluation, and treatment of ED and the broader field of sexual health, so providers can add a confident, evidence-based men's sexual health offering to their practice.