Introduction
Erectile dysfunction (ED) is defined as the persistent inability to achieve or maintain an erection sufficient for satisfactory sexual performance. It is highly prevalent, affecting up to 50% of men over the age of 40, with incidence increasing with age.
ED has major implications for psychological health, intimate relationships, and overall well-being. Importantly, it can be the first sign of systemic vascular disease, making its evaluation and management clinically significant.
Physiology of Penile Erection
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Neurovascular event involving interaction between vascular, neurological, hormonal, and psychological factors.
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Sexual stimulation → release of nitric oxide (NO) → increased cyclic guanosine monophosphate (cGMP) → smooth muscle relaxation in corpora cavernosa → arterial dilation → increased blood inflow → erection.
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Detumescence (loss of erection): Breakdown of cGMP by phosphodiesterase type 5 (PDE5) → smooth muscle contraction.
Causes of Erectile Dysfunction
1. Vascular Causes
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Atherosclerosis, hypertension, diabetes mellitus, hyperlipidemia (impair blood flow).
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ED often precedes coronary artery disease by 2–5 years.
2. Neurological Causes
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Spinal cord injuries, multiple sclerosis, Parkinson’s disease, peripheral neuropathy (often diabetic).
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Pelvic surgery or radiation (nerve injury).
3. Hormonal/Endocrine Causes
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Hypogonadism (low testosterone).
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Hyperprolactinemia.
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Thyroid disorders (hyper- or hypothyroidism).
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Cushing’s syndrome.
4. Psychological Causes
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Stress, anxiety, depression, performance anxiety.
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Relationship issues.
5. Medications
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Antihypertensives (beta-blockers, thiazides).
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Antidepressants (SSRIs, TCAs).
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Antipsychotics.
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Antiandrogens, opioids, alcohol.
6. Lifestyle Factors
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Smoking, alcohol abuse, sedentary lifestyle, obesity.
Clinical Features
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Inability to obtain or maintain an erection.
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Reduced libido (if hypogonadism or psychological cause).
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Premature or delayed ejaculation may coexist.
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May be situational (psychogenic) or consistent (organic).
Diagnostic Approach
1. History
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Onset, duration, severity.
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Nocturnal/morning erections (present in psychogenic ED, absent in organic).
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Associated risk factors (diabetes, hypertension, smoking).
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Medication history.
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Psychosocial and relationship assessment.
2. Physical Examination
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Cardiovascular exam (pulses, BP).
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Genital exam (testicular atrophy, Peyronie’s disease, penile deformity).
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Secondary sexual characteristics (hypogonadism).
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Neurological exam (peripheral neuropathy).
3. Laboratory Tests
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Fasting blood glucose, HbA1c.
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Lipid profile.
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Serum total testosterone (morning sample).
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Prolactin, LH, FSH (if low testosterone).
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TSH (thyroid dysfunction).
4. Specialized Tests (if needed)
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Nocturnal penile tumescence testing: Differentiates psychogenic from organic ED.
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Penile Doppler ultrasound: Evaluates arterial inflow/venous leak.
Management and Treatment
A. General and Lifestyle Measures
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Stop smoking, limit alcohol.
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Weight loss, regular exercise.
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Optimize control of diabetes, hypertension, lipids.
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Counseling for psychological/relationship issues.
B. Pharmacological Therapy
1. Phosphodiesterase-5 (PDE5) Inhibitors – First-Line
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Enhance NO-cGMP pathway → smooth muscle relaxation → erection.
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Taken on demand, require sexual stimulation to be effective.
Examples:
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Sildenafil: 50 mg orally, 1 hour before intercourse (range 25–100 mg). Duration 4–6 hours.
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Tadalafil: 10–20 mg orally, 30 minutes before intercourse (range 5–20 mg). Duration up to 36 hours.
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Vardenafil: 10 mg orally, 1 hour before intercourse (range 5–20 mg). Duration 4–6 hours.
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Avanafil: 100 mg orally, 30 minutes before intercourse (range 50–200 mg).
Contraindications:
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Concomitant nitrate therapy (severe hypotension).
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Use with caution in severe cardiac disease, recent MI/stroke.
2. Hormone Therapy
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Testosterone replacement for men with documented hypogonadism (low testosterone and symptoms).
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Formulations:
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Testosterone enanthate 100–200 mg intramuscular injection every 2–3 weeks.
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Transdermal testosterone gel 50 mg applied daily.
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Not recommended in men with normal testosterone levels.
3. Intracavernosal and Intraurethral Therapy
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Alprostadil (Prostaglandin E1):
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Intracavernosal injection: 2.5–20 mcg injected into corpora cavernosa before intercourse.
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Intraurethral suppository: 125–1000 mcg inserted 10 minutes before intercourse.
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Success rate ~70–80%.
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Side effects: penile pain, priapism, fibrosis.
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Combination injections (Trimix): Alprostadil + Papaverine + Phentolamine (specialist use).
4. Second-Line Oral/Adjunctive Agents
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Bupropion (antidepressant with dopaminergic effect): 150–300 mg orally daily, especially if ED due to SSRIs.
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Cabergoline (dopamine agonist): 0.25–0.5 mg twice weekly, for hyperprolactinemia-related ED.
C. Mechanical Devices
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Vacuum Erection Devices (VEDs): Negative pressure draws blood into penis, constriction ring maintains erection.
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Effective, non-invasive, but some men find them cumbersome.
D. Surgical Options
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Penile Prosthesis (Implants):
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Inflatable or malleable devices surgically implanted.
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High satisfaction rates when other therapies fail.
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Vascular surgery: Rarely indicated, for young men with focal arterial injury.
Complications of ED
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Psychological: depression, anxiety, relationship strain.
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Physical: priapism (from injections), side effects from medications.
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Underlying disease progression (cardiovascular disease if untreated).
Prognosis
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Depends on cause and adherence to treatment.
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Most men respond to PDE5 inhibitors.
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Hypogonadal men improve with testosterone replacement.
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For refractory cases, implants provide durable solution.
Patient Education
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ED is often an early warning sign of cardiovascular disease.
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Lifestyle changes are as important as medications.
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PDE5 inhibitors require sexual stimulation to work.
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Do not combine PDE5 inhibitors with nitrates.
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Seek medical care if erection lasts >4 hours (priapism).
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