creation date: 2025-06-24 22:08
tags: Pathologies
Erectile Dysfunction
Background
Definitions
Erectile dysfunction is the most common form of male sexual dysfunction. It is defined as the consistent or recurrent inability to acquire or sustain an erection of sufficient rigidity and duration for sexual intercourse.
Normal Physiology
Normal male function requires interaction between vascular, neurologic, hormonal, and psychological systems.
The acquisition and maintenance of erection is primarily vascular, but is triggered by neurological signals that is mediated by presence of appropriate hormones and psychological mindset.
Neural impulses are the trigger for initiation of erection.
- Psychogenic erections are triggered by impulses from the paraventricular nucleus and medial preoptic area of the hypothalamus as a result of sexual images (eg. visual/auditory stimuli, fantasy). The impulse travels to a neural centre at T11 to L2 and then to the pelvic vascular bed, redirecting blood to the corpora cavernosa.
- Reflex erections are from tactile stimulus to the penis or genital area, activating a reflex arc with sacral roots at S2-S4.
- Nonsexual, nocturnal erections occur during REM sleep and occur 3-4 times nightly and may be present on awakening. (Myth: due to full bladder; false)
Maintenance of an erection requires blood to flow from the hypogastric arterial system into the intracavernosa. As flow increases, the pressure within the intracavernosal spaces increases which prevents penile venous outflow from emissary veins.
Intrapenile nitric oxide act as local neurotransmitter which stimulates generation of cyclic GMP. This relaxes the trabeculae which maximizes blood flow and engorgement. Nitric oxide is generated by nitric oxide synthase.
Testosterone is important for both libido and the maintenance of nitric oxide synthase levels.
Detumescence (loss of erection) occurs when cyclic GMP is metabolized by intracavernosal type 5 cyclic GMP phosphodiesterase. This pathway is also regulated by norepinephrine pathways.
Etiology
ED can be a symptom of a variety of underlying pathologies. On its own, cause is often multifactorial. Etiology can be separated as either an underlying psychological cause such as:
- Depression
- Performance anxiety
- Sexual disorders
or an organic cause which can be any disease process that affects penile arteries, nerves, hormone levels (testosterone, hyperprolactinemia, thyroid), smooth muscle tissue, corporal endothelium, or tunica albuginea. Examples of conditions related to ED include: - Cardiovascular disease
- Diabetes mellitus
- Hypertension
- Multiple sclerosis
- Thyroid disease
- Spinal cord injuries
Medication may also cause ED such as:
- Antihypertensives
- Anti-androgens
It should be noted that psychological and organic causes are not mutually exclusive. In cases of organic etiology, there is almost certainly a psychological component due to norms, expectations, shame, and relationship issues that may occur as a result.
Pathogenesis
ED would arise if any of the normal physiology is disrupted.
This may be due to a disruption in psychological factors such as stress, neurological disruptions such as spinal cord injury or testosterone deficiency. Vascular obstructions may also result in ED.
Clinical Presentation
Signs & Symptoms
Presenting complaint is the inability to maintain or have erection.
History & Physical Exam
A through history is needed. This includes medical history, detailed sexual history, obtaining an complete medication list incl. supplements.
It is important to assess the degree of erectile rigidity (eg. 0-10 scale) and to track with treatment.
Sexual history questions include but not limited to:
- Degree of rigidity
- Duration of erection
- When rigidity is lost (eg. foreplay, before penetration)
- Presence of morning erections/overnight erections
- Onset (gradual vs sudden which almost always is psychogenic)
A questionnaire such as the International Index of Erectile Function Questionnaire (IIEF) can be used for the patient to fill out privately.
It is important to also complete a general cardiovascular examination as ED can be the first symptom of underlying vascular or heart disease, including femoral and peripheral pulses.
Examination should also include examining for the lack of normal male hair patterns, gynecomastia, and small testes. The cremasteric reflex should also be elicited.
Risk factors
Medical history of:
- Cardiovascular disease
- Diabetes mellitus
- Hypertension
- Obesity
- Dyslipidemia
- Hypogonadism
- Depression
- Pelvic floor disorders
- Sleep disorders
Other factors include:
- Smoking
- Certain medication use
Inconclusively, pornography use and bicycling may be related to ED.
Diagnosis
Criteria
Diagnosis is made clinically.
Work-up
It may be relevant to distinguish between etiology of ED and to verify that the patient does have ED and not another form of sexual dysfunction such as premature ejaculation.
Identifying psychogenic and/or mental health etiologies can direct management.
There are no routine tests for evaluation of ED but it is common for routine bloodwork to be completed which includes:
- CBC
- Electrolytes
- Renal and liver function
- A1C for diabetes screening
- Lipid profile
A morning testosterone level may be considered to rule out hypogonadism, especially if PDE-5 therapy does not work.
Further testing may be available but is optional includes:
- Penile biothesiometry (sensitivity to vibration)
- Nocturnal tumescence testing (evaluates nocturnal erections)
- Penile duplex Doppler ultrasound (vascular flow)
Differential
Diagnoses that may present with a similar complaint include other forms of sexual dysfunction:
- Low libido
- Ejaculatory disorders (premature ejaculation, retrograde ejaculation)
Red Flags / Complications
Strain on relationship and negative quality of life can be direct consequences of ED.
Other complications may arise should an underlying cause go untreated, especially cardiovascular pathologies and diabetic complications.
Management
Lifestyle / Social
Initial treatment involves improving general health such as:
- Increasing physical activity
- Improving diet (eg. Mediterranean diet)
- Cessation of smoking, drugs, and alcohol
- Controlling conditions such as diabetes, lipids, cholesterol
Supplementation of L-arginine may be efficacious as it is a substrate for producing nitric oxide synthase.
Pharmacological / Interventional
Eroxon, an OTC topical gel, may be considered for treatment initially before prescription medication.
First line treatment uses phosphodiesterase-5 (PDE-5) inhibitor. Efficacy are similar between choices:
- Sidenafil (Viagara) 50mg PO prn
- Ideally 1 hr before sexual intercourse on empty stomach
- 4 hour duration
- Dose can be adjusted between 25-100mg
- Vardenafil (Levitra)
- 4 hour duration
- Similar structure to sidenafil
- Tadalafil (Cialis) 10mg PO
- Longer duration of action
- Different structure to above
- Dose can be adjusted between 5-20mg
- Low dose (2.5-5mg) option available for once-daily use if prn dosing insuffiencient
In cases of psychogenic ED, consider psychotherapy. It should be noted use of SSRI can decrease libido and erectile function. In these cases, low-dose of tadalafil, continuously can be used.
Additional treatment options can be considered:
- Testosterone replacement
- Vacuum-assisted erection devices
- Penile self-injections of alprostadil and papverine
- Intraurethral alprostadil
- Surgical prostheses or revascularization