Pathophysiology of Erectile Dysfunction

What is erectile dysfunction?

Persistent failure to achieve a penile erection too allow for satisfactory sexual intercourse.

• persistent: > 3 months

• Can have complete inability, inconsistent ability or erection for only brief period

What are other types of male sexual dysfunction?

• delayed ejaculation

• retrograde ejaculation (dry orgasm)

• decreased libido

• infertility

Prevalence of ED

• 50% in males 40-70

  • increases with increasing age

• marker for CV disease

Two main overarching causes for ED

• psychogenic

• organic

Types of psychogenic causes for ED

• performance anxiety

• traumatic past

• relationship problems

• depression, anxiety, stress

Types of organic causes for ED

• Vascular

  • CAD, HTN, DM, Dyslipidemia, smoking

• Neurologic

  • spine/brain injury, parkinsons, alzheimers, stroke

• Hormonal

  • hypogonadism, hyperprolactemia, thyroid or cortisol

• Local

  • peyronie’s, cavernous fibrosis, penile fracture

• Drugs

Drugs that can induce ED

• Antidepressants

  • SSRIs, MAOIs, TCAs

• Antihypertensives

  • Beta-blockers, verapamil, methyldopa, clonidine

• Cardiac agents

  • digoxin, amiodarone

• Diuretics

  • THZ, spironolactone

• Hormones

  • corticosteroids, ketoconazole, antiandrogens, LHRH agonists

• H2RAs

  • cimetidine, ranitidine

• recreational drugs

  • alcohol, marijuana, cocaine

What 3 systems are required in a normal penile erection?

• vascular

• nervous

• hormonal

How does the vascular system aid in getting an erection?

• Flaccid state

  • arterial blood in and out of corpora cavernosa

• Erect state

  • decrease venous outflow and increase arterial inflow

  • via ACh-mediated vasodilation + cGMP/cAMP

How does the nervous system aid in getting an erection?

• Sacral nerve reflex arc

• external stimuli integration via hypothalamus

• Dopamine exerts proerectogenic effect

• alpha2-adrenergic stimulation is anti-erectogenic

How does the hormonal system aid in getting an erection?

• testosterone stimulate libido

• androgen receptors in penile arterial endothelium may increase, nitrous oxide and cGMP, enhancing erection

ED pathogenesis

• a single abnormality or multi system abnormalities may result in organic erectile dysfunction (80%)

• drug-induced ED (10-25%)

• If no organic cause, and no response to psychogenic stimuli then psychogenic ED

Clinical presentations of ED

• general

  • relationship problems

  • performance anxiety

• symptoms

  • ED ± decreased libido

• Signs

  • low satisfaction of quality of erection

  • potential comorbidities: hypogonadism, curved penis, decreased pelvic pulse, decreased anal sphincter tone

• Lab tests

  • low T

  • enlarged prostate via DRE

  • high PSA

Investigations done for ED

• sexual history

  • severity, onset and duration

  • questionnaire - IIEF or SHIM

• Medical history

  • vascular comorbidities or surgical procedures

• Medication history

• Physical exam

  • signs of hypogonadism, abnormal penile anatomy, reduced nerve function

• Lab tests

  • FBG, A1C, lipids

  • Testosterone if > 50 or younger w/ decreased libido