Erectile Dysfunction (ED)

Overview

• Definition: Inability to develop or maintain an erection during sex, also called impotence.
• Prevalence: Commonly increases with age.
• Social Impact: Can carry emotional and psychological stigma.

Sexual Response Cycle

1. Excitement Phase
   • Muscle tension, heart rate, blood flow to genitals increases (erection in males).
2. Plateau Phase
   • Maximal levels of excitement.
3. Orgasm Phase
   • Release of sexual tension, ejaculation in males.
4. Resolution Phase
   • Body returns to unexcited state.

Anatomy of the Penis

• Three cylindrical bodies
  • Corpus spongiosum surrounds the urethra.
  • Two corpora cavernosa made of erectile tissue, wrapped in tunica albuginea.
  • Cavernosal spaces within corpora cavernosa, lined with endothelial cells and smooth muscle.
• Blood Supply
  • Supplied by deep artery and smaller arteries to cavernosal spaces.
  • Drained by emissary veins into deep dorsal vein.
• Nervous Supply
  • Somatic and autonomic innervation via cavernous nerves.
  • Mnemonic: Point and Shoot (Parasympathetic causes erection, Sympathetic causes ejaculation).

Mechanisms of Erection

• Reflex Erection: Physical stimulation of genitals.
• Psychogenic Erection: Emotional stimulation via thought.
• Biochemical Pathway
  • Parasympathetic fibers release acetylcholine.
  • Acetylcholine activates nitric oxide synthase (NOS).
  • NOS converts arginine to citrulline and nitric oxide (NO).
  • NO activates guanylate cyclase, converting GTP to cGMP.
  • cGMP decreases intracellular calcium, relaxing smooth muscle.
  • Cavernosal spaces fill with blood, veins compress, erection is maintained.

Causes of Erectile Dysfunction

• Psychological Factors: Stress, performance anxiety, depression.
• Vascular Causes
  • Atherosclerosis: Plaques harden arteries, impair dilation.
  • Hypertension: Damages endothelial cells, reduces NO production.
  • Diabetes Mellitus: Hyaline deposits and thickened capillary walls cause hypoxia and smooth muscle death.
• Neurological Causes: CNS damage (stroke, multiple sclerosis, trauma), Prostate surgery.
• Endocrine Causes: Low testosterone (hypogonadism) linked to low NO synthase.
• Medications: Diuretics reduce circulating fluid; antidepressants, methadone (mechanism less understood).

Diagnosis

• No specific test; relies on sexual history and identification of stressors.
• Additional tests: Blood tests (testosterone, glucose), neurological assessment, duplex ultrasound.

Treatment Options

• Medications: PDE5 inhibitors (e.g., sildenafil) increase cGMP levels, promote smooth muscle relaxation.
• Devices: Vacuum erection devices use negative pressure to draw blood.
• Surgery: Prosthetic implants to maintain rigidity.

Recap

• ED is the inability to achieve or maintain an erection.
• Causes: Psychological, cardiovascular, neurological, hormonal, and medication side effects.
• Diagnosis: Based on history and tests for underlying causes.
• Treatments: Medication, devices, surgery.