Erectile Dysfunction Mechanism – Quick Pharmacology Notes for GPAT, NEETPG, Nursing exams

Definition:

Erectile dysfunction (ED) is the inability to achieve or maintain an erection sufficient for satisfactory sexual performance.

Normal Physiology of Erection:

1. Sexual stimulation → triggers parasympathetic nervous system.

2. Release of Nitric Oxide (NO) from endothelial cells & nerves.

3. NO activates guanylyl cyclase → ↑ cGMP.

4. cGMP causes smooth muscle relaxation in corpora cavernosa.

5. Relaxation → vasodilation → ↑ blood flow → erection.

Mechanism of Erectile Dysfunction:

• Impaired NO release or cGMP production.

• Increased PDE-5 activity → breaks down cGMP → prevents erection.

• Reduced blood flow (due to atherosclerosis, hypertension).

• Neurological causes: e.g. diabetes, spinal cord injury.

• Hormonal imbalance: low testosterone.

• Psychogenic factors: stress, anxiety.

• Drug-induced: antidepressants, beta-blockers, etc.

• Participate in GPAT MOCK TEST: Click Here

Treatment Mechanism (e.g., Sildenafil):

• PDE-5 inhibitors block phosphodiesterase-5 → prevent cGMP breakdown → sustained erection.

MCQs on Erectile Dysfunction

GET MORE MCQ: Click Here

1. Which enzyme breaks down cGMP in the corpus cavernosum, contributing to erectile dysfunction?
a. Nitric oxide synthase
b. Guanylyl cyclase
c. Phosphodiesterase-5 (PDE-5)
d. Adenylate cyclase
Answer: c. Phosphodiesterase-5 (PDE-5)

2. Sildenafil acts by:
a. Stimulating NO synthesis
b. Inhibiting PDE-5
c. Increasing testosterone secretion
d. Blocking adrenergic receptors
Answer: b. Inhibiting PDE-5

3. Which of the following is not a cause of erectile dysfunction?
a. Diabetes mellitus
b. Hypertension
c. Hyperthyroidism
d. Spinal cord injury
Answer: c. Hyperthyroidism

4. The primary neurotransmitter involved in initiating an erection is:
a. Acetylcholine
b. Dopamine
c. Nitric oxide
d. Serotonin
Answer: c. Nitric oxide