Pathophysiology
Clinical meaning
BPH involves hyperplasia of stromal and glandular elements in the periurethral transition zone of the prostate. Testosterone is converted to dihydrotestosterone (DHT) by 5-alpha-reductase within prostatic tissue. DHT binds androgen receptors with 5-fold greater affinity than testosterone, driving prostatic cell proliferation and gland enlargement. The enlarged prostate compresses the prostatic urethra causing bladder outlet obstruction (BOO). BOO produces both obstructive (hesitancy, weak stream, incomplete emptying, post-void dribbling) and irritative/storage symptoms (frequency, urgency, nocturia) collectively termed lower urinary tract symptoms (LUTS). Chronic BOO leads to detrusor hypertrophy, trabeculation, and eventually decompensation with overflow incontinence and urinary retention. The International Prostate Symptom Score (IPSS) quantifies severity: mild (0-7), moderate (8-19), severe (20-35).