Finasteride Mechanism and Effects

Tissue-Specific Effects in BPH

The reduction in androgenic growth leads to increased apoptosis and atrophy, shrinking the prostate by 15-25% at six months, according to the American Urological Association 1
Atrophy is most pronounced in the glandular epithelial component of the prostate, which is the source of PSA production, reducing PSA levels by approximately 50%, as recommended by the European Association of Urology 1
The reduction in prostate volume provides clinical benefits including improved urinary flow rate and decreased obstructive and irritative symptoms, as stated by the American Urological Association 1

Unlike finasteride, which selectively inhibits Type II 5-alpha-reductase, dutasteride inhibits both Type I and Type II isoenzymes, resulting in finasteride reducing serum DHT by approximately 70% compared to 95% with dutasteride, according to the European Association of Urology 1
However, in BPH tissue where Type II 5-alpha-reductase is far more common than Type I, the reduction of DHT in prostate tissues is approximately 80% with finasteride and 94% with dutasteride, as reported by the American Urological Association 1

Due to the slow onset of action compared to alpha-blockers, patients should be counseled on slower symptom improvement if treated with finasteride alone for BPH, as recommended by the American Urological Association 1