Knowledge of the anatomic division of the prostate is impoant in understanding the locations of the major pathologic diseases of the prostate. Most adenocarcinomas of the prostate originate in the peripheral zone, while hyperplastic nodules originate in the transition zone. This anatomic differentiation is the result of the physiologic fact that the transition zone is paicularly estrogen-sensitive, while the peripheral zone is paicularly androgensensitive. Dihydrotestosterone (DHT), which is formed from testosterone by the action of 5-a-reductase, is responsible for the development of the prostate during fetal growth and also at the time of pubey. With aging, DHT levels are increased in the prostate, where DHT binds to nuclear DNA and causes prostatic hyperplasia. This hyperplastic effect by DHT is augmented by estrogen, which appears to function by induction of androgen receptors, and therefore this hyperplasia occurs in the poion of the prostate that is paicularly estrogen-sensitive. Reference: Robbins & Cotran Pathologic Basis of Disease, 9edition