The origin and development of benign prostatic hyperplasia. An age-dependent process.

Although the exact cause of benign prostatic hyperplasia (BPH) is not well defined, it is thought to occur as the result of epithelial-stromal interactions in the appropriate hormonal milieu. Benign prostatic hyperplasia originates in the periurethral and transition zones of the prostate in a microscopic (histologically identifiable) state as early as the third decade of life. With advancing age and the presence of androgens, approximately 50% of microscopic BPH will develop into macroscopic (palpably enlarged prostate) BPH. However, clinically significant BPH necessitating treatment will develop in only 50% of men with an enlarged prostate gland. In the United States, the estimated risk of a 50-year-old man undergoing a prostatectomy in his lifetime is approximately 25% to 40%. If left untreated, a significant number of symptomatic patients will remain stable or improve without adverse sequelae.