The prostate typically enlarges due to a condition known as benign prostatic hyperplasia (BPH), which is a common occurrence in aging men. BPH involves non-cancerous growth of the prostate gland, leading to its enlargement. The exact cause of BPH is not fully understood, but it is believed to be influenced by hormonal changes, particularly the conversion of testosterone to dihydrotestosterone (DHT), as well as aging and genetics.

Other factors that may contribute to prostate enlargement include inflammation of the prostate gland (prostatitis), urinary tract infections, and lifestyle factors such as obesity and lack of physical activity. However, BPH remains the most common cause of prostate enlargement in men as they age.