A man's prostate gland usually starts to enlarge after he reaches 40 years of age. This condition is called benign prostatic hyperplasia (BPH).

The prostate gland secretes a fluid that helps to nourish sperm. The gland itself surrounds the urethra, which is the tube that carries urine from the bladder out through the tip of the penis (see multimedia file 1). As the prostate grows larger, it may press on the urethra. This narrowing of the urethra can cause some men with prostate enlargement to have trouble with urination. Prostate enlargement may be the most common health problem in men older than 60 years of age.

With the process of aging, it is quite common for the prostate gland to become enlarged. As a man matures, the prostate goes through two main periods of growth. The first occurs early in puberty, during male genital development, when the prostate doubles in size.