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 condition has also been referred to as benign prostatic hypertrophy.

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. 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.

The prostate grows larger due to an increase in the number of cells (hyperplasia). However, the precise reason for this increase is unknown.

A variety of factors may be involved, including androgens (male hormones), estrogens, growth factors and other cell signaling pathways.

BPH is a benign (noncancerous) enlargement of the prostate that blocks the flow of urine through the urethra. The prostate cells gradually multiply, creating an enlargement that puts pressure on the urethra — the “chute” through which urine and semen exit the body.

As the urethra narrows, the has to contract more forcefully to push urine through the body.

Over time, the bladder muscle may gradually become stronger, thicker, and overly sensitive; it begins to contract even when it contains small amounts of urine, causing a need to urinate frequently.

Eventually, the bladder muscle cannot overcome the effect of the narrowed urethra so urine remains in the bladder and it is not completely emptied.