At birth, a boy's prostate gland is about the size of a pea. It grows slightly during childhood and then at puberty undergoes a rapid growth spurt. By the time a man reaches age 25, his prostate is fully developed and is about the size of a walnut.

The causes of noncancerous growth of tissue inside the prostate later in life are unclear. Researchers believe that with age, the prostate becomes more susceptible to the effects of male hormones, including testosterone.

The main risk factor for prostate enlargement is aging. Prostate enlargement rarely causes signs and symptoms in men younger than 40, but approximately half the men in their 60s experience some signs and symptoms. In addition to age, other risk factors include:

• Heredity. A family history of prostate enlargement can increase the odds of developing problems from prostate enlargement.

• National origin. Prostate enlargement is more common in American and European men than in Asian men.

• Marital status. For unknown reasons, married men are more likely to experience prostate enlargement than are single men. There's no evidence that supports a link between sexual activity and prostate growth.

If you're experiencing urinary problems, seek medical advice. Your doctor can help determine whether you have prostate enlargement and whether your symptoms warrant evaluation and treatment.

If you don't find your symptoms troublesome and they don't pose a health threat, you may not need treatment. That doesn't mean that it's all right to let urinary symptoms go without medical evaluation. Instead of prostate enlargement, your symptoms could be early warnings of a more serious condition, including a bladder stone, a bladder infection, side effects of medication, heart failure, diabetes, a neurologic problem, inflammation of the prostate (prostatitis) or prostate cancer.

• Heart failure

• Prostate cancer

• Prostatitis