As men move into middle age, the prostate is increasingly likely to become a source of problems.

The problem most often encountered by younger men is prostatitis, which means inflammation of the prostate gland. Prostatitis accounts for about one-quarter of visits by younger and middle-aged men to a doctor for urinary trouble.

Prostatitis may be acute, meaning that it is sudden and severe, or it can be chronic -- slow to develop but hard to get rid of, lingering for months and reappearing over the years.

Once past the age of 40, the most common of the prostate problems is benign prostatic hyperplasia (BPH), an enlargement of the prostate that may cause difficulty in urination.

While benign means non-cancerous, hyperplasia means excess growth -- in this case an abnormal multiplication of non-malignant prostate cells. Although cancer is also characterized by excess growth, there is no evidence to suggest that BPH leads to prostate cancer.

Some 80 percent of men eventually will develop enlarged prostates if they live into their 70s, with many in later years developing symptoms that require treatment. But BPH is for the most part not life threatening.

That is not, however, the case with prostate cancer, which is now the second-leading cause of cancer deaths among men in the United States.

Unlike BPH, in which the excess growth is confined to the prostate gland, a cancer is characterized by uncontrolled growth of abnormal cells. Initially, the cancer cells are confined within the prostate ducts and glans. But undetected and unchecked, the cells with time can spread into the blood and lymphatic system and metastacize to other parts of the body.

If prostate cancer is detected early, when it's confined to the prostate, chances of successful treatment are increasingly promising.