Prostate gland enlargement

Townsend Letter for Doctors and Patients, May, 2006 by Martin W. Banschbach

The prostate gland is about the size and shape of a walnut and weighs in at around one ounce. Women seem to know more about this little gland than men do. About 11% of men don't know that they have this gland in their body. Only 15% of men have ever heard of the term prostatitis. Of the men who do know about prostatitis (inflammation of the prostate), about 16% of them think that this condition occurs in both men and women. About 50% of men will experience prostatitis during their lifetime, and one in four men will have benign prostatic hyperplasia (BPH) by the age of 50. (1)

Three major problems can occur in the prostate gland. Prostatitis, BPH, or cancer. A man could experience all three conditions during his lifetime. Because so few American men know anything at all about their prostate gland, the American Urological Association Foundation has set September of 2006 as Prostate Health Month with low-cost or no-cost prostate screening available throughout the United States. This will be the eighth year that this program has been in place in the US.

This article focuses on BPH (Benign Prostatic Hyperplasia). Because the prostate gland causes more problems in men than any other tissue in the male body, we need to spend a considerable amount of time covering this tiny male gland. BPH involves enlargement of the prostate gland. This tissue expansion appears to be unique to humans. (2) The prostate gland is located just below the bladder and in front of the rectum. The gland surrounds part of the urethra, which is a narrow tube that allows urine to pass from the bladder through the male penis. It's composed of 30 to 50 branched glands that each produce fluid that will be used to transport sperm. A fibroelastic capsule surrounds the gland. This capsule and the interior stroma contain smooth muscle cells that contract to expel the prostatic fluid during ejaculation. About 30% of the prostate gland is smooth muscle tissue.

Prostate fluid contains zinc, potassium, citric acid, fructose, spermine, cholesterol, phospholipids, prostaglandins, fibrinogenase, fibrinolysin, acid phosphatase, and other proteins in an alkaline fluid. This fluid is thought to help protect the sperm in the acidic vagina and also to provide the sperm with fuel. Since the vagina is colonized with bacteria, prostate fluid is also thought to help protect the male urethra from infection after intercourse.

The prostate gland consists of three different zones. The peripheral zone is the outside region of the prostate gland, and almost all prostate cancer starts in the peripheral zone. A physician, during a digital rectal examination, can feel this outer zone of the prostate; however, for cancer detection, a serum prostate specific antigen (PSA) can sometimes indicate prostate cancer before any lumps or firm areas in the prostate can be detected by a physician during the physical exam of the prostate.

PSA is a normal glycoprotein component of human male blood that is formed in the prostate gland with some escaping into the blood. PSA is actually a serine protease (an enzyme that can hydrolyze peptides or proteins). Epithelial cells in the prostate produce PSA, which will cleave insulin-like growth factor-binding protein-3 to decrease its affinity (binding) for insulin-like growth factor-I (IGF-I). (3) IGF-I is a common component of the human diet, and it may play a role in prostate cancer and prostate enlargement. (4) IGF-I can be found in the milk of all animal species where it appears to be used to promote animal growth, but IGF-I is also produced in the human body even if milk or dairy products are not part of a person's diet.

A PSA level of zero (none detected) to 4 ng/ml is usually considered to be normal for most men. An increase in the size of the prostate is considered to be part of the aging process in men, and with this increase in size comes more PSA. It's common to see a PSA level around 6.5 ng/ml in men over the age of 70. With prostate cancer, the PSA level tends to go up much higher than what you would see with prostate enlargement (BPH).

There are actually different forms of PSA. The main form that the prostate produces, and which is elevated in BPH, is used to hydrolyze the seminal fluid gel formed after ejaculation to allow the sperm to break free and swim around. Cancer cells produce another form of PSA. This form appears to allow the cancer cells to be more invasive and have a greater metastatic potential. (5) The cancer-specific PSA is referred to as Pro PSA. Pro PSA can be measured, (6) but it's still too early to tell if this will result in an improvement in the early detection of prostate cancer. (7)

During a digital rectal examination, a physician may be able to detect that the prostate gland is larger than normal. The transition zone in the prostate gland is only five percent of the total mass of the prostate, but this is the area where BPH occurs. The transition zone is under the peripheral zone and on top of the central zone in the prostate gland. Exactly why the cells present in the transition zone start to divide around the age of 40 is not known.