prostate

prostate The prostate gland surrounds the urinary passage at the exit of the male bladder. The gland is very small in babies and grows at the time of puberty in response to testosterone secreted by the testicles. The function of the prostate is to secrete fluid which together with secretions from the seminal vesicles makes up most of the volume of the seminal fluid. The functions of seminal fluid are incompletely understood and more than a hundred compounds have been isolated from it. The gland has given its name to the group of substances known as prostaglandins, first identified at this site, but now known to be present throughout the body; prostaglandins in the seminal fluid may cause contractions of the female genital tract, facilitating transport of sperm through the uterus to the Fallopian tubes. The fluid also helps with the nutrition of sperm and defence against infection. The ejaculate forms a clot which sticks to the mucus of the cervix, enabling the passage of sperm into the mucus, through which they can travel to enter the uterus. An enzyme called prostatic specific antigen (PSA) then liquefies the sperm clot and the seminal fluid subsequently seeps out of the vagina. PSA is produced by the lining cells of prostate ducts and a small amount can be detected circulating in the blood. Any condition that increases prostate cells, such as benign enlargement of the prostate, or cancer, or any condition which causes leakiness of the cells such as prostatitis, results in increased levels of PSA in the blood. Very high levels of PSA usually indicate cancer, but moderately raised levels may indicate a whole variety of prostate disorders. There is worldwide research on the merits of PSA estimation as a screening test for prostate cancer but because increased levels may occur in a number of prostate disorders it can never be a perfect test.

Most men remain unaware of their prostate until late middle age when enlargement interferes with urination by constricting the urethra and reducing urine flow. This is often associated with the need to rise at night and pass urine more frequently. For more minor symptoms, there is effective drug treatment. When the symptoms become sufficiently disabling the usual treatment is an operation. The current lifetime chance of requiring a prostate operation is about one in ten. Prostate cancer is very common in elderly men and is a significant cause of premature death, but the paradox is that many more men have prostate cancer than die of it. Benign enlargement of the prostate and in some cases, cancer, can be treated by operations to remove part, or in cancer cases, the whole of the prostate. Many men fear these operations will result in impotence. In most cases of benign enlargement of the prostate there is no danger of impotence. Removal of part or all of the prostate does however result in a lack of external ejaculation because the junctions between the genital and urinary tracts lie within the prostate. In operations to remove the gland completely, it is possible for the nerves to the penis to be damaged, since they run close to the prostate. For many men with prostate cancer, total removal by operation is not feasible and the mainstay of treatment is to give hormones. Both the normal and the cancerous prostate grow in response to testosterone and the strategy of hormone treatments is to deprive the cancer of male hormone. This can be done in a number of different ways, both by blocking production of testosterone and by blocking its action. Hormone treatments are not curative but they may remain effective for many years.

Tim Hargreave

Bibliography

Rous, S. (1995). Prostate book. Norton, New York.

See urogenital system.See also ejaculation; semen; sex hormones.