As a man grows older, characteristic changes begin to occur in the prostate. There is a cell build-up in its innermost core; the transition zone begins to grow. But the body’s hormone levels aren’t growing along with the prostate; in fact, there’s a drop in the amount of testosterone in the blood; DHT levels remain fairly steady, and there’s only a slight increase in estrogen. So why is the prostate getting larger? One reason, scientists believe, is that the aging prostate becomes more susceptible to these hormones. In laboratory experiments, scientists have shown that estrogen adds more power to testosterone’s punch, making it more effective. At the same time, the aging prostate becomes more sensitive to smaller amounts of testosterone. So some researchers believe that estrogen plus aging equals a prostate easily influenced by testosterone, even when there’s less of it in the body. In other words, the threshold is lowered.
But another big surprise in recent research is the discovery that growing prostates aren’t making scads of new cells. How can this be? If there’s not a huge increase in cell birth, what’s making the prostate grow? Apparendy, something’s also happening to cell death; the cells in question are leading abnormally long lives, and this is resulting in a cellular overcrowding, or population explosion.
Finally, scientists are beginning to investigate the role of substances called growth factors, which serve as switches that activate processes to promote cell division in this balance of cell birth and death. Investigators have found higher levels of some growth factors in tissue with BPH than in normal tissue. Current thinking is that these growth factors have a major impact on the stromal, or smooth muscle, cells. (These growth factors are produced by cells in the prostate and act locally, either on the cell of origin or on adjacent cells. One, such as basic fibroblast growth factor, is known to stimulate glandular cells to grow. Others, such as transforming growth factor-beta, stimulate the stromal and smooth muscle cells.)
Spurred by the growth factors, these cells somehow revert to a more primitive state, which allows proliferation of the lumpy masses of lobes in the prostatic tissue surrounding the urethra. Whatever stimulates the stromal cells also seems to restrain other cells, particularly the epithelial cells, the tiny factories that make the prostate’s secretions. This would explain two of BPH’s more significant characteristics: The build-up in cells and the drop in prostatic secretions.