The cause of BPH is not well understood, nor do we have good information on risk factors. It has been long known that BPH occurs mainly in older men and that it doesn't develop in men whose testes were removed before puberty. For this reason, some believe that factors related to aging and the testes may cause BPH.
Throughout their lives, men produce both testosterone, (male hormone), and small amounts of estrogen, a female hormone. As men age, the amount of testosterone in the blood diminishes, leaving a higher proportion of estrogen. Animal studies suggest that BPH may occur because the higher amount of estrogen increases the activity of substances that promote prostate cell growth.
Another theory focuses on dihydrotestosterone (DHT), a substance derived from testosterone in the prostate. It is felt that this may help control gland growth, and it has been found that most animals lose their ability to produce DHT as they age. Some research has indicated that even with a drop in the blood's testosterone level, older men continue to produce high levels of DHT and that this accumulation in the prostate may encourage the growth of cells. It has also been noted that men who do not produce DHT do not develop BPH.
Another theory is that BPH may develop as a result of "instructions" given to cells early in life. By this theory, BPH occurs because cells in one section of the gland follow such instructions and are reactivated later in life. These cells then deliver signals to other cells instructing them to grow or making them more sensitive to hormones.