It isn’t totally clear what it is that causes the prostate to enlarge. It might be due to changes in the balance of sex hormones as men grow older.

During their lives men produce testosterone, a male hormone together with small amounts of estrogen, a female hormone. As they age, the amount of active testosterone in men’s blood decreases leaving a higher percentage of estrogen. Some scientific studies have suggested that BPH may occur because this higher percentage of estrogen within the prostate increases the activity of substances that promote prostate cell growth.

A different theory looks at the effects of dihydrotestosterone (DHT). DHT is a hormone that stimulates the development of male characteristics and plays a role in prostate development and growth. Some research has shown that despite a drop in blood testosterone levels, older men continue to produce and accumulate high levels of DHT in the prostate and that this may encourage prostate cells to continue growing. Research has shown that men who do not produce DHT do not develop BPH.

Other factors that may indicate that you could be more likely to develop BPH include:

• A family history of BPH
• Medical conditions such as obesity, heart and circulatory disease, and type 2 diabetes
• Lack of physical exercise
• Erectile dysfunction