1. The causes of BPH are incompletely understood.

2. Age is the most important factor 40% of men aged 50 may have evidence of BPH, and this increases further with age.

3. Studies on twins and families of men with BPE have shown a family history is important for more than half of BPE occur under 60 years of age. For men with relatives who require surgery for BPE, the risk for BPE-related surgery was increased four-fold.

4. Black men are more likely than white men to have BPE, whereas Asian men are less likely to have BPE.

5. BPE is associated with heart disease, the use of drugs known as beta-blockers.

6. Lack of physical exercise.

7. Fat appears to be important as it induces inflammation, which in turn causes BPE. BPE is more common in obese men, and certain dietary fats may induce inflammation.

8. Prostatitis, which is inflammation of the prostate, is associated with an enlarged prostate and BPE.

9. Relatively uniquely in the body, prostate tissue reverts to an embryonic state in which it is more sensitive to chemical signals, known as growth factors, in the fluid that bathes the cells. Consequently, the cells grow.