Benign prostatic hyperplasia, or B-P-H, can happen when a small gland called the prostate causes bladder problems in men. B-P-H is very common in older men. By age 60, the majority of men have at least some symptoms of B-P-H. Causes. The prostate is a small gland that's part of the male reproductive system. It sits just below your bladder, which stores urine, and in front of the rectum. During ejaculation, the prostate squeezes fluid into your urethra, the tube that sends urine from the bladder out of the body. The fluid protects the sperm, and is part of the liquid that makes up semen. In young men, the prostate gland is about the size of a walnut. But it continues to grow throughout your adult life. As the prostate gland grows, it starts to press on the urethra, like a clamp on a garden hose. It also presses on the bladder and irritates it. Over time, the wall of the bladder weakens, and the bladder is unable to completely empty.