The prostate is a walnut sized gland that sits just below the bladder in men and is an integral part of the male reproductive system. Made up of two lobes and enclosed by a layer of tissue, the prostate goes through two main periods of growth. The first occurs early in puberty, when the prostate doubles in size. At around the age of 25, the gland begins to grow again. This second growth phase often results in what is identified as an enlarged prostate.
As the prostate gets larger, the layer of tissue surrounding it stops it from expanding, causing the gland to press against the urethra. While the data varies, it is believed that most men over the age of 45 experience some amount of prostate enlargement, but may live symptom free. This enlargement is usually harmless, but it often results in problems urinating later on in life. By 60, it is believed that 80% of all men experience some sort of urinary interference due to prostate enlargement.