Prostate Tissue and BPH
The prostate gland is composed mainly of two kinds of tissue -- glandular (about 20% to 30% of prostate tissue) and muscular (70% to 80%).
As men age, the prostate gradually increases in size as glandular tissue grows inside the gland -- a process that puts pressure on and obstructs the urethra. Also, prostate muscle tissue can become contracted, or tense, thus squeezing the urethra and neck of the bladder. When the normal flow of urine is blocked -- usually through a combination of both of these processes -- symptoms involving the lower urinary tract (bladder and urethra) may develop. This condition is known as benign prostatic hyperplasia (BPH). Glandular tissue growth is stimulated by dihydrotestosterone (DHT), a form of testosterone that is controlled by an enzyme called 5-alpha reductase.
The development of symptoms does not depend on the size of the prostate gland alone. Some men have normal-sized prostates with symptoms, while others have an enlarged prostate without symptoms. The presence or absence of muscular contraction may explain this difference.
The size of the prostate can be estimated by a digital rectal exam (DRE) and measured more precisely by transrectal ultrasound (TRUS) or magnetic resonance imaging (MRI).
The degree of prostate-associated muscular tension is more difficult to measure.
