The prostate is a small gland located in the male pelvis, positioned just below the bladder and in front of the rectum. Its primary function is to produce seminal fluid, which nourishes and transports sperm during ejaculation. Because the prostate surrounds the urethra, its size is a direct indicator of urinary tract health. Monitoring prostate volume is a standard part of male health screening, as changes can lead to functional issues.
Defining Normal Prostate Volume by Age
In young adulthood, the prostate gland typically reaches its mature size, often compared to a walnut. This corresponds to a volume of about 20 to 25 cubic centimeters (cc), which is standard for men under 40 years old.
The prostate naturally begins to increase in volume as a man ages, a process that continues throughout life. For men aged 40 to 60, a volume up to 30 cc is considered typical. After age 60, the average volume trends upward, commonly falling between 30 and 40 cc.
How Prostate Volume is Determined
Determining prostate volume often begins with a physical screening, such as the Digital Rectal Exam (DRE). During a DRE, a healthcare provider estimates the size, shape, and texture of the gland, providing a preliminary assessment of enlargement. While the DRE is a quick initial tool, it is not the most precise method for measuring volume.
The most accurate method is the Transrectal Ultrasound (TRUS), often considered the gold standard. A TRUS uses sound waves to create detailed images, allowing precise measurement of the three dimensions: length, width, and height. These measurements are then applied to a mathematical calculation, typically the ellipsoid formula, to determine the volume in cubic centimeters.
Primary Reasons for Prostate Enlargement
The most common reason for non-cancerous prostate growth is Benign Prostatic Hyperplasia (BPH). This condition is highly prevalent, affecting roughly half of all men by their 50s and up to 90% of men over age 80. BPH involves the excessive growth, or hyperplasia, of cells within the prostate gland’s transitional zone.
The development of BPH is closely linked to aging and specific hormonal changes. A primary factor is dihydrotestosterone (DHT), a potent active metabolite of testosterone. An enzyme called 5-alpha reductase converts circulating testosterone into DHT within the prostate cells. DHT binds to androgen receptors, stimulating the proliferation of epithelial and stromal cells. This sustained stimulation causes the gland to gradually increase in size over decades.
Urinary Symptoms Related to Increased Volume
As the prostate increases in size, it can compress the urethra, leading to bladder outlet obstruction. This obstruction disrupts the normal flow of urine and causes Lower Urinary Tract Symptoms (LUTS), which are categorized into voiding and storage issues.
Voiding symptoms stem directly from the narrowed urethra and include hesitancy (difficulty starting flow) and a weak or intermittent stream. Men may also experience post-void dribbling or the sensation that the bladder has not completely emptied. Storage symptoms relate to the bladder’s reaction to the obstruction, manifesting as frequency (urinating more often) and urgency (a sudden, strong need to urinate). A common complaint is nocturia, which is waking up multiple times during the night to urinate.