The prostate is a small, walnut-sized gland located deep within the male pelvis, immediately below the bladder. It completely encircles the initial part of the urethra, the tube that carries urine out of the body. Its primary function is producing fluid that nourishes and transports sperm, forming a significant portion of seminal fluid. As individuals age, the prostate commonly changes size. This article explains how the prostate is measured clinically, defines normal size, and details the symptoms and causes associated with size changes.
Understanding Prostate Measurement
Clinicians focus on the prostate’s volume or mass rather than simple linear dimensions, as volume is a more precise metric for tracking changes. While a healthy prostate is roughly 4 cm wide, 3 cm high, and 2 cm thick, linear measurements are less precise. Doctors calculate volume in cubic centimeters (cc) or milliliters (mL), which correlates closely with weight in grams (g). The most common method for accurate measurement is Transrectal Ultrasound (TRUS), though Magnetic Resonance Imaging (MRI) is also used. Volume is calculated by treating the prostate as an ellipsoid shape using the formula: length × width × height × 0.52, providing a standardized measurement for assessing enlargement.
Defining Normal and Enlarged Size
In a healthy young adult, the prostate typically weighs between 15 and 25 grams, corresponding to a volume of 20 to 30 cubic centimeters (cc). This baseline size often increases gradually throughout later decades of life due to age-related growth. An enlarged prostate, known as Benign Prostatic Hyperplasia (BPH), is generally defined as a volume exceeding 30 cc. For clinical purposes, enlargement is categorized: 30 to 50 cc is mild to moderate, 50 to 80 cc is moderately enlarged, and volumes exceeding 80 cc are considered severely enlarged. However, the absolute size of the prostate does not perfectly correlate with the severity of a person’s symptoms.
Symptoms Linked to Changes in Size
The impact of prostate enlargement is determined by the resulting symptoms, collectively known as Lower Urinary Tract Symptoms (LUTS). LUTS are categorized into storage and voiding symptoms. As the prostate grows, it presses on the urethra, causing an obstruction that affects the bladder’s ability to fill and empty. Voiding (obstructive) symptoms occur when the flow of urine is inhibited by the enlarged gland. These include:
- A slow or weak urinary stream.
- Hesitancy (difficulty initiating urination).
- Intermittency (the stream stops and starts).
- Straining to push urine out.
- Post-void dribbling (leakage immediately after finishing).
Storage (irritative) symptoms relate to the bladder’s reaction to the obstruction. These issues include urinary frequency, urgency (a sudden, compelling need to empty the bladder), and nocturia (waking up multiple times at night to urinate).
Causes of Prostate Growth and Next Steps
Causes of Prostate Growth
The underlying reason for age-related prostate growth involves hormonal changes. Benign Prostatic Hyperplasia (BPH) is a non-cancerous condition driven primarily by the potent androgen dihydrotestosterone (DHT). DHT is an active metabolite of testosterone, converted locally within the prostate by the enzyme 5-alpha-reductase. Although circulating testosterone levels may decrease with age, the local concentration of DHT remains high, stimulating the proliferation of glandular and stromal cells. This hormonal action leads to the hyperplastic growth characterizing BPH, which is considered a normal part of the aging process affecting most individuals over 50.
Next Steps and Diagnosis
If a person experiences LUTS symptoms, they should consult a healthcare professional. Initial evaluation often includes a Digital Rectal Examination (DRE) to estimate the prostate’s size and consistency, and a Prostate-Specific Antigen (PSA) blood test. Diagnostic steps may involve a uroflowmetry test to measure urinary flow speed and volume, and a measurement of Post-Void Residual (PVR) volume to determine how much urine remains after emptying. Symptom severity is assessed using a standardized questionnaire, like the International Prostate Symptom Score (IPSS), which guides the choice between watchful waiting, medication, or surgical intervention.