From the Guidelines
The normal size of the prostate gland is approximately 20-30 grams or about the size of a walnut, with a volume of less than 30cc on imaging. This size is considered normal because a prostate volume of >30cc is often used as a criterion for demonstrable prostatic enlargement, as stated in the AUA guideline for the management of lower urinary tract symptoms attributed to benign prostatic hyperplasia 1. The prostate gland's size can be assessed through a digital rectal exam or imaging studies like transrectal ultrasound.
- Key factors to consider when evaluating prostate size include:
- Age: the prostate naturally grows with age, with about half of men experiencing some prostate enlargement by age 60
- Symptoms: urinary symptoms such as frequency, urgency, weak stream, or incomplete emptying can be caused by an enlarged prostate compressing the urethra
- Imaging: transrectal ultrasound can provide precise measurements of prostate volume
- It's essential to note that the severity of symptoms doesn't always correlate directly with prostate size, as some men with significantly enlarged prostates may have minimal symptoms, while others with mild enlargement might experience considerable discomfort, as discussed in the context of combination therapy for lower urinary tract symptoms 1.
From the FDA Drug Label
The mean prostate volume as measured by transrectal ultrasound was 36.3 mL (±20.1 mL). Prostate volume was ≤20 mL in 16% of patients, ≥50 mL in 18% of patients and between 21 and 49 mL in 66% of patients Mean prostate volume at baseline ranged between 40 to 50 cc.
The normal size of the prostate gland is between 20 to 50 mL in terms of volume, with a mean size of around 36.3 mL to 40-50 cc. 2
From the Research
Prostate Gland Size
The normal size of the prostate gland can vary depending on age and other factors.
- According to a study published in 1984 3, the normal prostate reaches 20 ± 6 gm in men between 21 and 30 years old.
- A study published in 2003 4 found that the mean prostate volume was 40.1 ± 23.9 cm³ in men with lower urinary tract symptoms due to benign prostatic enlargement.
- Another study published in 2011 5 reported a mean prostate volume of 42cc and a median volume of 35cc in Ethiopian males above 40 years.
Age-Related Changes
Prostate volume tends to increase with age, but the rate of growth decreases with increasing age.
- A study published in 2007 6 found that the average percentage increase of total prostate volume per year of follow-up was 2.2%.
- The same study found that prostate volume was related to age only, and that the future prostate volume of an individual can be predicted based on his age and known history of prostate volume.
- A study published in 2003 4 found a statistically significant but weak correlation between prostate volume and age (r = 0.25, p < 0.0001).
Comparison of Measurement Methods
Different measurement methods can yield varying results for prostate size.
- A study published in 1998 7 found that digital rectal examination (DRE) underestimated prostate size compared to transrectal ultrasound (TRUS) measurement, with an average underestimation of 9-12% for prostate volumes 30-39 mL and 17-27% for prostate volumes 40-49 mL.