One of the more common questions heard in urology clinic is, "Did I do something wrong to get a big prostate?" The answer is an emphatic, "No." We explain why below.
First, benign prostatic hyperplasia (BPH) and associated lower urinary tract symptoms (LUTS) are incredibly common:
- Approximately 40% of 50-year old men with have histologic evidence of BPH at autopsy, this number increases to 80% for 80-year men.
- Over the same time period, mean prostate volume increases 10-15 grams from an average baseline of 15-25 grams at age 50 to 25-40 grams at age 80.
- The percentage of men with moderate-to-severe LUTS varies among studies and countries, but definitely increases with age. 
Second, BPH is demonstrated to have a very strong heritable component. Some of the seminal work on the inheritance of BPH is discussed next.
In 1994, Dr. Martin Sanda examined 909 consecutive patients who underwent simple prostatectomy for benign disease at the Johns Hopkins Hospital. After investigating the families of these patients, he determined that:
- Male relatives of men with early-onset BPH (<64 years-old) had a 66% lifetime risk of prostatectomy for BPH; compared to 17% for controls (p=0.001).
- There was a 4-fold increase in age-specific risk of prostatectomy for BPH in men who underwent prostatectomy for BPH (p=0.003).
- The risk of prostatectomy for BPH increased to 6-fold for brothers of affected men (p=0.0089).
- Segregration analyses indicated a most-likely, autosomal dominant inheritance pattern. 
- The pairwise concordance for monozygotic (MZ, identical) twins was 14.7% and only 4.5% for dizygotic (DZ, fraternal) twins.
- The relative risk for MZ twins was therefore 3.3 (p=0.008).
- Therefore, up to 49% of observed variance between twins could be attributed to genetic causes in covariance analyses. 
|Journal of Urology, 1997; 157(3), 876-879.|