Purpose: We attempted to determine the clinical and biological charact
eristics of familial benign prostatic hyperplasia (BPH). Materials and
Methods: Urinary flow rate, prostate size, symptom score, serum prost
ate specific antigen, testosterone and dihydrotestosterone were measur
ed in subjects who participated in the nationwide Merck phase III fina
steride clinical trial. Findings in the 69 men with familial BPH (3 or
more family members with BPH, including the proband) were compared to
those in the 345 with no family history of BPH. Logistic regression w
as used to detect relationships between familial BPH, and these variab
les before and after 5 alpha-reductase inhibition with finasteride. Re
sults: Familial BPH was characterized by large prostate size. Mean pro
state volume in men with familial and sporadic BPH was 82.7 and 55.5 m
l., respectively (p < 0.001). Other clinical findings, including serum
androgen levels and response to finasteride, were similar in familial
and sporadic BPH. The frequency of familial BPH in patients with pros
tate size in the largest and smallest deciles was 46 and 13%, respecti
vely. Conclusions: Familial BPH in this group of patients was associat
ed with large prostate size, normal serum androgen levels and normal r
esponse to 5 alpha-reductase inhibition. A genetic factor responsible
for familial BPH may exert its influence through androgen independent
control of prostatic growth.