Influence of age and endocrine factors on the volume of benign prostatic hyperplasia. To determine whether endocrine factors influence the volume of benign prostatic hyperplasia (BPH), 23 hormonal factors were measured in the serum of 64 men ages 42 to 71 years with low volume prostatic cancer and these levels were correlated with the volume of benign hyperplastic tissue in their radical prostatectomy specimens. With age there was a significant increase in the volume of BPH. Also with age there was a significant decrease in the serum levels of free testosterone, androstenedione, dehydroepiandronsterone (DHA), dehydroepiandronsterone sulphate (DHA-S), delta 5-androstenediol, and 17-hydroxypregnenolone, and a significant increase in sex hormone-binding globulin (SHBG), LH, and FSH. When BPH volume and hormone levels were corrected for age, BPH volume correlated positively with free testosterone, estradiol, and estriol. These data indicate that with age patients with larger volumes of BPH have higher serum androgen and estrogen levels suggesting that serum androgen and estrogen levels may be factors in the persistent stimulation of BPH with age. If so, therapeutic attempts at lowering plasma testosterone levels, reducing estrogen levels, or blocking androgenic stimulation through other mechanisms may interfere with the progression of BPH with age. Conversely, the fact that androgen production declines gradually with age may explain the observation that only 20 to 30% of men who live to age 80 require surgical treatment for urinary obstruction from BPH. 