Plasma estradiol, free testosterone, sex hormone binding globulin binding capacity, and prolactin in benign prostatic hyperplasia and prostatic cancer.

The nature of hormonal changes with age and the possible role of these changes in the development of benign prostatic hyperplasia (BPH) and prostatic cancer (PC) were studied by assaying the plasma levels of total and free testosterone (T), estradiol (E2), prolactin, and sex hormone binding globulin binding capacity (SHBG) in 20 normal healthy men aged 40-59 years, in 30 patients with BPH aged 63-79 years, and in 30 patients with PC of similar height, weight, and age as the BPH patients. The mean E2 was highly significantly (P less than 0.0005) lower in the PC patients and in the young controls than in the BPH patients. The mean free T was significantly higher in the young controls than in the BPH patients (P less than 0.025) and PC patients (P less than 0.0005). The PC patients had a slightly lower (P less than 0.05) mean free T and mean E2/free T ratio than the BPH patients. The mean E2/free T ratio was significantly higher in the BPH patients (P less than 0.0005) and in the PC patients (P less than 0.0025) than in the young controls. It seems possible that the observed age-dependent significant increase in plasma estrogen concentration in the BPH patients may act as a protective factor against prostatic cancer.