Reduced circulating androgen bioactivity in patients with prostate cancer

BACKGROUND: Previous studies on immunoreactive androgen levels in serum have revealed equivocal associations with the risk of prostate cancer (CaP). The aim of this study was to compare serum biological androgen activity between men with newly diagnosed CaP and age-matched men with benign prostatic hyperplasia (BPH). METHODS: Caucasian men with newly diagnosed, untreated CaP (n = 101) and age-matched patients with BPH (n = 103) were investigated. Serum androgen bioactivity (ABA) levels were measured using a recently developed recombinant cell bioassay. RESULTS: In comparison to men with BPH, CaP patients with Gleason score >or=8 (n = 16) had lower serum ABA (P < 0.05), and patients with Gleason score or=8 (P = 0.07) displayed suppressed ABA levels in relation to serum testosterone. As the entire group, men with CaP (n = 101) had significantly lower serum ABA than age-matched men with BPH (n = 103): median 3.0 nM (range, 0.8-6.4 nM) versus 3.2 nM (range, 0.8-7.9 nM) testosterone equivalents, respectively (P < 0.005). By contrast, serum immunoreactive testosterone and SHBG concentrations and free androgen indices did not differ significantly between the two groups. CONCLUSIONS: Patients with CaP have lower serum ABA than controls with BPH, and men with low or high Gleason score display suppressed circulating ABA-to-testosterone ratio. These features may reflect interaction between variables such as the degree of tumor differentiation and tumor volume with androgen metabolism.