Testosterone Measurement and Prostate Cancer

Testosterone is important growth factor for prostate cells. If testosterone availability drops, prostate cells stop thriving. Benign prostate shrinks and the same happens with prostate cancer cells. Larger decrease in testosterone availability means larger reduction in prostate cells mass. Although only reduction in testosterone levels will not, in most occasions, per‐ manently heal prostate cancer, it causes its regression and significantly delays further pro‐ gression of prostate cancer. Therefore, reduction of body's testosterone level is important prostate cancer treatment modality. When surgical removal of prostate due to cancer is not an opinion (for example because of advanced age, significant comorbidity or because cancer has already spread beyond prostate) or was unsuccessful as noted by rising PSA, which in‐ dicates cancer growth, serum testosterone value becomes very important factor in treatment related decisions. If testosterone values are high, reduction of testosterone level will be help‐ ful – it is expected prostate cells will react, shrink, PSA will fall. If testosterone values are already low, their further reduction with different agent may be possible. If testosterone val‐ ues are already at the lowest reachable levels, other ways of treatment should be sought. Af‐ ter reduction of testosterone levels in the body (castration), prostate cancer cells with time (sometimes months, sometimes years, sometimes decades) develop alternative signaling mechanisms and ways of paracrine androgens supply. It is estimated this happens in a third of all prostate cancer patients [1].