ABSTRACT
The prostate is a hormone-dependent organ. Its growth is stimulated and its size and secretory function are maintained by the continued presence of serum testosterone at approximately eugonadal male levels. Testosterone in the circulation is largely bound to proteins. Approximately 60% is bound to sex hormone-binding globulin (SHBG) and around 38% more loosely to albumin. Only 2-3% of circulating testosterone is unbound and diffuses into organs. Thereafter, it is subjected to a variety of steroid metabolic steps that regulate activity, and finally the inactivation of the steroid hormone. Over 95% of testosterone that enters the prostate is converted to 5α-dihydrotestosterone (DHT)1. DHT binds to the same hormone receptor as testosterone, but its biopotency is considerably higher. There is an abundance of androgen receptors in the prostate, probably more than in any other tissue2. The result is that the prostate is capable of accumulating testosterone, and local concentrations of androgens are approximately ten times higher than in the circulation. In the adult prostate, androgens continuously play a role in the maintenance of the gland in the mature and differentiated state by homeostatic mechanisms that are androgen-dependent. Prostate size and plasma levels of prostate-specific antigen (PSA) are decreased in androgen-deficient men, and increase again with androgen replacement, but not significantly exceeding the size and PSA levels in age-matched controls3-5.
