The prostate and seminal vesicles are androgen-sensitive organs and are small in hypogonadal patients. Their volumes increase under testosterone therapy. Testosterone induces their normal functions, as indicated by the appearance of seminal fluid. Well-substituted patients should have ejaculate volumes in the normal range (i.e. > 2 ml).
There is much concern about the effects oftestosterone with regard to the development of benign prostatic hyperplasia (BPH) and carcinoma of the prostate and this issue is specifically dealt with in Chapters 2 and 21. A widely accepted theory on the pathogenesis of BPH suggests that prostatic enlargement is mediated through the action of 5a-DHT and that these alterations are related to intraprostatic events rather than to increases in serum concentrations of testosterone or 5a-DHT (Meikle et al. 1997; Morgentaler et al. 1996; Nomura et al. 1988). Furthermore, estrogens may be involved in hormonal regulation of prostatic tissue (Thomas and Keeman 1994). Testosterone therapy increases prostate volume in hypogonadal men, but only to the prostate size seen in age-matched controls (Behre et al. 1994b). This is also the case in patients on scrotal testosterone treatment leading to somewhat elevated serum DHT levels. However, as in other androgen target organs, the androgen receptor modifies testosterone action in the prostate as well. Thus, under the same testosterone therapy patients with shorter CAG repeats may develop larger prostates than men with longer CAG repeats (Zitzmann et al. 2003). Those with shorter CAG repeats may also be more likely develop prostate cancer (see Chapter 2 and 12). These findings have, however, not yet been translated into clinical practice.
PSA levels increase slightly during therapy but remain within the normal range of a younger population (Behre et al. 1994b; Meikle et al. 1997; von Eckardstein and Nieschlag 2002). PSA levels must be monitored regularly under testosterone therapy. Though limited in accuracy, sensitivity and specificity, rectal palpation of the prostate for size, surface and consistency belongs to the regular check-up of patients under testosterone treatment. Palpation may be assisted by transrectal ultrasonography of the prostate.
Because of the incidence of benign prostatic hyperplasia and prostate carcinoma increasing with age and the risk of stimulating the growth of a preexisting carcinoma by testosterone, patients should be examined carefully before onset of testosterone therapy and thereafter at annual intervals if under 45 years of age. In addition, in patients over 45 PSA levels and prostate palpation should be performed 3, 6 and 12 months after initiation of testosterone therapy since it may activate a preexisting carcinoma. If a carcinoma is diagnosed, testosterone treatment is contraindicated and must be terminated immediately.
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