I see a contradiction. High testosterone level is not associated with prostate cancer. If there is an association, it's with a high carb diet and this kind of diet actually reduces testosterone level. It also increases estrogen level in men. In the bodybuilding world, they use various drugs that can both increase testosterone level and decrease estrogen level in men. It's the same drugs used for women to either reduce estrogen directly, or prevent estrogen to plug into cell receptors. They're called SERMs and AIs, selective estrogen receptor modulator, and aromatase inhibitor.
In men, estrogen is produced by converting testosterone to estrogen with the enzyme aromatase. Testosterone level is also regulated by estrogen in a negative feedback loop. Inhibiting the production of aromatase will therefore reduce the conversion, reduce estrogen, and increase testosterone. SERMs act by plugging into the estrogen receptor in the brain (I forget which part, it's one of the HPTA thingy), prevent estrogen from doing its job there, and effectively tell the brain there isn't enough estrogen, which will in turn cause a higher secretion of the hormone that tells the gonads to secrete and release more testosterone, in an attempt to produce more of the substrate from which estrogen is made.
As we can imagine, if something causes estrogen to rise in men, it will naturally cause testosterone to drop. But the point here is that direct testosterone replacement therapy will in fact cause a disruption in this negative feedback loop. There are many other alternatives, all of which are actually more effective. Another women-specific drug is used, it's HCG. It mimics LH at the gonads, and directly stimulates testosterone production. However, recently there's an even more effective drug, this one a peptide called triptorelin, which acts at the HPTA, and apparently restores natural testosterone production with a single low dose.
As for the prostate cancer risk, it's not exactly associated with testosterone directly, instead it's associated with DHT or dihydrotestosterone, a derivative of testosterone. It is produced by the conversion of testosterone through another enzyme, this one called 5alpha-reductase. There's a few drugs used here, the most famous is Finasteride. Incidentally, DHT is also involved in male baldness. So if they're worried about prostate cancer with testosterone therapy, they can just use a DHT inhibitor.
Furthermore, the conventional testosterone replacement therapy by direct injection will invariably involve having higher-than-normal testosterone at the time of injection, and lower-than-normal testosterone level just prior to injection. This is due to the protocol and the type of testosterone mix used. Though recently, there's been a few advances in the type of testosterone such that it would be possible to inject only every month of less, and still have close-to-normal testosterone level. If constant normal testosterone level is of most import, then the most appropriate therapy is with SERMs, AIs, perhaps HCG, maybe triptorelin.
http://en.wikipedia.org/wiki/Testosterone
http://en.wikipedia.org/wiki/Select...eptor_modulator
http://en.wikipedia.org/wiki/Aromatase_inhibitor
http://en.wikipedia.org/wiki/HPTA
http://en.wikipedia.org/wiki/Testos...acement_therapy
http://en.wikipedia.org/wiki/Triptorelin
http://en.wikipedia.org/wiki/Dihydrotestosterone