Possible biological mechanisms for a relationship between vasectomy and prostatic cancer.

Four hypotheses have been reviewed, each of which might serve as a hypothetical biological explanation for a relationship between vasectomy and prostate cancer. The endocrine hypothesis is the only one of these with any firm data to support it, although the majority of the available data does not lend credibility to that theory. The other hypotheses are purely speculative with no hard data to support them. In conclusion, it seems highly unlikely, but not impossible, that there is a biological mechanism supporting a relationship between vasectomy and prostate cancer.